Detailed explanation of the principles and usage of the adapter pattern in Java classic design patterns

This article mainly introduces the adapter pattern of Java's classic design pattern, briefly explains the concept and principle of the adapter pattern, and analyzes the usage and related precautions of the java adapter pattern in the form of examples. Friends in need can refer to it

The example in this article describes the adapter pattern of Java's classic design pattern. Share it with everyone for your reference, the details are as follows:

Adapter pattern is to adapt the interface of a class to what the user expects, so that some classes that cannot work together due to incompatible interfaces Classes work together to achieve the functionality expected by users.

Advantages of the adapter mode:

1. Through the adapter, the client can call a unified interface, the operation is simple and direct, and the code logic is compact, Easy to use.
2. Code reuse, the adapter mode solves the problem of different environmental requirements and achieves code reuse through adaptation.
3. Decouple the target class and the adapter class, and reuse the current class by creating a new adapter class. There is no need to repeatedly modify the original code to implement the opening and closing principle.

There are two types of adapter patterns

1. Object adapter pattern: In this adapter pattern, the adapter holds an object of the class it wraps. Example. In this case, the adapter calls the physics entity of the wrapped object.
2. Class adapter mode: In this adapter mode, the adapter inherits from the implemented class (generally multiple inheritance).

Sample code:

##

/**
* @description：
* 原有的接口功能，比如是给电动车充电功能
*/
public interface FirstBaseIf {
void charging();//充电
}
/**
* 要实现的操作功能
* @description：
*/
public class NewFunction {
public void powerWithTwo(){
System.out.println(“新功能：给电动汽车也可以充电啦”);
}
}
/**
*新建适配器类，来实现对原有接口FirstBaseIf的操作使用
* @description：
*/
public class FunctionAdapter implements FirstBaseIf {
private NewFunction plug;
public FunctionAdapter(NewFunction plug){
this.plug=plug;
}
@Override
public void charging() {//重写原有接口中的方法，从而实现接口转化
System.out.println(“通过适配器转化”);
plug.powerWithTwo();
}
}
//——–测试代码——————-
public class Test {
private FirstBaseIf plug;
public Test(FirstBaseIf plug) {
  this.plug = plug;
}
public static void main(String[] args) {
  NewFunction two = new NewFunction();
  FirstBaseIf three = new FunctionAdapter(two);//这里就是通过适配器实现转换
  Test note = new Test(three);
  note.charge();
}
public void charge() {
  plug.charging();//使用原有接口中的功能
}
}

Run result:

Applicable scenarios:

In a Java program, if there is an abstract class or interface, all abstract methods must be rewritten.

So, if there are too many abstract methods defined in an interface, and many abstract methods in the subclass are not needed, you should design an adapter. In Android development through the Java language, the adapter pattern is often used.

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