Kotlin

Java

btn.setSelected((i & (1 << 2)) != 0);

Kotlin(自動変換)

btn.setSelected(i and (1 shl 2) != 0)
// 以下のように誤変換される場合がある？？？
// 再現しないので勘違いかもしれない
// btn.setSelected(i and (1 shl 2 != 0))

Java

Box box = Box.createVerticalBox();
for (Component c: Arrays.<Component>asList(textField1, textField2, combo3, combo4)) {
  box.add(c);
  box.add(Box.createVerticalStrut(5));
}
// for (Component c: Arrays.asList(...)) { でも同じ変換結果になる

Kotlin(自動変換)

val box = Box.createVerticalBox()
for (c in Arrays.asList(textField1, textField2, combo3, combo4)) {
  box.add(c)
  box.add(Box.createVerticalStrut(5))
}
// error: none of the following functions can be called with the arguments supplied:
// public open fun add(p0: Component!): Component! defined in javax.swing.Box
// public open fun add(p0: PopupMenu!): Unit defined in javax.swing.Box
//             box.add(c)
//                 ^

Kotlin(手動修正)

val box = Box.createVerticalBox()
for (c in Arrays.asList<Component>(textField1, textField2, combo3, combo4)) {
  box.add(c);
  box.add(Box.createVerticalStrut(5));
}
// or:
// for (c in listOf<Component>(textField1, textField2, combo3, combo4)) {
// for (c in Arrays<Component>.asList(textField1, textField2, combo3, combo4)) {

Java

class CalendarViewTableModel<T extends LocalDate> extends DefaultTableModel {
  public CalendarViewTableModel(T date) {

Kotlin(自動変換)

class CalendarViewTableModel<T : LocalDate> public constructor(date: T) : DefaultTableModel() {

Java

enabledCheck.addActionListener(e -> {
  Container c = SwingUtilities.getAncestorOfClass(JComboBox.class, this);
  if (c instanceof JComboBox) {
    JComboBox<?> combo = (JComboBox<?>) c;
    ComboItem item = (ComboItem) combo.getItemAt(data.getIndex());
    item.setEnabled(((JCheckBox) e.getSource()).isSelected());
    editableCheck.setEnabled(item.isEnabled());
    textField.setEnabled(item.isEnabled());
  }
});

Kotlin(自動変換)

enabledCheck.addActionListener({ e ->
  val c = SwingUtilities.getAncestorOfClass(JComboBox<*>::class.java, this)
  if (c is JComboBox<*>) {
    val combo = c as JComboBox<*>
    val item = combo.getItemAt(data.index) as ComboItem
    item.isEnabled = (e.getSource() as JCheckBox).isSelected()
    editableCheck.setEnabled(item.isEnabled)
    textField.setEnabled(item.isEnabled)
  }
})

Kotlin(手動修正)

enabledCheck.addActionListener {
  val c = SwingUtilities.getAncestorOfClass(JComboBox::class.java, this)
  if (c is JComboBox<*>) {
    val item = c.getItemAt(data.index) as ComboItem
    item.isEnabled = (e.getSource() as JCheckBox).isSelected()
    editableCheck.setEnabled(item.isEnabled)
    textField.setEnabled(item.isEnabled)
  }
}

Java

class CheckBoxList<E extends CheckBoxNode> extends JList<E> {
  private transient CheckBoxCellRenderer<E> renderer;
  protected CheckBoxList(ListModel<E> model) {
    super(model);
  }
  @Override public void updateUI() {
    setForeground(null);
    setBackground(null);
    setSelectionForeground(null);
    setSelectionBackground(null);
    removeMouseListener(renderer);
    removeMouseMotionListener(renderer);
    super.updateUI();
    renderer = new CheckBoxCellRenderer<>();
    setCellRenderer(renderer);
    addMouseListener(renderer);
    addMouseMotionListener(renderer);
    putClientProperty("List.isFileList", Boolean.TRUE);
  }
  // ...
}

Kotlin(自動変換)

internal class CheckBoxList<E : CheckBoxNode> protected constructor(model: ListModel<E>) : JList<E>(model) {
  @Transient
  private var renderer: CheckBoxCellRenderer<E>? = null

  override fun updateUI() {
    setForeground(null)
    setBackground(null)
    setSelectionForeground(null)
    setSelectionBackground(null)
    removeMouseListener(renderer)
    removeMouseMotionListener(renderer)
    super.updateUI()
    renderer = CheckBoxCellRenderer<example.CheckBoxNode>()
    // renderer = CheckBoxCellRenderer<CheckBoxNode>() // でもType mismatchでエラー
    setCellRenderer(renderer)
    addMouseListener(renderer)
    addMouseMotionListener(renderer)
    putClientProperty("List.isFileList", java.lang.Boolean.TRUE)
  }
  // ...
}

Kotlin(手動修正)

internal class CheckBoxList<E : CheckBoxNode> protected constructor(model: ListModel<E>) : JList<E>(model) {
  @Transient
  private var renderer: CheckBoxCellRenderer<E>? = null

  override fun updateUI() {
    setForeground(null)
    setBackground(null)
    setSelectionForeground(null)
    setSelectionBackground(null)
    removeMouseListener(renderer)
    removeMouseMotionListener(renderer)
    super.updateUI()
    renderer = CheckBoxCellRenderer<E>()
    // renderer = CheckBoxCellRenderer<>() // NG
    // renderer = CheckBoxCellRenderer() // OK
    setCellRenderer(renderer)
    addMouseListener(renderer)
    addMouseMotionListener(renderer)
    putClientProperty("List.isFileList", java.lang.Boolean.TRUE)
  }
  // ...
}

Java

tree.addTreeWillExpandListener(new TreeWillExpandListener() {
  @Override public void treeWillExpand(TreeExpansionEvent e)
      throws ExpandVetoException {
    //throw new ExpandVetoException(e, "Tree expansion cancelled");
  }
  @Override public void treeWillCollapse(TreeExpansionEvent e)
      throws ExpandVetoException {
    throw new ExpandVetoException(e, "Tree collapse cancelled");
  }
});

Kotlin(自動変換)

tree.addTreeWillExpandListener(object : TreeWillExpandListener() {
  @Throws(ExpandVetoException::class)
  override fun treeWillExpand(e: TreeExpansionEvent) {
    // throw new ExpandVetoException(e, "Tree expansion cancelled");
  }
  @Throws(ExpandVetoException::class)
  override fun treeWillCollapse(e: TreeExpansionEvent) {
    throw ExpandVetoException(e, "Tree collapse cancelled")
  }
})

Kotlin(手動修正)

tree.addTreeWillExpandListener(object : TreeWillExpandListener {
  @Throws(ExpandVetoException::class)
  override fun treeWillExpand(e: TreeExpansionEvent) {
    // throw new ExpandVetoException(e, "Tree expansion cancelled");
  }
  @Throws(ExpandVetoException::class)
  override fun treeWillCollapse(e: TreeExpansionEvent) {
    throw ExpandVetoException(e, "Tree collapse cancelled")
  }
})

Java

JButton decode = new JButton("decode");
decode.addActionListener(e -> {
  String b64 = textArea.getText();
  if (b64.isEmpty()) {
    return;
  }
  try (InputStream is = ...) {
    label.setIcon(new ImageIcon(ImageIO.read(is)));
  } catch (IOException ex) {
    ex.printStackTrace();
  }
});

Kotlin(自動変換)

val decode = JButton("decode")
decode.addActionListener({ e ->
  val b64 = textArea.getText()
  if (b64.isEmpty()) {
    return@decode.addActionListener
  }
  try {
    // ...
  } catch (ex: IOException) {
    ex.printStackTrace()
  }
})

Kotlin(手動修正)

val decode = JButton("decode")
decode.addActionListener {
  val b64 = textArea.getText()
  if (b64.isEmpty()) {
    return@addActionListener
  }
  try {
    // ...
  } catch (ex: IOException) {
    ex.printStackTrace()
  }
}

Java

BufferedImage bi = Optional.ofNullable(getClass().getResource("unkaku_w.png"))
    .map(url -> {
      try {
        return ImageIO.read(url);
      } catch (IOException ex) {
        return makeMissingImage();
      }
    }).orElseGet(() -> makeMissingImage());

Kotlin(自動変換)

val bi = Optional.ofNullable(javaClass.getResource("unkaku_w.png")).map({ url ->
  try {
    return@Optional.ofNullable(getClass().getResource("unkaku_w.png")).map ImageIO . read url
  } catch (ex: IOException) {
    return@Optional.ofNullable(getClass().getResource("unkaku_w.png")).map makeMissingImage ()
  }
}).orElseGet({ makeMissingImage() })

