java method overloading example

What is method overloading?

Method overloading is a means of handling different data types in a unified way.

How to constitute method overloading?

The method names are the same but the formal parameters are different. The difference in formal parameters is expressed in: 1). The number of formal parameters is different 2). The types of formal parameters are different 3). The order of formal parameters is different

Notes

1. If the return values ​​of the two methods are different, but everything else is the same. This does not constitute method overloading. An error will be reported during compilation:

Sample code (wrong): Test.java

/*返回值的不同并不能构成方法的重载*/
public class Test {
    public static void main(String[] args) {

    }   
}
class A { 
    public void f() {               //返回值为 void
    }  
    public int f() {                //返回值为 int, 其他和上面的f()方法是一样的
        return 1;
    }   
}

Error message:

Test.java:12: error: method f() is already defined in class A
      public int f() {
               ^
          1 error

2. 构造方法和普通方法一样， 也可以方法重载。

Sample code (correct): Test.java

/* 方法的重载
 * 输出结果:
 * public A() {} 这个构造方法被调用了
 * public A(int i) {} 这个构造方法被调用了
 * public void f() {} 这个构造方法被调用了
 * public void f(int i) {} 这个构造方法被调用了
 */
public class Test {
    public static void main(String[] args) {
        A aa1 = new A();                //调用9行那个方法
        A aa2 = new A(1);               //调用13行那个方法
        aa1.f();                        //调用17行那个方法
        aa2.f(1);                       //调用21行那个方法
    }   
}

class A { 
    public A() {                    //9行
        System.out.printf("public A() {} 这个构造方法被调用了\n");
    }  
    public A(int i) {               //13行
        System.out.printf("public A(int i) {} 这个构造方法被调用了\n");
    }  
    public void f() {               //17行
        System.out.printf("public void f() {} 这个构造方法被调用了\n");
    }  
    public void f(int i) {          //21行
        System.out.printf("public void f(int i) {} 这个构造方法被调用了\n");
    }   
}

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