What is the purpose of anonymous inner classes in Java?

Anonymous inner class is a special inner class used to implement the callback mechanism and provide customized behavior for other code. They achieve their functions by overriding non-abstract methods of external classes, including event handling, callback mechanisms and dynamic behavior. In practice, anonymous inner classes can be used to implement button click event handlers and callback functions.

The role of anonymous inner classes in Java

Anonymous inner classes is a special inner class in Java that has no clear class name, but directly implemented as an inner class of its outer class. Anonymous inner classes are mainly used to implement callback mechanisms and provide customized behavior for other code.

Create anonymous inner classes

Anonymous inner classes can be created through the following syntax:

new OuterClass() {
    // 匿名内部类的实现
}

For example:

// 创建一个按钮，当按下时打印"Hello World"
JButton button = new JButton() {
    @Override
    public void actionPerformed(ActionEvent e) {
        System.out.println("Hello World!");
    }
};

Function

Anonymous inner classes Classes can achieve the following functions by overriding non-abstract methods of external classes:

• Event processing: Anonymous inner classes are often used for event processing, such as mouse click events and keyboard input events. wait.
• Callback mechanism: Anonymous inner classes can provide callback functions for other codes to achieve customized processing.
• Dynamic behavior: Anonymous inner classes can dynamically modify the behavior of outer classes according to specific scenarios.

Practical Case

Case 1: Event Handling

Use an anonymous inner class to implement a button click event handler:

// 创建一个按钮
JButton button = new JButton("Click Me");

// 为按钮添加点击事件处理器
button.addActionListener(new ActionListener() {
    @Override
    public void actionPerformed(ActionEvent e) {
        System.out.println("Button clicked!");
    }
});

Case 2: Callback mechanism

Define an interface to define a callback method that needs to be implemented:

interface MyCallback {
    void callback(String message);
}

Use an anonymous inner class to implement the callback method:

MyCallback callback = new MyCallback() {
    @Override
    public void callback(String message) {
        System.out.println("Callback received: " + message);
    }
};

Then you can call the callback method where needed:

callback.callback("Hello from callback!");

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