Parentheses matcher
/*
Java Swing, 2nd Edition
By Marc Loy, Robert Eckstein, Dave Wood, James Elliott, Brian Cole
ISBN: 0-596-00408-7
Publisher: O'Reilly
*/
// ParenMatcher.java
//A simple parenthesis matcher.
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTextPane;
import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.SimpleAttributeSet;
import javax.swing.text.StyleConstants;
import javax.swing.text.StyleContext;
import javax.swing.text.StyledDocument;
public class ParenMatcher extends JTextPane implements Runnable {
public static Color[] matchColor = { Color.blue, Color.magenta, Color.green };
public static Color badColor = Color.red;
private AttributeSet[] matchAttrSet;
private AttributeSet badAttrSet;
public ParenMatcher() {
// create an array of AttributeSets from the array of Colors
StyleContext sc = StyleContext.getDefaultStyleContext();
badAttrSet = sc.addAttribute(SimpleAttributeSet.EMPTY,
StyleConstants.Foreground, badColor);
matchAttrSet = new AttributeSet[matchColor.length];
for (int j = 0; j < matchColor.length; j += 1)
matchAttrSet[j] = sc.addAttribute(SimpleAttributeSet.EMPTY,
StyleConstants.Foreground, matchColor[j]);
}
// match and color the parens/brackets/braces
public void run() {
StyledDocument doc = getStyledDocument();
String text = "";
int len = doc.getLength();
try {
text = doc.getText(0, len);
} catch (BadLocationException ble) {
}
java.util.Stack stack = new java.util.Stack();
for (int j = 0; j < text.length(); j += 1) {
char ch = text.charAt(j);
if (ch == '(' || ch == '[' || ch == '{') {
int depth = stack.size();
stack.push("" + ch + j); // push a String containg the char and
// the offset
AttributeSet aset = matchAttrSet[depth % matchAttrSet.length];
doc.setCharacterAttributes(j, 1, aset, false);
}
if (ch == ')' || ch == ']' || ch == '}') {
String peek = stack.empty() ? "." : (String) stack.peek();
if (matches(peek.charAt(0), ch)) { // does it match?
stack.pop();
int depth = stack.size();
AttributeSet aset = matchAttrSet[depth
% matchAttrSet.length];
doc.setCharacterAttributes(j, 1, aset, false);
} else { // mismatch
doc.setCharacterAttributes(j, 1, badAttrSet, false);
}
}
}
while (!stack.empty()) { // anything left in the stack is a mismatch
String pop = (String) stack.pop();
int offset = Integer.parseInt(pop.substring(1));
doc.setCharacterAttributes(offset, 1, badAttrSet, false);
}
}
// unset the foreground color (if any) whenever the user enters text
// (if not for this, text entered after a paren would catch the paren's
// color)
public void replaceSelection(String content) {
getInputAttributes().removeAttribute(StyleConstants.Foreground);
super.replaceSelection(content);
}
// return true if 'left' and 'right' are matching parens/brackets/braces
public static boolean matches(char left, char right) {
if (left == '(')
return (right == ')');
if (left == '[')
return (right == ']');
if (left == '{')
return (right == '}');
return false;
}
public static void main(String[] args) {
JFrame frame = new JFrame("ParenMatcher");
final ParenMatcher matcher = new ParenMatcher();
matcher.setText("int fact(int n) {\n" + " if (n <= 1) return 1;\n"
+ " return(n * fact(n-1));\n" + "}\n");
frame.getContentPane().add(new JScrollPane(matcher),
BorderLayout.CENTER);
JButton matchButton = new JButton("match parens");
matchButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent ae) {
matcher.run();
}
});
frame.getContentPane().add(matchButton, BorderLayout.SOUTH);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(200, 150);
frame.setVisible(true);
}
}
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