在Java中匿名类有什么用?我们可以说使用匿名类是Java的优点之一吗?

a can only be final here. Why? How can I reassign a in onClick() method without keeping it as private member? private void f(Button b, final int a){ b.addClickHandler(new ClickHandler() { @Override public void onClick(ClickEvent event) { int b = a*5; } }); } How can I return the 5 * a when it clicked? I mean, private void f(Button b, final int a){ b.addClickHandler(new ClickHandler() { @Override public void onClick(ClickEvent event) { int b = a*5; return b; // but return type is void } }); }