Kotlin(手動修正1)

val bi = Optional.ofNullable(javaClass.getResource("unkaku_w.png")).map { url ->
  try {
    ImageIO.read(url)
  } catch (ex: IOException) {
    makeMissingImage()
  }
}.orElseGet { makeMissingImage() }

Kotlin(手動修正2)

val bi = javaClass.getResource("unkaku_w.png")?.let {
  try {
    ImageIO.read(it)
  } catch (ex: IOException) {
    makeMissingImage()
  }
} ?: makeMissingImage()

Kotlin(手動修正3)

// runCatching関数でResultを取得するようtry-catchを置き換える
val bi = runCatching {
  ImageIO.read(javaClass.getResource("unkaku_w.png"))
}.getOrNull() ?: makeMissingImage()

Java

public static Stream<TreeNode> descendants(TreeNode node) {
  Class<TreeNode> clz = TreeNode.class;
  return Collections.list((Enumeration<?>) node.children())
    .stream().filter(clz::isInstance).map(clz::cast);
}

Kotlin(自動変換)

fun descendants(node: TreeNode): Stream<TreeNode> {
  val clz = TreeNode::class.java
  return Collections.list(node.children() as Enumeration<*>)
    .stream().filter(???({ clz!!.isInstance() })).map(clz!!.cast)
}

Kotlin(手動修正)

fun descendants(node: TreeNode): Stream<TreeNode> {
  val clz = TreeNode::class.java
  return Collections.list(node.children() as Enumeration<*>)
    .stream().filter(clz::isInstance).map(clz::cast)
    // .filterIsInstance(clz).stream()
}

Kotlin(手動修正): Iterable<*>.filterIsInstance()が便利

fun descendants(node: TreeNode): List<TreeNode> {
  return (node.children() as Enumeration<*>)
    .toList().filterIsInstance(TreeNode::class.java)
}

Java

public static Stream<Component> stream(Container parent) {
  return Stream.of(parent.getComponents())
    .filter(Container.class::isInstance)
    .map(c -> stream(Container.class.cast(c)))
    .reduce(Stream.of(parent), Stream::concat);
  }

Kotlin(自動変換)

// 自動的に以下のimportは生成されないのでunresolved referenceになる
// import java.util.function.BinaryOperator
// import java.util.function.Predicate
fun stream(parent: Container): Stream<Component> {
  return Stream.of(*parent.getComponents())
    .filter(Predicate<Component> { Container::class.java!!.isInstance(it) })
    .map({ c -> stream(Container::class.java!!.cast(c)) })
    .reduce(Stream.of(parent), BinaryOperator<Stream<Component>> { a, b -> Stream.concat(a, b) })
}

Kotlin(手動修正)

import java.util.function.BinaryOperator
import java.util.function.Predicate
fun stream(parent: Container): Stream<Component> {
  // return Stream.of(*parent.getComponents())
  return Arrays.asList(parent.getComponents())
    .filter(Container::class.java::isInstance)
    .map { c -> stream(Container::class.java.cast(c)) }
    // OK: .reduce(Stream.of(parent), BinaryOperator<Stream<Component>>{ a, b -> Stream.concat(a, b) })
    // NG: .reduce(Stream.of(parent), Stream::concat)
    .reduce(Stream.of<Component>(parent), { a, b -> Stream.concat<Component>(a, b) }) // OK
}

Kotlin(手動修正)

// Stream を Iterable に変換してしまう方法もある
fun descendants(parent: Container): List<Component> {
  return parent.getComponents().toList()
    .filterIsInstance(Container::class.java)
    .map { descendants(it) }
    .fold(listOf<Component>(parent)) { a, b -> a + b }
}
// ...
descendants(fileChooser1)
  .filterIsInstance(JTable::class.java)
  // .firstOrNull()?.apply(JTable::removeEditor)
  .firstOrNull()?.let { table ->
    println(table)
    table.removeEditor()
  }

Java

JPanel p = new JPanel(new GridLayout(0, 1, 2, 2));
Arrays.asList(button1, button2).forEach(p::add);

Kotlin(自動変換)

val p = JPanel(GridLayout(0, 1, 2, 2))
Arrays.asList(button1, button2).forEach( ?? ? ({ p.add() }))

Kotlin(手動修正)

val p = JPanel(GridLayout(0, 1, 2, 2))
listOf(button1, button2).forEach { b -> p.add(b) }
//or listOf(button1, button2).map(p::add)

Java

Stream.of("A", "B", "C").map(JToggleButton::new).forEach(r -> {
  p.add(r);
  bg.add(r);
});

Kotlin(自動変換)

Stream.of("A", "B", "C").map(Function<String, JToggleButton> { JToggleButton(it) }).forEach({ r ->
  p.add(r)
  bg.add(r)
})

Kotlin(手動修正)

Stream.of("A", "B", "C").map(::JToggleButton).forEach { r ->
  p.add(r)
  bg.add(r)
}

Java

double d = delta.y * GRAVITY;
int ia = (int) d;
int ib = (int) Math.floor(d);
int ic = new BigDecimal(d).setScale(0, RoundingMode.DOWN).intValue();
System.out.format("%d %d %d%n", ia, ib, ic);

Kotlin(自動変換)

val d = delta.y * GRAVITY
val ia = d.toInt()
val ib = Math.floor(d) as Int
val ic = BigDecimal(d).setScale(0, RoundingMode.DOWN).intValue()
System.out.format("%d %d %d%n", ia, ib, ic)

Kotlin(手動修正)

val d = delta.y * GRAVITY
val ia = d.toInt()
val ib = Math.floor(d).toInt()
val ic = BigDecimal(d).setScale(0, RoundingMode.DOWN).toInt()
println("${ia} ${ib} ${ic}")

Java

import java.util.*;
public class SortTest {
  public static void main(String[] args) {
    List<List<Integer>> list = Arrays.asList(
      Arrays.asList(15, 20, 35),
      Arrays.asList(30, 45, 72),
      Arrays.asList(15, 20, 31),
      Arrays.asList(27, 33, 59),
      Arrays.asList(27, 35, 77));
    list.sort(Comparator.<List<Integer>>comparingInt(l -> l.get(0))
      .thenComparingInt(l -> l.get(1))
      .thenComparingInt(l -> l.get(2))
      .reversed());
    System.out.println(list);
  }
}

Kotlin(自動変換)

fun main(args: Array<String>) {
  val list = Arrays.asList(
    Arrays.asList(15, 20, 35),
    Arrays.asList(30, 45, 72),
    Arrays.asList(15, 20, 31),
    Arrays.asList(27, 33, 59),
    Arrays.asList(27, 35, 77))
  list.sort(Comparator.comparingInt({ l -> l.get(0) })
    .thenComparingInt({ l -> l.get(1) })
    .thenComparingInt({ l -> l.get(2) })
    .reversed())
  System.out.println(list)
}

Kotlin(手動修正)

fun main(args: Array<String>) {
  val list = Arrays.asList(
    Arrays.asList(15, 20, 35),
    Arrays.asList(30, 45, 72),
    Arrays.asList(15, 20, 31),
    Arrays.asList(27, 33, 59),
    Arrays.asList(27, 35, 77))
  list.sortWith(Comparator.comparingInt<List<Int>> { l -> l.get(0) }
    .thenComparingInt { l -> l.get(1) }
    .thenComparingInt { l -> l.get(2) }
    .reversed())
  System.out.println(list)
}

Kotlin(手動修正)

fun main(args: Array<String>) {
  val list = listOf<List<Int>>(
    listOf(15, 20, 35),
    listOf(30, 45, 72),
    listOf(15, 20, 31),
    listOf(27, 33, 59),
    listOf(27, 35, 77))
  val l = list.sortedWith(compareBy({ it.get(0) }, { it.get(1) }, { it.get(2) })).reversed()
  println(l)
}

Java

editor1.setSelectionColor(new Color(0x64_88_AA_AA, true)); // IntelliJで自動変換できない
editor2.setSelectionColor(new Color(0x6488AAAA, true)); // IntelliJで自動変換可能

Kotlin(手動修正)

editor1.setSelectionColor(Color(0x64_88_AA_AA, true)) // 問題なし
editor2.setSelectionColor(Color(0x6488AAAA, true)) // 問題なし

Java

class RowHeaderRenderer<E> extends JLabel implements ListCellRenderer<E> {
  private final JTableHeader header; // = table.getTableHeader();

  public RowHeaderRenderer(JTableHeader header) {
    super();
    this.header = header;
    this.setOpaque(true);
    // ...

