How to use forced inheritance proxy final class to achieve code reuse in Java programming?

How to use forced inheritance proxy final class to achieve code reuse in Java programming?

In Java, the final keyword is used to modify classes, methods, and variables to indicate that they cannot be changed. When we face a class that is final modified, we cannot inherit it directly, but sometimes we need to add new functions to the class or modify existing functions. At this time, we can use forced inheritance proxy (final class) to achieve code reuse.

Forced inheritance proxy is a design pattern that inherits and extends the functions of the original class in the proxy class by creating a proxy class with the same interface as the original class. The following is an example of using a forced inheritance proxy to achieve code reuse:

// 被final修饰的原始类
final class FinalClass {
    void doSomething() {
        System.out.println("原始类中的方法");
    }
}

// 强制继承代理类
class ProxyClass extends FinalClass {
    private FinalClass finalClass;

    ProxyClass(FinalClass finalClass) {
        this.finalClass = finalClass;
    }

    // 继承原始类的方法，并在其中添加新功能
    @Override
    void doSomething() {
        // 调用原始类中的方法
        finalClass.doSomething();
        // 添加新功能
        System.out.println("代理类中的方法");
    }
}

// 测试类
public class Main {
    public static void main(String[] args) {
        FinalClass finalClass = new FinalClass();
        ProxyClass proxyClass = new ProxyClass(finalClass);
        proxyClass.doSomething();
    }
}

In the above example, FinalClass is a final-modified class and cannot be directly inherited. In order to achieve code reuse, we created a ProxyClass proxy class, which inherits from FinalClass. Construct a ProxyClass object by passing in the FinalClass object to implement the extension of FinalClass.

In ProxyClass, we rewrote the doSomething() method in FinalClass. In the method, we first called the doSomething() method of FinalClass, and then added a new function output. In this way, we extend the functionality of FinalClass without changing it.

In the test class Main, we created the FinalClass object and the ProxyClass object, and executed the code by calling the doSomething() method of proxyClass. In this way, through forced inheritance of the proxy (final class), we successfully achieved code reuse of the final class and added new functions at the same time.

It should be noted that when using forced inheritance proxy (final class) to achieve code reuse, you must ensure that the proxy class will not be modified, otherwise the proxy class may not work correctly. In addition, the name of the proxy class should be clear and unambiguous to indicate that it is inherited (final class).

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