What is the mechanism by which Java implements polymorphism?-JavaBase-php.cn

What is the mechanism by which Java implements polymorphism?

Guanhui

Release： 2020-06-01 11:00:04

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What is the mechanism by which Java implements polymorphism?

What is the implementation mechanism of polymorphism in Java

The mechanism to implement polymorphism in Java relies on references from parent classes or interfaces to point to subclasses , thereby realizing the characteristics of multiple forms of an object. The reference of its parent class dynamically points to the specific instance at runtime. When the method of the reference is called, it does not run according to the method defined in the type of the reference variable, but according to the method defined in the type of the reference variable. Concrete instance methods.

Simple example

Person.java

import java.util.Scanner;

public class Person {
    public int salary;
    public int allSalary(){
        return 0;
    }
    public static void main(String[] args) {
        Person p = null;

        for (int n = 0; n < 3; n++) {
            @SuppressWarnings("resource")
            Scanner sc = new Scanner(System.in);
            System.out.println("请输入一个1-3的数字：\n1 is Teacher\n2 is Scientis\n3 is Waiter");
            int i = sc.nextInt();
            //分别指向了不同的子类，输出的结果是不一样的
            if (i == 1) {
                p = new Teacher(5000);
                System.out.println(p.allSalary());
            } else if (i == 2) {
                p = new Scientist(5000);
                System.out.println(p.allSalary());
            } else if (i == 3) {
                p = new Waiter(5000);
                System.out.println(p.allSalary());
            } else {
                System.out.println("?\n请输入1-3");
            }

        }
}
}

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Scientist .java

 public class Scientist extends Person{
    public Scientist(int salary){
        this.salary = salary;
    }

    public int allSalary(){
        int aa = salary*12+36500;
        System.out.print("五五开一年的工资：");
        return aa;
    }
}

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Waiter.java

public class Waiter extends Person{
    public Waiter(int salary){
        this.salary = salary;
    }

    public int allSalary(){
        int aa = salary*12;
        System.out.print("服务员一年的工资：");
        return aa;
    }
}

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Teacher .java

public class Teacher extends Person{
    public Teacher(int salary){
        this.salary = salary;
    }

    public int allSalary(){
        int aa = salary*12+3650;
        System.out.print("教师一年的工资：");
        return aa;
    }
}

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