A program lets you understand what static inner classes, local inner classes, and anonymous inner classes are

An inner class is a class defined in another class . Why use inner classes ？ The main reasons are as follows ：

• Internal class methods can access the data in the scope where the class definition is located , Include private The data of .
• Inner classes can be hidden from other classes in the same package .
• When you want to define a callback function and don't want to write a lot of code , It is convenient to use anonymous inner class .

Next, let's take the code as an example

public class Test {
//     Static inner class 
static class C implements A {
    @Override
    public void lambad() {
        System.out.println(" I'm a static inner class ");
    }
}

    public static void main(String[] args) {
        A object = new B();
        object.lambad();
//         Static inner class way 
        object = new C();
        object.lambad();

//         Local inner classes 
        class D implements A {
            @Override
            public void lambad() {
                System.out.println(" I'm a local inner class ");
            }
        }
        object = new D();
        object.lambad();

//         Anonymous inner class   There is no class name , Must implement the interface or parent class 
        object = new A() {
            @Override
            public void lambad() {
                System.out.println(" I'm an anonymous inner class ");
            }
        };
        object.lambad();
    }
}
// Define a functional interface 
interface A {
    void lambad();
}
// Implementation class 
class B implements A {

    @Override
    public void lambad() {
        System.out.println(" I am a general implementation class ");
    }
}

 

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