Swing/SimpleSyntaxHighlight のバックアップ(No.9)

//This code is taken from:
//http://www.discoverteenergy.com/Files/SyntaxDocument.java SyntaxDocument.java
class SimpleSyntaxDocument extends DefaultStyledDocument {
  HashMap<String,AttributeSet> keywords = new HashMap<>();
  MutableAttributeSet normal = new SimpleAttributeSet();
  public SimpleSyntaxDocument() {
    super();
    StyleConstants.setForeground(normal, Color.BLACK);
    MutableAttributeSet color;
    StyleConstants.setForeground(color = new SimpleAttributeSet(), Color.RED);
    keywords.put("red", color);
    StyleConstants.setForeground(color = new SimpleAttributeSet(), Color.GREEN);
    keywords.put("green", color);
    StyleConstants.setForeground(color = new SimpleAttributeSet(), Color.BLUE);
    keywords.put("blue", color);
  }
  @Override public void insertString(int offset, String str, AttributeSet a)
                                               throws BadLocationException {
    super.insertString(offset, str, a);
    processChangedLines(offset, str.length());
  }
  @Override public void remove(int offset, int length)
                                               throws BadLocationException {
    super.remove(offset, length);
    processChangedLines(offset, 0);
  }
  private void processChangedLines(int offset, int length)
                                               throws BadLocationException {
    Element root   = getDefaultRootElement();
    String content = getText(0, getLength());
    int startLine  = root.getElementIndex( offset );
    int endLine    = root.getElementIndex( offset + length );
    for (int i = startLine; i <= endLine; i++) {
      applyHighlighting(content, i);
    }
  }
  private void applyHighlighting(String content, int line)
                                               throws BadLocationException {
    Element root = getDefaultRootElement();
    int startOffset   = root.getElement( line ).getStartOffset();
    int endOffset   = root.getElement( line ).getEndOffset() - 1;
    int lineLength  = endOffset - startOffset;
    int contentLength = content.length();
    if (endOffset >= contentLength) endOffset = contentLength - 1;
    setCharacterAttributes(startOffset, lineLength, normal, true);
    checkForTokens(content, startOffset, endOffset);
  }
  private void checkForTokens(String content, int startOffset, int endOffset) {
    while (startOffset <= endOffset) {
      while (isDelimiter(content.substring(startOffset, startOffset+1))) {
        if (startOffset < endOffset) {
          startOffset++;
        } else {
          return;
        }
      }
      startOffset = getOtherToken(content, startOffset, endOffset);
    }
  }
  private int getOtherToken(String content, int startOffset, int endOffset) {
    int endOfToken = startOffset + 1;
    while ( endOfToken <= endOffset ) {
      if ( isDelimiter( content.substring(endOfToken, endOfToken + 1) ) ) {
        break;
      }
      endOfToken++;
    }
    String token = content.substring(startOffset, endOfToken);
    if ( keywords.containsKey( token ) ) {
      setCharacterAttributes(
        startOffset, endOfToken - startOffset, keywords.get(token), false);
    }
    return endOfToken + 1;
  }
  String operands = ".,";
  protected boolean isDelimiter(String character) {
    return Character.isWhitespace(character.charAt(0)) ||
           operands.indexOf(character)!=-1;
  }
}