Introduction to java (6) | Definition and use of methods
Start from scratch!!!
In the previous period, we explained and practiced the branch structure of java, such as if, if (judgment statement..){Code that meets the criteria...}else{unsatisfactory code}, else if, and switch case, how do you understand them?
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This is an introduction to the method method, which is also called a function. Its basic format is:
The name of the method's modifier method's return value method (parameter list) {code/method body}
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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