Java – declare anonymous inner classes

rb.addActionListener(new ActionEvent(ae) {

rb.addActionListener(new ActionEvent(ae) {
   public void actionPerformed(ActionEvent ae) {
     NowCall(ae);
    }
});

Other ways

Thread th=new Thread(Runnable r) {
  public void run() {
    // do something
  }
};

// notice the ending of above 2 snippets

Seeing these two, I'm really confused There seems to be no exact pattern for declaring an anonymous inner class

Please explain the syntax of anonymous inner classes

Solution

The second is invalid, as far as I know and tested

More commonly, create a new runnable implementation:

Thread th=new Thread(new Runnable() {
  @Override
  public void run() {
    // This implements Runnable.run
  }
});

Now you can override the run method of ordinary threads:

Thread th=new Thread() {
  @Override
  public void run() {
    // This overrides Thread.run
  }
};

... but I personally prefer to specify runnable separately when creating threads

Now the only difference you notice at the end is whether the expression is used as a parameter (for example, for addactionlistener method or thread (runnable) constructor, or whether it is only directly assigned to a variable Think of the new typename () {...} as a single expression. It's just the difference:

Thread th = expression;

and

Thread th = new Runnable(expression);