在匿名内部类中只有final变量是可访问的的原因

1private void f(Button b, final int a){
2    b.addClickHandler(new ClickHandler() {
3        @Override
4        public void onClick(ClickEvent event) {
5            int b = a*5;
6        }
7    });
8}

 1class Example {
 2    private int a;
 3
 4    private void f(Button b, int a) {
 5        this.a = a;
 6
 7        b.addClickHandler(new ClickHandler() {
 8            @Override
 9            public void onClick(ClickEvent event) {
10                int b = Example.this.a * 5;
11            }
12        });
13    }
14}