Kotlin(旧自動変換)

inner class RowHeaderRenderer<E>(private val header: JTableHeader // = table.getTableHeader();) : JLabel(), ListCellRenderer<E> {

  init {
    this.setOpaque(true)
    // ...

Kotlin(新自動変換)

inner class RowHeaderRenderer<E>(private val header: JTableHeader // = table.getTableHeader();
) : JLabel(), ListCellRenderer<E> {

  init {
    this.setOpaque(true)
    // ...

Java

Color argb = new Color(0xffaabbcc, true);
Color rgb = new Color(0xaabbcc);

Kotlin(自動変換)

val argb = Color(-0x554434, true)
val rgb = Color(0xaabbcc)

Kotlin(手動修正)

// LongからIntに変換する方法もある
val argb = Color(0xff_aa_bb_cc.toInt(), true)
println(argb == Color(-0x554434, true)) // true

Java

@SuppressWarnings("unchecked")
WatchEvent<Path> ev = (WatchEvent<Path>) event;

Kotlin(手動修正)

@Suppress("UNCHECKED_CAST")
val ev = event as WatchEvent<Path>

Java

private final Integer[][] mask;
@SuppressWarnings("PMD.UseVarargs")
protected SudokuCellRenderer(Integer[][] src) {
  super();
  Integer[][] dest = new Integer[src.length][src[0].length];
  for (int i = 0; i < src.length; i++) {
    System.arraycopy(src[i], 0, dest[i], 0, src[0].length);
  }
  this.mask = dest;
}

Kotlin(自動変換)

private val mask: Array<Array<Int>>
init {
  val dest = Array<Array<Int>>(src.size) { arrayOfNulls(src[0].size) }
  for (i in src.indices) {
    System.arraycopy(src[i], 0, dest[i], 0, src[0].size)
  }
  this.mask = dest
}

Kotlin(手動修正1)

private val mask: Array<Array<Int?>>
init {
  val dest = Array<Array<Int?>>(src.size) { arrayOfNulls(src[0].size) }
  // もしくはval mask: Array<Array<Int>>のままで、適当なInt値で初期化
  // val dest = Array(src.size, { Array(src[0].size, { 0 }) }) // 0で初期化
  for (i in src.indices) {
    System.arraycopy(src[i], 0, dest[i], 0, src[0].size)
  }
  this.mask = dest
}

Kotlin(手動修正2)

private val mask: Array<Array<Int>>
init {
  // System.arraycopyなどは使用せず、コピー元の二次元配列を参照して初期化
  this.mask = Array(src.size, { i -> Array(src[i].size, { j -> src[i][j] }) })
}

Java

import java.awt.geom.Ellipse2D;

enum ButtonLocation {
  CENTER(0d),
  NORTH(45d),
  EAST(135d),
  SOUTH(225d),
  WEST(-45d);
  private final double degree;
  ButtonLocation(double degree) {
    this.degree = degree;
  }

  public double getStartAngle() {
    return degree;
  }
}
// ...
Shape inner = new Ellipse2D.Double(xx, xx, ww, ww);

Kotlin(自動変換)

import java.awt.geom.Ellipse2D.Double

enum class ButtonLocation(val startAngle: kotlin.Double) {
  CENTER(0.0), NORTH(45.0), EAST(135.0), SOUTH(225.0), WEST(-45.0);
}
// ...
val inner: Shape = Double(xx, xx, ww, ww)

Kotlin(手動修正)

import java.awt.geom.Ellipse2D

enum class ButtonLocation(val startAngle: Double) {
  CENTER(0.0), NORTH(45.0), EAST(135.0), SOUTH(225.0), WEST(-45.0);
}

val inner: Shape = Ellipse2D.Double(xx, xx, ww, ww)

Java

Set<?> f = v instanceof Set ? (Set<?>) v : EnumSet.noneOf(Permissions.class);

Kotlin

val f = v as? Set<*> ?: EnumSet.noneOf(Permissions::class.java)

Java

class FileListTable extends JTable {
  private class RubberBandingListener extends MouseAdapter {
    @Override public void mousePressed(MouseEvent e) {
      FileListTable table = FileListTable.this
      // ...

Kotlin

class FileListTable(model: TableModel) : JTable(model) {
  private inner class RubberBandingListener : MouseAdapter() {
    override fun mousePressed(e: MouseEvent) {
      val table = this@FileListTable
      // ...

Java

checkBox.setSelected(node.getStatus() == Status.SELECTED);

Kotlin

checkBox.setSelected(it.status === Status.SELECTED)

Java

Container p = SwingUtilities.getAncestorOfClass(JViewport.class, this);
if (!(p instanceof JViewport)) {
  return;
}

Kotlin

val p = SwingUtilities.getAncestorOfClass(JViewport::class.java, this) as? JViewport ?: return

Java

import java.awt.*;
import javax.swing.*;
import javax.swing.table.*;

public class JTableExample {
  public JComponent makeUI() {
    String[] cn = {"String", "Integer", "Boolean"};
    Object[][] data = {
      {"aaa", 12, true}, {"bbb", 5, false},
      {"CCC", 92, true}, {"DDD", 0, false}
    };
    TableModel m = new DefaultTableModel(data, cn) {
      @Override public Class<?> getColumnClass(int col) {
        return getValueAt(0, col).getClass();
      }
    };
    JTable table = new JTable(m);
    table.setAutoCreateRowSorter(true);

    JPanel p = new JPanel(new BorderLayout());
    p.add(new JScrollPane(table));
    return p;
  }
  public static void main(String... args) {
    EventQueue.invokeLater(() -> {
      JFrame f = new JFrame();
      f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      f.add(new JTableExample().makeUI());
      f.setSize(320, 240);
      f.setLocationRelativeTo(null);
      f.setVisible(true);
    });
  }
}

Kotlin

import java.awt.*
import javax.swing.*
import javax.swing.table.*

fun makeUI(): JComponent {
  val cn = arrayOf("String", "Integer", "Boolean")
  val data = arrayOf(
    arrayOf("aaa", 12, true), arrayOf("bbb", 5, false),
    arrayOf("CCC", 92, true), arrayOf("DDD", 0, false))
  val m = object: DefaultTableModel(data, cn) {
    override fun getColumnClass(col: Int): Class<Any> {
      return getValueAt(0, col).javaClass
    }
  }
  // val m = object: DefaultTableModel(data, cn) {
  //   override fun getColumnClass(col: Int): Class<*> {
  //     return when (col) {
  //       0 -> String::class.java
  //       1 -> Integer::class.java
  //       // XXX: 2 -> Boolean::class.java
  //       2 -> java.lang.Boolean::class.java
  //       else -> Object::class.java
  //     }
  //   }
  // }
  val table = JTable(m).apply {
    autoCreateRowSorter = true
  }
  return JPanel(BorderLayout(5, 5)).apply {
    add(JScrollPane(table))
  }
}
fun main(args: Array<String>) {
  EventQueue.invokeLater {
    JFrame("kotlin swing").apply {
      defaultCloseOperation = JFrame.EXIT_ON_CLOSE
      add(makeUI())
      size = Dimension(320, 240)
      setLocationRelativeTo(null)
      setVisible(true)
    }
  }
}

Java

import java.awt.*;
import java.util.*;
import javax.swing.*;

public class JTreeExample {
  public JComponent makeUI() {
    JTree tree = new JTree();

    JButton b1 = new JButton("expand");
    b1.addActionListener(e -> expandAll(tree));

    JButton b2 = new JButton("collapse");
    b2.addActionListener(e -> collapseAll(tree));

    JPanel pp = new JPanel(new GridLayout(1, 0, 5, 5));
    Arrays.asList(b1, b2).forEach(pp::add);
    JPanel p = new JPanel(new BorderLayout(5, 5));
    p.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
    p.add(new JScrollPane(tree));
    p.add(pp, BorderLayout.SOUTH);
    return p;
  }
  protected static void expandAll(JTree tree) {
    int row = 0;
    while (row < tree.getRowCount()) {
      tree.expandRow(row);
      row++;
    }
  }
  protected static void collapseAll(JTree tree) {
    int row = tree.getRowCount() - 1;
    while (row >= 0) {
      tree.collapseRow(row);
      row--;
    }
  }
  public static void main(String[] args) {
    EventQueue.invokeLater(() -> {
      JFrame f = new JFrame();
      f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      f.add(new JTreeExample().makeUI());
      f.setSize(320, 240);
      f.setLocationRelativeTo(null);
      f.setVisible(true);
    });
  }
}

