Question

So, I’m trying to define a set of methods for a large set of buttons, and I figured I could do it in a for loop, but I’m getting a syntax error which I can’t decipher… Here’s a simplified version of the code I want to use… The error is: “Syntax error on token(s), misplaced construct(s)”

JMenu blocks = new JMenu("Block");
menuBar.add(blocks);

for (int i=0; i < 9; i++){
  public void action() {
      System.out.println(i+"");
  }
  JMenuItem blockName = new JMenuItem(i+"");
  blockName.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent arg0) {
          action();
      }
  });
  blocks.add(blockName);
}

Answer 1

Java methods are not first-class objects (or second or third-class objects; in fact, methods are not objects at all). You need to move the method into one of the classes – either your top class, or the anonymous inner class that you defined, like this:

for (int i=0; i < 9; i++) {
    // You cannot access i from methods of the anonymous inner class
    // because it is not final, but you can make a final copy
    final int iCopy = i;
    JMenuItem blockName = new JMenuItem(i+"");
    blockName.addActionListener(new ActionListener() {
        // It is OK to define additional methods here:
        public void action() {
            System.out.println(iCopy+"");
        }
        public void actionPerformed(ActionEvent arg0) {
            action();
        }
    });
    blocks.add(blockName);
}