Overloading and rewriting

heavy load

Overloading is in a class , The method name is the same , And the parameters are different . The return type can be the same or different .

In a program , If you want to use the same method , And when using methods , Different data types are used , Or the number of data 、 Different order , Method overloading can be used .

rewrite

Rewriting requires inheritance , Same method name , Parameters are the same , Overrides the method of the parent class .

Method rewriting needs to meet ：

1. Methods in the parent class and methods in the subclass
2. Method names must be consistent
3. Method parameters must be consistent
4. Access modifiers of subclass methods cannot narrow access permissions
5. The return value type should be consistent

There is an animal , There is a way of sleeping in animals , Cats and dogs also have ways to sleep

public class Animal {
    public void sleep(){
        System.out.println(" Animals sleep ");
    }
}

  Create a dog class , It also has a way to sleep

public class Dog extends Animal{
    @Override
    public void sleep() {
        System.out.println(" Dogs sleep ");
    }
}

Create a cat class , It also has a way to sleep

public class Cat extends Animal{
    @Override
    public void sleep() {
        System.out.println(" Cats sleep ");
    }
}

Create a Test Class test

public class Test03 {
    public static void main(String[] args) {
        Dog dog = new Dog();
        dog.sleep();
        Cat cat = new Cat();
        cat.sleep();
    }
}

result ：

  summary ：

The overridden method parameter list must be the same , The overloaded method parameter list must be different , The return value type of the overridden method can only be the parent type or the subclass of the parent type , Overloaded methods do not require the return value type .