Kotlin

import java.awt.*
import javax.swing.*

fun makeUI(): JComponent {
  val tree = JTree()
  val p = JPanel(GridLayout(1, 0, 5, 5)).apply {
    add(JButton("expand").apply {
      addActionListener { expandAll(tree) }
    })
    add(JButton("collapse").apply {
      addActionListener { collapseAll(tree) }
    })
  }
  return JPanel(BorderLayout(5, 5)).apply {
    setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5))
    add(JScrollPane(tree))
    add(p, BorderLayout.SOUTH)
  }
}
fun expandAll(tree: JTree) {
  var row = 0
  while (row < tree.getRowCount()) {
    tree.expandRow(row)
    row++
  }
}
fun collapseAll(tree : JTree) {
  var row = tree.getRowCount() - 1
  while (row >= 0) {
    tree.collapseRow(row)
    row--
  }
}
fun main(args: Array<String>) {
  EventQueue.invokeLater {
    JFrame("kotlin swing").apply {
      defaultCloseOperation = JFrame.EXIT_ON_CLOSE
      add(makeUI())
      size = Dimension(320, 240)
      setLocationRelativeTo(null)
      setVisible(true)
    }
  }
}

Java

import java.awt.*;
import javax.swing.*;

public class JCheckBoxExample {
  public JComponent makeUI() {
    JCheckBox cb = new JCheckBox("Always On Top", true);
    cb.addActionListener(e -> {
      AbstractButton b = (AbstractButton) e.getSource();
      Container c = b.getTopLevelAncestor();
      if (c instanceof Window) {
        ((Window) c).setAlwaysOnTop(b.isSelected());
      }
    });
    JPanel p = new JPanel(new BorderLayout());
    p.add(cb, BorderLayout.NORTH);
    return p;
  }
  public static void main(String[] args) {
    EventQueue.invokeLater(() -> {
      JFrame f = new JFrame();
      f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      f.add(new JCheckBoxExample().makeUI());
      f.setSize(320, 240);
      f.setLocationRelativeTo(null);
      f.setVisible(true);
    });
  }
}

Kotlin

import java.awt.*
import javax.swing.*

fun makeUI(): JComponent {
  val cb = JCheckBox("Always On Top", true).apply {
//     addActionListener { e ->
//       val c = e.getSource()
//       if (c is AbstractButton) {
//         val w = c.getTopLevelAncestor()
//         if (w is Window) {
//           w.setAlwaysOnTop(c.isSelected())
//         }
//       }
    addActionListener { e ->
      val b = e.getSource() as AbstractButton
      val w = b.getTopLevelAncestor()
      if (w is Window) {
        w.setAlwaysOnTop(b.isSelected())
      }
    }
//     addActionListener {
//       val w = getTopLevelAncestor()
//       if (w is Window) {
//           w.setAlwaysOnTop(isSelected())
//       }
//     }
  }
  return JPanel(BorderLayout()).apply {
    add(cb, BorderLayout.NORTH)
  }
}

fun main(args: Array<String>) {
  EventQueue.invokeLater {
    JFrame("kotlin swing").apply {
      defaultCloseOperation = JFrame.EXIT_ON_CLOSE
      add(makeUI())
      size = Dimension(320, 240)
      setLocationRelativeTo(null)
      setVisible(true)
    }
  }
}

Java

import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.plaf.*;
import javax.swing.table.*;

public final class MainPanel {
  public JComponent makeUI() {
    String[] columnNames = {"user", "rwx"};
    Object[][] data = {
      {"owner", 7}, {"group", 6}, {"other", 5}
    };
    TableModel model = new DefaultTableModel(data, columnNames) {
      @Override public Class<?> getColumnClass(int column) {
        return getValueAt(0, column).getClass();
      }
    };
    JTable table = new JTable(model) {
      @Override public void updateUI() {
        super.updateUI();
        getColumnModel().getColumn(1).setCellRenderer(new CheckBoxesRenderer());
        getColumnModel().getColumn(1).setCellEditor(new CheckBoxesEditor());
      }
    };
    table.putClientProperty("terminateEditOnFocusLost", Boolean.TRUE);

    JPanel p = new JPanel(new BorderLayout());
    p.add(new JScrollPane(table));
    return p;
  }
  public static void main(String[] args) {
    EventQueue.invokeLater(() -> {
      JFrame frame = new JFrame();
      frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
      frame.getContentPane().add(new MainPanel().makeUI());
      frame.setSize(320, 240);
      frame.setLocationRelativeTo(null);
      frame.setVisible(true);
    });
  }
}

class CheckBoxesPanel extends JPanel {
  protected static final String[] TITLES = {"r", "w", "x"};
  public JCheckBox[] buttons;
  @Override public void updateUI() {
    super.updateUI();
    setOpaque(false);
    setBackground(new Color(0x0, true));
    setLayout(new BoxLayout(this, BoxLayout.X_AXIS));
    initButtons();
  }
  private void initButtons() {
    buttons = new JCheckBox[TITLES.length];
    for (int i = 0; i < buttons.length; i++) {
      JCheckBox b = new JCheckBox(TITLES[i]);
      b.setOpaque(false);
      b.setFocusable(false);
      b.setRolloverEnabled(false);
      b.setBackground(new Color(0x0, true));
      buttons[i] = b;
      add(b);
      add(Box.createHorizontalStrut(5));
    }
  }
  protected void updateButtons(Object v) {
    removeAll();
    initButtons();
    Integer i = v instanceof Integer ? (Integer) v : 0;
    buttons[0].setSelected((i & (1 << 2)) != 0);
    buttons[1].setSelected((i & (1 << 1)) != 0);
    buttons[2].setSelected((i & (1 << 0)) != 0);
  }
}

class CheckBoxesRenderer extends CheckBoxesPanel implements TableCellRenderer {
  @Override public void updateUI() {
    super.updateUI();
    setName("Table.cellRenderer");
  }
  @Override public Component getTableCellRendererComponent(JTable table, Object value, boolean isSelected, boolean hasFocus, int row, int column) {
    updateButtons(value);
    return this;
  }
}

class CheckBoxesEditor extends AbstractCellEditor implements TableCellEditor {
  private final CheckBoxesPanel panel = new CheckBoxesPanel() {
    @Override public void updateUI() {
      super.updateUI();
      EventQueue.invokeLater(() -> {
        ActionMap am = getActionMap();
        for (int i = 0; i < buttons.length; i++) {
          String title = TITLES[i];
          am.put(title, new AbstractAction(title) {
            @Override public void actionPerformed(ActionEvent e) {
              Arrays.stream(buttons)
              .filter(b -> b.getText().equals(title))
              .findFirst()
              .ifPresent(JCheckBox::doClick);
              fireEditingStopped();
            }
          });
        }
        InputMap im = getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW);
        im.put(KeyStroke.getKeyStroke(KeyEvent.VK_R, 0), TITLES[0]);
        im.put(KeyStroke.getKeyStroke(KeyEvent.VK_W, 0), TITLES[1]);
        im.put(KeyStroke.getKeyStroke(KeyEvent.VK_X, 0), TITLES[2]);
      });
    }
  };
  @Override public Component getTableCellEditorComponent(JTable table, Object value, boolean isSelected, int row, int column) {
    panel.updateButtons(value);
    return panel;
  }
  @Override public Object getCellEditorValue() {
    int i = 0;
    i = panel.buttons[0].isSelected() ? 1 << 2 | i : i;
    i = panel.buttons[1].isSelected() ? 1 << 1 | i : i;
    i = panel.buttons[2].isSelected() ? 1 << 0 | i : i;
    return i;
  }
}

