[Easy-to-understand explanation! ] How to use Java overload

1. Prior knowledge

-[Latest] How to build Java environment on Ubuntu

-[Even beginners can do it! ] How to create a Java environment on Windows 10 (JDK14.0.1)

-[Easy-to-understand explanation! ] How to use Java instance

-[Even beginners can do it! ] How to install Eclipse on Windows 10 (Java environment construction)

As prior knowledge, the contents of the above link are required.

2. What is overload?

--Overload means defining a method with the same method name but with number of different arguments or different argument types. --If there are multiple constructors with the same number of arguments, theconstructors with the same argument type are called. --You can also call another constructor by usingthis ()from within the constructor. --The call to the constructor bythis () must be written at the beginning `of the constructor.

3. Basic writing

Test class

package package name;
public class main class name{
    public static void main(String[] args) {
        //Instance generation
Class name Variable name 1=new class name();
Class name Variable name 2=new class name(Actual argument);
Class name Variable name 3=new class name(Actual argument of a type different from variable name 2);
    }
}

Overlord class

package package name;
class class name{
    //Definition of instance variables
private type name variable name;

    //Constructor 1 (no arguments)
name of the class(){
Initialization process, etc.
    }
    //Constructor 2 (with arguments)
name of the class(Type name Argument name){
Initialization process, etc.
    }
    //Constructor 3 (with different arguments than constructor 2)
name of the class(Type name Argument name){
Initialization process, etc.
    }
}

--Basic overload is described as above.

4. Preparation

1. Start Eclipse and select [File (F)]-> [New (N)]-> [Java Project].
2. Enter Test1 for the project name and click the Done button.
3. Select [File (F)] → [New (N)] → [Class].
4. Enter Test1 for the package and name and click the Done button.
5. Confirm that Test1.java has been created. Enter Test1 in the package, enter TestOverload in the name, and click the Finish button in the same way as in 6.3.
6. Success if Test1.java and TestOverload.java are created.

5. Description example

--The advantage of using overload is that you don't have to remember multiple methods with different names. --For example, it can be used when there are people who have confirmed attendance andpeople who have not decided in advance, such asconfirmation of attendance`. (It can be completed only with the constructor without creating three methods of attendance, absence, and undecided.)

Test1.java

//Attendance confirmation system
package Test1;
public class Test1 {
    public static void main(String[] args) {
        //Instance generation
    	TestOverload to1 = new TestOverload("A");
    	TestOverload to2 = new TestOverload("B",1);
    	TestOverload to3 = new TestOverload("C",2);

    	System.out.println("-----April 1st-----");
    	//View the contents of the instance
    	to1.showAttendance();
    	to2.showAttendance();
    	to3.showAttendance();
    }
}

TestOverload.java

package Test1;
public class TestOverload {
    //Definition of instance variables
    private String name;
    private int attend;

    //Constructor 1 (no arguments)
    TestOverload(){
    	this("Not entered",0);
    }
    //Constructor 2 (with arguments)
    TestOverload(String name){
    	this(name,0);
    }
    //Constructor 3 (with different arguments than constructor 2)
    TestOverload(int attend){
    	this("Not entered",attend);
    }
    //Constructor 4 (2 arguments)
    TestOverload(String name,int attend){
    	this.name = name;
    	this.attend = attend;
    }

	//Display method
    void showAttendance(){
    	String str = "";
    	switch(attend) {
    	case 0:
    		str += "Undecided";
    		break;
    	case 1:
    		str += "Attendance";
    		break;
    	case 2:
    		str += "Absence";
    		break;
    	}
    	System.out.println(name+"Is"+str);
    }
}

--Copy the above sentence, specify S-JIS as the character code, save the file name as Test1.java, TestOverload.java, and execute it. ↓ ↓

6. Related

-[Useful to remember !!!] Easy creation of constructor and getter / setter in Eclipse -[Even beginners can do it! ] How to write Javadoc -[Easy-to-understand explanation! ] How to use Java encapsulation