1. Method

1.1 Overview

Method s in Java may also be called Function s in other languages.For some complex code logic, if you want to reuse the code and use it "anytime, anywhere", you can put it in a brace "{}" and give it a name.When using code, simply find the name call.

Form 1.2

First, learn about two concepts about methods:
1. Parameter: refers to the data that enters the method, with which the method can execute logic.
2. Return value: refers to the data that comes out of the method, that is, the final result data after the method is executed
The basic format of the methods currently defined:

The name of the method's modifier method's return value method (parameter list) {code/method body}

1.3 Exercise 1: Method Calls

package cn.qile.method;

//Use of test methods
public class Test1_Method {

    public static void main(String[] args) {
        System.out.println(1);
        method();//1. Calls between methods
        System.out.println(2);
    }

    //Create method()
    //The name of the method's modifier method's return value method (parameter list) {code/method body}
    public static void method() {
        System.out.println(3);
        System.out.println(4);
        System.out.println(5);
    }

}

Run result:

1
3
4
5
2

1.4 Exercise 2: Method Passage

package cn.qile.method;

//Use of test methods
public class Test1_Method {
    public static void main(String[] args) {
//     System.out.println(1);
//     method();//1, call between methods
//     System.out.println(2);
        
        method2(10);//2. Pass-through between methods, parameter passed when calling--argument
        method3("10",5);//2.1. Pass multiple parameters separated by commas
    }
    
    
    //TODO creates method3("jack",5) parameter type parameter name - - parameter
    //Where the parameter type must be the same as the parameter type when invoked
    public static void method3(String n,int a) {
        
        //+is a concatenation of strings, and between two numbers+is used for addition
        //Use + is a stitched string whenever there is a string type
        System.out.println(n+a);//105
    }
    
    //TODO Create method2(10)
    //The name of the method's modifier method's return value method (parameter type parameter name) {code/method body}
    public static void method2(int number) {
        System.out.println(number);
    }
    
    //Create method()
    //The name of the method's modifier method's return value method (parameter list) {code/method body}
    public static void method() {
        System.out.println(3);
        System.out.println(4);
        System.out.println(5);
    }
    
}

Run result:

10
105

1.5 Exercise 3: Return values

package cn.qile.method;

//Use of test methods
public class Test1_Method {

        public static void main(String[] args) {
////       System.out.println(1);
//// method();//1, call between methods
////       System.out.println(2);
//
//     method2(10);//2, passing between methods, parameter passed when calling - argument
//     Method3 ("10, 5);//2.1, pass multiple parameters, comma separated

            int result = method4(10,5);//3. Return Value of Method
            System.out.println(result);
        }
        //TODO method4(10,5)
        public static int method4(int a,int b) {
            //Return keyword, you can return the result of the operation, call the location
            return a+b;
        }


        //TODO creates method3("jack",5) parameter type parameter name - - parameter
        //Where the parameter type must be the same as the parameter type when invoked
        public static void method3(String n,int a) {

            //+is a concatenation of strings, and between two numbers+is used for addition
            //Use + is a stitched string whenever there is a string type
            System.out.println(n+a);//105
        }

        //TODO Create method2(10)
        //The name of the method's modifier method's return value method (parameter type parameter name) {code/method body}
        public static void method2(int number) {
            System.out.println(number);
        }

        //Create method()
        //The name of the method's modifier method's return value method (parameter list) {code/method body}
        public static void method() {
            System.out.println(3);
            System.out.println(4);
            System.out.println(5);
        }

}

Run result: 15

2. Method overload

2.1 Concepts

Method overload refers to defining multiple methods with the same name in a class.
However, each method is required to have a different parameter list (that is, the number and type of parameters are different).
When a program calls a method, it can decide which method to use by passing different numbers and types of parameters to them.

2.2 Exercise: Sum of Numbers

package cn.qile.method;

//Test method overload
//Meaning of overloading: If more than one method with the same name is provided, the difference is the parameter list.
//The purpose is to facilitate external calls and reflect the flexibility of the program
public class Test2_Overload {

    public static void main(String[] args) {
        //Overload: Method names are the same + parameter lists are different (number or type of parameters are different)
        int sum = method(10,5);
        System.out.println(sum);

        String sum2 = method("jack",10,5);
        System.out.println(sum2);

        String sum3 = method(10,5,"jack");
        System.out.println(sum3);
    }

    //Create method(10,5,"jack")
    public static String method(int a,int b,String c) {
        return a+b+c;//15jack
    }

    //Create method("jack",10,5)
    public static String method(String n,int o,int p){
        return n+o+p;//jack105
    }

    //Create method(10,5) -- where 10 and 5 are arguments and a and b are formal parameters
    public static int method(int a,int b) {
        return a+b;
    }

}

Run result:

15
jack105
15jack

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