Kotlin

import java.awt.*
import java.awt.event.*
import java.util.*
import javax.swing.*
import javax.swing.event.*
import javax.swing.plaf.*
import javax.swing.table.*

fun makeUI(): JComponent {
  val columnNames = arrayOf("user", "rwx")
  val data = arrayOf(arrayOf<Any>("owner", 7), arrayOf<Any>("group", 6), arrayOf<Any>("other", 5))
  val model = object : DefaultTableModel(data, columnNames) {
    override fun getColumnClass(column: Int): Class<*> {
      return getValueAt(0, column).javaClass
    }
  }
  val table = object : JTable(model) {
    override fun updateUI() {
      super.updateUI()
      getColumnModel().getColumn(1).setCellRenderer(CheckBoxesRenderer())
      getColumnModel().getColumn(1).setCellEditor(CheckBoxesEditor())
    }
  }
  table.putClientProperty("terminateEditOnFocusLost", java.lang.Boolean.TRUE)
  return JPanel(BorderLayout(5, 5)).apply {
    add(JScrollPane(table))
  }
}

fun main(args: Array<String>) {
  EventQueue.invokeLater {
    JFrame("kotlin swing").apply {
      defaultCloseOperation = JFrame.EXIT_ON_CLOSE
      add(makeUI())
      size = Dimension(320, 240)
      setLocationRelativeTo(null)
      setVisible(true)
    }
  }
}

open class CheckBoxesPanel() : JPanel() {
  public val buttons = arrayOf(JCheckBox(Permission.READ.toString()), JCheckBox(Permission.WRITE.toString()), JCheckBox(Permission.EXECUTE.toString()))

  override fun updateUI() {
    super.updateUI()
    setOpaque(false)
    setBackground(Color(0x0, true))
    setLayout(BoxLayout(this, BoxLayout.X_AXIS))
    EventQueue.invokeLater({ initButtons() })
  }

  private fun initButtons() {
    for (b in buttons) {
      b.setOpaque(false)
      b.setFocusable(false)
      b.setRolloverEnabled(false)
      b.setBackground(Color(0x0, true))
      add(b)
      add(Box.createHorizontalStrut(5))
    }
  }

  public fun updateButtons(v: Any) {
    removeAll()
    initButtons()
    val i = v as ? Int ? : 0
    buttons[0].setSelected(i and (1 shl 2) != 0)
    buttons[1].setSelected(i and (1 shl 1) != 0)
    buttons[2].setSelected(i and (1 shl 0) != 0)
  }
}

enum class Permission(var str: String) {
  READ("r"), WRITE("w"), EXECUTE("x");
  override fun toString() = str
}

internal class CheckBoxesRenderer : CheckBoxesPanel(), TableCellRenderer {
  override fun updateUI() {
    super.updateUI()
    setName("Table.cellRenderer")
  }
  override fun getTableCellRendererComponent(table: JTable, value: Any, isSelected: Boolean, hasFocus: Boolean, row: Int, column: Int): Component {
    updateButtons(value)
    return this
  }
}

internal class CheckBoxesEditor : AbstractCellEditor(), TableCellEditor {
  private val panel = object : CheckBoxesPanel() {
    override fun updateUI() {
      super.updateUI()
      EventQueue.invokeLater({
        val am = getActionMap()
        for (i in buttons.indices) {
          val title = buttons[i].getText()
          am.put(title, object : AbstractAction(title) {
            override fun actionPerformed(e: ActionEvent) {
              Arrays.stream(buttons)
                .filter({ b -> b.getText() == title })
                .findFirst()
                .ifPresent({ it.doClick() })
              fireEditingStopped()
            }
          })
        }
        val im = getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW)
        im.put(KeyStroke.getKeyStroke(KeyEvent.VK_R, 0), Permission.READ.toString())
        im.put(KeyStroke.getKeyStroke(KeyEvent.VK_W, 0), Permission.WRITE.toString())
        im.put(KeyStroke.getKeyStroke(KeyEvent.VK_X, 0), Permission.EXECUTE.toString())
      })
    }
  }

  override fun getTableCellEditorComponent(table: JTable, value: Any, isSelected: Boolean, row: Int, column: Int): Component {
    panel.updateButtons(value)
    return panel
  }

  override fun getCellEditorValue(): Any {
    var i = 0
    i = if (panel.buttons[0].isSelected()) 1 shl 2 or i else i
    i = if (panel.buttons[1].isSelected()) 1 shl 1 or i else i
    i = if (panel.buttons[2].isSelected()) 1 shl 0 or i else i
    return i
  }
}

Java

protected ActionListener handler;
// ...
handler = e -> stopCellEditing();

Kotlin(自動変換)

protected var handler: ActionListener? = null
// ...
handler = { e -> stopCellEditing() }
// error: type mismatch: inferred type is (???) -> Boolean but ActionListener? was expected
//             handler = { e -> stopCellEditing() }
// error: cannot infer a type for this parameter. Please specify it explicitly.
//             handler = { e -> stopCellEditing() }
// error: modifier 'override' is not applicable to 'local function'
//               override fun actionPerformed(e: ActionEvent) : Unit {

Kotlin(手動修正)

protected var handler: ActionListener? = null
// ...
handler = ActionListener { stopCellEditing() }
// or:
handler = object: ActionListener {
  override fun actionPerformed(e: ActionEvent) : Unit { // Unitは無くても可
    stopCellEditing()
  }
}

Java

class CheckBoxNodeEditor extends AbstractCellEditor implements TreeCellEditor {
  @Override public Object getCellEditorValue() {
    return new CheckBoxNode(checkBox.getText(), checkBox.isSelected());
  }
  // ...

Kotlin(自動変換)

val cellEditorValue: Any
  override get() = CheckBoxNode(checkBox.getText(), checkBox.isSelected())
//error: modifier 'override' is not applicable to 'getter'
//       override get() = CheckBoxNode(checkBox.getText(), checkBox.isSelected())

Kotlin(手動修正)

  override fun getCellEditorValue(): Any {
    return CheckBoxNode(checkBox.getText(), checkBox.isSelected())
  }

Java

import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.tree.*;

public class LeafCheckBoxTreeTest {
  private JComponent makeUI() {
    JTree tree = new JTree();
    tree.setEditable(true);
    tree.setCellRenderer(new CheckBoxNodeRenderer());
    tree.setCellEditor(new CheckBoxNodeEditor());
    tree.setRowHeight(18);

    boolean b = true;
    TreeModel model = tree.getModel();
    DefaultMutableTreeNode root = (DefaultMutableTreeNode) model.getRoot();
    Enumeration<?> e = root.breadthFirstEnumeration();
    while (e.hasMoreElements()) {
      DefaultMutableTreeNode node = (DefaultMutableTreeNode) e.nextElement();
      String s = Objects.toString(node.getUserObject(), "");
      node.setUserObject(new CheckBoxNode(s, b));
      b ^= true;
    }
    return new JScrollPane(tree);
  }
  public static void main(String[] args) {
    EventQueue.invokeLater(() -> {
      UIManager.put("swing.boldMetal", Boolean.FALSE);
      JFrame f = new JFrame();
      f.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
      f.getContentPane().add(new LeafCheckBoxTreeTest().makeUI());
      f.setSize(320, 240);
      f.setLocationRelativeTo(null);
      f.setVisible(true);
    });
  }
}

class CheckBoxNodeRenderer implements TreeCellRenderer {
  private final JCheckBox checkBox = new JCheckBox();
  private final DefaultTreeCellRenderer renderer = new DefaultTreeCellRenderer();
  @Override public Component getTreeCellRendererComponent(
      JTree tree, Object value, boolean selected, boolean expanded,
      boolean leaf, int row, boolean hasFocus) {
    if (leaf && value instanceof DefaultMutableTreeNode) {
      checkBox.setEnabled(tree.isEnabled());
      checkBox.setFont(tree.getFont());
      checkBox.setOpaque(false);
      checkBox.setFocusable(false);
      Object userObject = ((DefaultMutableTreeNode) value).getUserObject();
      if (userObject instanceof CheckBoxNode) {
        CheckBoxNode node = (CheckBoxNode) userObject;
        checkBox.setText(node.text);
        checkBox.setSelected(node.selected);
      }
      return checkBox;
    }
    return renderer.getTreeCellRendererComponent(
        tree, value, selected, expanded, leaf, row, hasFocus);
  }
}

class CheckBoxNodeEditor extends AbstractCellEditor implements TreeCellEditor {
  private final JCheckBox checkBox = new JCheckBox() {
    protected transient ActionListener handler;
    @Override public void updateUI() {
      removeActionListener(handler);
      super.updateUI();
      setOpaque(false);
      setFocusable(false);
      handler = e -> stopCellEditing();
      addActionListener(handler);
    }
  };
  @Override public Component getTreeCellEditorComponent(
      JTree tree, Object value, boolean selected, boolean expanded,
      boolean leaf, int row) {
    if (leaf && value instanceof DefaultMutableTreeNode) {
      Object userObject = ((DefaultMutableTreeNode) value).getUserObject();
      if (userObject instanceof CheckBoxNode) {
        checkBox.setSelected(((CheckBoxNode) userObject).selected);
      } else {
        checkBox.setSelected(false);
      }
      checkBox.setText(value.toString());
    }
    return checkBox;
  }
  @Override public Object getCellEditorValue() {
    return new CheckBoxNode(checkBox.getText(), checkBox.isSelected());
  }
  @Override public boolean isCellEditable(EventObject e) {
    if (e instanceof MouseEvent && e.getSource() instanceof JTree) {
      MouseEvent me = (MouseEvent) e;
      JTree tree = (JTree) me.getComponent();
      TreePath path = tree.getPathForLocation(me.getX(), me.getY());
      Object o = path.getLastPathComponent();
      if (o instanceof TreeNode) {
        return ((TreeNode) o).isLeaf();
      }
    }
    return false;
  }
}

class CheckBoxNode {
  public final String text;
  public final boolean selected;
  protected CheckBoxNode(String text, boolean selected) {
    this.text = text;
    this.selected = selected;
  }
  @Override public String toString() {
    return text;
  }
}

