Method overloading and method rewriting

Catalog

One 、 Method overloading

Two 、 Method rewriting （ Methods cover ）

3、 ... and 、 Comparison between method overloading and method rewriting

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One 、 Method overloading

Java Allow a class , Multiple methods with the same name exist , But the formal parameter list is required to be inconsistent. Multiple methods with the same name exist , But the required formal parameter list is inconsistent （ Method name must be the same , The formal parameter list must be different （ Number of formal parameters 、 Or type 、 Or in different order ）, There is no requirement for return type ）

Code example ：m Method overloading

class Methods{
	public int m(int n){
		return n*n;
	}
	public int m(int n,int a){
		return n*a;
	}
	public String m(String c){
		return c;
	}
}

Two 、 Method rewriting （ Methods cover ）

Method rewriting （ Cover ） The subclass has a method , And the name of a method of the parent class 、 Return type 、 Same parameter , Then we will say that the methods of this subclass cover the methods of the parent class .

Method rewriting needs to meet the following conditions ：

（1） Parameters of subclass methods 、 The method name should be exactly the same as that of the parent class

（2） The return type of the subclass method is the same as that of the parent class , Or a subclass of the return type of the parent class

（3） A subclass method cannot reduce the access rights of a parent method

Code example ：

Both parent and child classes have say Method is the rewriting of method （set and get Method is to operate on private attributes ）

// Parent class person
public class Person {

        private int age;

    public Person( int age) {   
            this.age = age;
        }
        public String say(){
            System.out.println("Person Self introduction. :");
            return " age="+age;
    }
// Subclass student
public class Student extends Person{
    private String id;

    public Student(int age, String id) {
        super(age);
        this.id = id;
    }
    public String say(){
        System.out.println("Student Self introduction. ：");
        return super.say()+"id="+id;
    }
}

3、 ... and 、 Comparison between method overloading and method rewriting

name	Range of occurrence	Method name	Return type	Parameter list	Modifier
heavy load	In this category	It has to be the same	No requirements	type 、 At least one difference in order or number	No requirements
rewrite	Parents and children	It has to be the same	The return type of the subclass method is the same as that of the parent class , Or a subclass of the return type of the parent class	identical	Subclass methods cannot narrow the access scope of parent methods