Kotlin

import java.awt.*
import java.awt.event.*
import java.util.*
import javax.swing.*
import javax.swing.event.*
import javax.swing.tree.*

private fun makeUI(): JComponent {
  val tree = JTree()
  tree.setEditable(true)
  tree.setCellRenderer(CheckBoxNodeRenderer())
  tree.setCellEditor(CheckBoxNodeEditor())
  tree.setRowHeight(18)

  var b = true
  val model = tree.getModel()
  val root = model.getRoot() as DefaultMutableTreeNode
  val e = root.breadthFirstEnumeration()
  while (e.hasMoreElements()) {
    val node = e.nextElement() as DefaultMutableTreeNode
    val s = Objects.toString(node.getUserObject(), "")
    node.setUserObject(CheckBoxNode(s, b))
    b = b xor true
  }
  return JScrollPane(tree)
}

fun main(args: Array<String>) {
  EventQueue.invokeLater {
    UIManager.put("swing.boldMetal", false)
    JFrame("kotlin swing").apply {
      defaultCloseOperation = JFrame.EXIT_ON_CLOSE
      add(makeUI())
      size = Dimension(320, 240)
      setLocationRelativeTo(null)
      setVisible(true)
    }
  }
}

internal class CheckBoxNodeRenderer : TreeCellRenderer {
  private val checkBox = JCheckBox()
  private val renderer = DefaultTreeCellRenderer()
  override fun getTreeCellRendererComponent(
    tree: JTree, value: Any, selected: Boolean, expanded: Boolean,
    leaf: Boolean, row: Int, hasFocus: Boolean): Component {
    if (leaf && value is DefaultMutableTreeNode) {
      checkBox.setEnabled(tree.isEnabled())
      checkBox.setFont(tree.getFont())
      checkBox.setOpaque(false)
      checkBox.setFocusable(false)
      val userObject = value.getUserObject()
      if (userObject is CheckBoxNode) {
        val node = userObject // as CheckBoxNode
        checkBox.setText(node.text)
        checkBox.setSelected(node.selected)
      }
      return checkBox
    }
    return renderer.getTreeCellRendererComponent(
      tree, value, selected, expanded, leaf, row, hasFocus)
  }
}

internal class CheckBoxNodeEditor : AbstractCellEditor(), TreeCellEditor {
  private val checkBox = object : JCheckBox() {
    protected var handler: ActionListener? = null
    override fun updateUI() {
      removeActionListener(handler)
      super.updateUI()
      setOpaque(false)
      setFocusable(false)
      // handler = object: ActionListener {
      //   override fun actionPerformed(e: ActionEvent) : Unit {
      //     stopCellEditing()
      //   }
      // }
      handler = ActionListener { stopCellEditing() }
      addActionListener(handler)
    }
  }

  override fun getTreeCellEditorComponent(
      tree: JTree, value: Any, selected: Boolean, expanded: Boolean,
      leaf: Boolean, row: Int): Component {
    if (leaf && value is DefaultMutableTreeNode) {
      val userObject = value.getUserObject()
      if (userObject is CheckBoxNode) {
        checkBox.setSelected(userObject.selected)
      } else {
        checkBox.setSelected(false)
      }
      checkBox.setText(value.toString())
    }
    return checkBox
  }

  override fun getCellEditorValue(): Any {
    return CheckBoxNode(checkBox.getText(), checkBox.isSelected())
  }

  override fun isCellEditable(e: EventObject): Boolean {
    if (e is MouseEvent && e.getSource() is JTree) {
      val tree = e.getComponent() as JTree
      val path = tree.getPathForLocation(e.getX(), e.getY())
      val o = path.getLastPathComponent()
      if (o is TreeNode) {
        return o.isLeaf()
      }
    }
    return false
  }
}

internal class CheckBoxNode public constructor(val text: String, val selected: Boolean) {
  override fun toString(): String {
    return text
  }
}

Java

import java.awt.*;
import java.text.*;
import java.util.*;
import javax.swing.*;
import javax.swing.text.*;

public class OptionalExample {
  private JComponent makeUI() {
    SimpleDateFormat format = new SimpleDateFormat(
        "mm:ss, SSS", Locale.getDefault());
    DefaultFormatterFactory factory = new DefaultFormatterFactory(
        new DateFormatter(format));

    Calendar calendar = Calendar.getInstance();
    calendar.set(Calendar.HOUR_OF_DAY, 0);
    calendar.clear(Calendar.MINUTE);
    calendar.clear(Calendar.SECOND);
    calendar.clear(Calendar.MILLISECOND);
    Date d = calendar.getTime();

    JSpinner sp1 = new JSpinner(new SpinnerDateModel(
        d, null, null, Calendar.SECOND));
    JSpinner.DefaultEditor ed1 = (JSpinner.DefaultEditor) sp1.getEditor();
    ed1.getTextField().setFormatterFactory(factory);

    HashMap<Integer, Integer> stepSizeMap = new HashMap<>();
    stepSizeMap.put(Calendar.HOUR_OF_DAY, 1);
    stepSizeMap.put(Calendar.MINUTE,      1);
    stepSizeMap.put(Calendar.SECOND,      30);
    stepSizeMap.put(Calendar.MILLISECOND, 500);

    JSpinner sp2 = new JSpinner(new SpinnerDateModel(
        d, null, null, Calendar.SECOND) {
      @Override public Object getPreviousValue() {
        Calendar cal = Calendar.getInstance();
        cal.setTime(getDate());
        Integer calendarField = getCalendarField();
        Integer stepSize = Optional.ofNullable(
            stepSizeMap.get(calendarField)).orElse(1);
        cal.add(calendarField, -stepSize);
        return cal.getTime();
      }
      @Override public Object getNextValue() {
        Calendar cal = Calendar.getInstance();
        cal.setTime(getDate());
        Integer calendarField = getCalendarField();
        Integer stepSize = Optional.ofNullable(
            stepSizeMap.get(calendarField)).orElse(1);
        cal.add(calendarField, stepSize);
        return cal.getTime();
      }
    });
    JSpinner.DefaultEditor ed2 = (JSpinner.DefaultEditor) sp2.getEditor();
    ed2.getTextField().setFormatterFactory(factory);

    JPanel p = new JPanel();
    p.add(sp1);
    p.add(sp2);
    return p;
  }
  public static void main(String... args) {
    EventQueue.invokeLater(() -> {
      JFrame f = new JFrame();
      f.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
      f.getContentPane().add(new OptionalExample().makeUI());
      f.setSize(320, 240);
      f.setLocationRelativeTo(null);
      f.setVisible(true);
    });
  }
}

Kotlin

import java.awt.*
import java.text.*
import java.util.*
import javax.swing.*
import javax.swing.text.*

fun makeUI(): JComponent {
  val format = SimpleDateFormat("mm:ss, SSS", Locale.getDefault())
  val factory = DefaultFormatterFactory(DateFormatter(format))

  val calendar = Calendar.getInstance().apply {
    set(Calendar.HOUR_OF_DAY, 0)
    clear(Calendar.MINUTE)
    clear(Calendar.SECOND)
    clear(Calendar.MILLISECOND)
  }
  val d = calendar.getTime()

  val sp1 = JSpinner(SpinnerDateModel(d, null, null, Calendar.SECOND))
  val ed1 = sp1.getEditor()
  if (ed1 is JSpinner.DefaultEditor) {
    ed1.getTextField().setFormatterFactory(factory)
  }

  val stepSizeMap: HashMap<Int, Int> = hashMapOf(
      Calendar.HOUR_OF_DAY to 1,
      Calendar.MINUTE      to 1,
      Calendar.SECOND      to 30,
      Calendar.MILLISECOND to 500)

  val sp2 = JSpinner(object: SpinnerDateModel(d, null, null, Calendar.SECOND) {
    override fun getPreviousValue(): Any = Calendar.getInstance().apply {
      time = getDate()
      val stepSize = stepSizeMap.get(calendarField).let { it } ?: 1
      add(calendarField, -stepSize)
    }.getTime()
    override fun getNextValue(): Any = Calendar.getInstance().apply {
        setTime(getDate())
        val stepSize = stepSizeMap.get(calendarField).let { it } ?: 1
        add(calendarField, stepSize)
    }.getTime()
  })
  val ed2 = sp2.getEditor()
  if (ed2 is JSpinner.DefaultEditor) {
    ed2.getTextField().setFormatterFactory(factory)
  }

  return JPanel().apply {
    add(sp1)
    add(sp2)
  }
}

fun main(args: Array<String>) {
  EventQueue.invokeLater {
    JFrame("kotlin swing").apply {
      defaultCloseOperation = WindowConstants.EXIT_ON_CLOSE
      add(makeUI())
      size = Dimension(320, 240)
      setLocationRelativeTo(null)
      setVisible(true)
    }
  }
}

Java

public final class MainPanel extends JPanel {
  private final JSpinner spinner = new JSpinner();
  @Override public void updateUI() {
    super.updateUI();
    Long lv = Optional.ofNullable(spinner)
        .map(s -> (Long) s.getModel().getValue())
        .orElse(1000L);
    // Long lv = spinner != null ? (Long) spinner.getModel().getValue() : 1000L;
    // ...
  }

Kotlin

class MainPanel : JPanel(BorderLayout()) {
  private val spinner = JSpinner()
  private val spinner: JSpinner? = JSpinner()
  override fun updateUI() {
    super.updateUI()
    val lv = Optional.ofNullable(spinner)
        .map { it.getModel().getValue() }
        .orElse(1000L)

    // Unnecessary safe call on a non-null receiver of type JSpinner
    // val lv = spinner
    //     ?.let { it.getModel().getValue() }
    //     ?: 1000L

    // NullPointerException
    // val lv = spinner.getModel().getValue()

    // Condition 'spinner != null' is always 'true'
    // val lv = if (spinner != null) spinner.getModel().getValue() else 1000L

    // private val spinner: JSpinner? = JSpinner() なら(他の個所もspinner?にすれば)以下でOK
    // val lv = spinner?.getModel()?.getValue() ?: 1000L
  }

Kotlin 自動変換

import java.awt.* // ktlint-disable no-wildcard-imports
import java.awt.event.MouseEvent
import java.util.EventObject
import javax.swing.* // ktlint-disable no-wildcard-imports
import javax.swing.event.AncestorEvent
import javax.swing.event.AncestorListener
import javax.swing.tree.DefaultMutableTreeNode
import javax.swing.tree.DefaultTreeCellEditor
import javax.swing.tree.DefaultTreeCellRenderer
import javax.swing.tree.TreePath

class MainPanel : JPanel(BorderLayout()) {
  init {
    val tree = JTree()
    tree.cellEditor = object : DefaultTreeCellEditor(tree, tree.cellRenderer as? DefaultTreeCellRenderer) {
      override fun isCellEditable(e: EventObject) = e !is MouseEvent && super.isCellEditable(e)
    }
    tree.isEditable = true
    tree.componentPopupMenu = TreePopupMenu()
    add(JScrollPane(tree))
    preferredSize = Dimension(320, 240)
  }
}

class TreePopupMenu : JPopupMenu() {
  private var path: TreePath? = null
  private val editItem: JMenuItem
  private val editDialogItem: JMenuItem

  override fun show(c: Component, x: Int, y: Int) {
    (c as? JTree)?.also { tree ->
      val tsp = tree.selectionPaths
      path = tree.getPathForLocation(x, y)
      val isEditable = tsp != null && tsp.size == 1 && tsp[0] == path
      editItem.isEnabled = isEditable
      editDialogItem.isEnabled = isEditable
      super.show(c, x, y)
    }
  }

  init {
    val field = JTextField()
    field.addAncestorListener(FocusAncestorListener())
    editItem = add("Edit")
    editItem.addActionListener {
      path?.also {
        (invoker as? JTree)?.startEditingAtPath(it)
      }
    }
    editDialogItem = add("Edit Dialog")
    editDialogItem.addActionListener {
      (path?.lastPathComponent as? DefaultMutableTreeNode)?.also { node ->
        field.text = node.userObject.toString()
        (invoker as? JTree)?.also { tree ->
          val ret = JOptionPane.showConfirmDialog(
            tree, field, "Rename", JOptionPane.OK_CANCEL_OPTION, JOptionPane.PLAIN_MESSAGE
          )
          if (ret == JOptionPane.OK_OPTION) {
            tree.model.valueForPathChanged(path, field.text)
          }
        }
      }
    }
    add("dummy")
  }
}

class FocusAncestorListener : AncestorListener {
  override fun ancestorAdded(e: AncestorEvent) {
    e.component.requestFocusInWindow()
  }

  override fun ancestorMoved(e: AncestorEvent) {
    /* not needed */
  }

  override fun ancestorRemoved(e: AncestorEvent) {
    /* not needed */
  }
}

fun main() {
  EventQueue.invokeLater {
    runCatching {
      UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName())
    }.onFailure {
      it.printStackTrace()
      Toolkit.getDefaultToolkit().beep()
    }
    JFrame().apply {
      setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE)
      getContentPane().add(MainPanel())
      pack()
      setLocationRelativeTo(null)
      setVisible(true)
    }
  }
}

Kotlin 手動修正

import java.awt.* // ktlint-disable no-wildcard-imports
import java.awt.event.MouseEvent
import java.util.EventObject
import javax.swing.* // ktlint-disable no-wildcard-imports
import javax.swing.event.AncestorEvent
import javax.swing.event.AncestorListener
import javax.swing.tree.DefaultMutableTreeNode
import javax.swing.tree.DefaultTreeCellEditor
import javax.swing.tree.DefaultTreeCellRenderer
import javax.swing.tree.TreePath

class MainPanel : JPanel(BorderLayout()) {
  init {
    val tree = JTree()
    tree.cellEditor = object : DefaultTreeCellEditor(tree, tree.cellRenderer as? DefaultTreeCellRenderer) {
      override fun isCellEditable(e: EventObject) = e !is MouseEvent && super.isCellEditable(e)
    }
    tree.isEditable = true
    tree.componentPopupMenu = TreePopupMenu()
    add(JScrollPane(tree))
    preferredSize = Dimension(320, 240)
  }
}

class TreePopupMenu : JPopupMenu() {
  private var path: TreePath? = null
  private val editItem: JMenuItem
  private val editDialogItem: JMenuItem

  override fun show(c: Component, x: Int, y: Int) {
    (c as? JTree)?.also { tree ->
      val tsp = tree.selectionPaths
      path = tree.getPathForLocation(x, y)
      val isEditable = tsp != null && tsp.size == 1 && tsp[0] == path
      editItem.isEnabled = isEditable
      editDialogItem.isEnabled = isEditable
      super.show(c, x, y)
    }
  }

  init {
    val field = JTextField()
    field.addAncestorListener(FocusAncestorListener())
    editItem = add("Edit")
    editItem.addActionListener {
      path?.also {
        (invoker as? JTree)?.startEditingAtPath(it)
      }
    }
    editDialogItem = add("Edit Dialog")
    editDialogItem.addActionListener {
      (path?.lastPathComponent as? DefaultMutableTreeNode)?.also { node ->
        field.text = node.userObject.toString()
        (invoker as? JTree)?.also { tree ->
          val ret = JOptionPane.showConfirmDialog(
            tree, field, "Rename", JOptionPane.OK_CANCEL_OPTION, JOptionPane.PLAIN_MESSAGE
          )
          if (ret == JOptionPane.OK_OPTION) {
            tree.model.valueForPathChanged(path, field.text)
          }
        }
      }
    }
    add("JMenuItem")
  }
}

class FocusAncestorListener : AncestorListener {
  override fun ancestorAdded(e: AncestorEvent) {
    e.component.requestFocusInWindow()
  }

  override fun ancestorMoved(e: AncestorEvent) {
    /* not needed */
  }

  override fun ancestorRemoved(e: AncestorEvent) {
    /* not needed */
  }
}

fun main() {
  EventQueue.invokeLater {
    runCatching {
      UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName())
    }.onFailure {
      it.printStackTrace()
      Toolkit.getDefaultToolkit().beep()
    }
    JFrame().apply {
      setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE)
      getContentPane().add(MainPanel())
      pack()
      setLocationRelativeTo(null)
      setVisible(true)
    }
  }
}

val indices = IntStream.range(0, l.getModel().getSize())
    .filter { rb.intersects(l.getCellBounds(it, it)) }.toArray()

val indices = (0 until l.getModel().getSize())
    .filter { rb.intersects(l.getCellBounds(it, it)) }.toIntArray()

val lengthOfTask = 10 + Random().nextInt(50)

val lengthOfTask = (10..60).random()

var flag = 1
val keys = table.getRowSorter().getSortKeys()
if (!keys.isEmpty()) {
  val sortKey = keys.get(0)
  if (sortKey.getColumn() == column && sortKey.getSortOrder() == SortOrder.DESCENDING) {
    flag = -1
  }
}

val flag = table.getRowSorter().getSortKeys().firstOrNull()
    ?.takeIf { it.getColumn() == column && it.getSortOrder() == SortOrder.DESCENDING }
    ?.let { -1 } ?: 1

p.setComponentZOrder(p.getComponent(p.getComponentCount() - 1), 0)

p.setComponentZOrder(p.getComponents().last(), 0)

val clz = JTable::class.java
Optional.ofNullable(SwingUtilities.getAncestorOfClass(clz, e.getComponent()))
    .filter(clz::isInstance)
    .map(clz::cast)
    .filter(JTable::isEditing)
    .ifPresent(JTable::removeEditor)

SwingUtilities.getAncestorOfClass(JTable::class.java, e.getComponent())
    ?.takeIf { it is JTable }
    ?.let { it as JTable }
    ?.takeIf { it.isEditing() }
    ?.also{ it.removeEditor() }

// takeIf {...}内のitにはスマートキャストが効くが、それを越えて作用はしない
SwingUtilities.getAncestorOfClass(JTable::class.java, e.getComponent())
    ?.takeIf { it is JTable && it.isEditing() }
    ?.also { (it as JTable).removeEditor() }
    // ?.also { JTable::removeEditor } // コンパイルエラーにはならないが、removeEditor()メソッドは実行されない？

val lv = Optional.ofNullable(spinner).map { it.getModel().getValue() }.orElse(1000L)

val lv = spinner?.getModel()?.getValue() ?: 1000L

if (Objects.nonNull(colHead) && colHead.isVisible()) {
  val colHeadHeight = Math.min(availR.height, colHead.getPreferredSize().height)
  // ...
}

colHead?.takeIf { it.isVisible() }?.let {
  val colHeadHeight = Math.min(availR.height, it.getPreferredSize().height)
  // ...
}

Objects.requireNonNull(url)

requireNotNull(url)

fun stream(parent: Container): Stream<Component> = Arrays.stream(parent.getComponents())
    .filter(Container::class.java::isInstance)
    .map { c -> stream(Container::class.java.cast(c)) }
    .reduce(Stream.of<Component>(parent), { a, b -> Stream.concat<Component>(a, b) })

fun descendants(parent: Container): List<Component> = parent.getComponents()
    .filterIsInstance(Container::class.java)
    .map { descendants(it) }
    .fold(listOf<Component>(parent), { a, b -> a + b })

// // Java
// private Stream<MenuElement> descendants(MenuElement me) {
//   return Stream.of(me.getSubElements())
//     .flatMap(m -> Stream.concat(Stream.of(m), descendants(m)));
// }
fun descendants(me: MenuElement): Stream<MenuElement> {
  return Stream.of(*me.subElements)
    .flatMap { Stream.concat(Stream.of(it), descendants(it)) }
}

// StreamではなくIterableが使用可能
private fun descendants(me: MenuElement): List<MenuElement> =
  me.getSubElements().flatMap { listOf(it) + descendants(it) }

// // Java
// int max = group.stream()
//     .map(AlignedLabel::getSuperPreferredWidth)
//     .reduce(0, Integer::max);
val max = group.stream()
    .map(Function<AlignedLabel, Int> { it.getSuperPreferredWidth() })
    .reduce(0, BinaryOperator<Int> { a, b -> Integer.max(a, b) })

val max = group.stream()
    .map { it.getSuperPreferredWidth() }
    .reduce(0, Integer::max)

val max = group
    .map { it.getSuperPreferredWidth() }
    .fold(0) { a, b -> maxOf(a, b) }

val max = group.map { it.getSuperPreferredWidth() }.fold(0, ::maxOf)

// この例だとIntなのでmax()とエルビス演算子`?:`が使用可能
val max = group.map { it.getSuperPreferredWidth() }.max() ?: 0

val text = Collections.nCopies(2000, "aaaaaaaaaaaaa").joinToString("\n")

val text = "aaaaaaaaaaaaa\n".repeat(2000)

String msg = jlist.getSelectedValuesList().stream()
    .map(it -> it.title)
    .collect(Collectors.joining(", "));

val msg = jlist.selectedValuesList
    .map { it.title }
    .joinToString(", ")

// private List<AlignedLabel> group;
int max = group.stream()
    .map(AlignedLabel::getSuperPreferredWidth)
    .reduce(0, Integer::max);

// private var group = mutableListOf<AlignedLabel>()
// val max = group.map { it.getSuperPreferredWidth() }.fold(0, ::maxOf)
// val max = group.map { it.getSuperPreferredWidth() }.maxOrNull() ?: 0
// group.isNotEmpty()
val max = group.maxOf(AlignedLabel::getSuperPreferredWidth)

// private String makeTestHtml() {
//   return String.join("\n", strarray);
// }
// を自動変換すると以下のようなコードになる
private fun makeTestHtml(): String {
  return arrayOf(
    "<html><body>",
    "<div>2222222222</div>",
    "</body></html>").joinToString("\n")
}

// が、三重引用符で囲めば改行などをエスケープシーケンスで記入する必要はない
private fun makeTestHtml() = """
  <html>
    <body>
      <div>2222222222</div>
    </body>
  </html>
"""

// val tnc = Comparator.comparing(Function<DefaultMutableTreeNode, Boolean> { it.isLeaf() })
val tnc = Comparator.comparing<DefaultMutableTreeNode, Boolean> { it.isLeaf() }
    .thenComparing { n -> n.getUserObject().toString() }
val children = parent.children().toList()
    .filterIsInstance(DefaultMutableTreeNode::class.java)
    .sortedWith(tnc)

val tnc = compareBy<DefaultMutableTreeNode> { it.isLeaf() }
    .thenBy { it.getUserObject().toString() }
val children = parent.children().toList()
    .filterIsInstance(DefaultMutableTreeNode::class.java)
    .sortedWith(tnc)
    // .sortedWith(compareBy(DefaultMutableTreeNode::isLeaf, { it.getUserObject().toString() }))

// Only classes are allowed on the left hand side of a class literal
// とエラーになる
listOf(c0, c1, c2, c3)
  .mapNotNull { it.getModel() }
  .filterIsInstance(MutableComboBoxModel<String>::class.java)
  .forEach { it.insertElementAt(str, it.getSize()) }

// Type mismatch. でエラーになる
listOf(c0, c1, c2, c3)
  .mapNotNull { it.getModel() }
  .filterIsInstance(MutableComboBoxModel::class.java)
  .forEach { it.insertElementAt(str, it.getSize()) }

// reified type parameter を使用する
listOf(c0, c1, c2, c3)
  .mapNotNull { it.getModel() }
  .filterIsInstance<MutableComboBoxModel<String>>()
  .forEach { it.insertElementAt(str, it.getSize()) }

listOf(c0, c1, c2, c3)
  .mapNotNull { it.getModel() as? MutableComboBoxModel<String> }
  .forEach { it.insertElementAt(str, it.getSize()) }

interface ExpansionListener : EventListener {
   fun expansionStateChanged(e: ExpansionEvent)
 }
}
// ...
p.addExpansionListener(object : ExpansionListener {
  override fun expansionStateChanged(e: ExpansionEvent) {
    (e.source as? Component)?.also {
      // ...
    }
  }
})

fun interface ExpansionListener : EventListener {
   fun expansionStateChanged(e: ExpansionEvent)
 }
}
// ...
p.addExpansionListener { e ->
  (e.source as? Component)?.also {
    // ...
  }
}