Java this keyword

Usage of Java this keyword

There are 6 uses of this keyword in java

• ‘this’ keyword can be used to refer current class instance variables
• ‘this’ keyword can be used to current class constructor
• ‘this’ keyword can be used to return the current class instance
• ‘this’ keyword can be used as method parameter
• ‘this’ keyword can be used to invoke current class method
• ‘this’ keyword can be used as an argument in the constructor call

1.this-keyword-can-be-used-to-refer-current-class-instance-variables

The keyword this can be used to refer to the current class instance variable. If there is any discrepancy between the instance variables and arguments, this keyword resolves it.

Java program or using 'this' keyword to refer current class instance variables

 // Java program or using 'this' keyword to refer current class instance variables  

class StaticTest
{
    int x;
    int y; 
    StaticTest(int x, int y)
    {
        this.x = x;
        this.y = y;
    }
    void display()
    {
        System.out.println("x : " + x + "  y : " + y +"\n\nX+Y="+(x+y));
    }
 
    public static void main(String[] args)
    {
    	StaticTest object = new StaticTest(5, 5);
        object.display();
    }
}

x : 5  y : 5 

 
 X+Y=10 

2.‘this’ keyword can be used to invoke current class constructor

To invoke the current class constructor, use the this() constructor call. It allows you to reuse the constructor. In other words, it is used to link constructors.

Java program using 'this' keyword used to invoke current class constructor

 // Java program  using 'this' keyword used to invoke current class constructor  

class StaticTest
{
    int x;
    int y; 
    public StaticTest() {
		// TODO Auto-generated constructor stub
    	this(10, 10);
    }
    StaticTest(int x, int y)
    {
        this.x = x;
        this.y = y;
    }
    void display()
    {
        System.out.println("x : " + x + "  y : " + y +"\n\nX+Y="+(x+y));
    }
 
    public static void main(String[] args)
    {
    	StaticTest object = new StaticTest(); // here no need to here give value 
        object.display();
    }
}

x : 10  y : 10 

 
 X+Y=20 

3.‘this’ keyword can be used to return the current class instance

To invoke the current class constructor, use the this() constructor call. It allows you to reuse the constructor. In other words, it is used to link constructors.

Java program using 'this' keyword used to invoke current class instance

 // Java program  using 'this' keyword used to invoke current class instance  

class StaticTest
{
    int x;
    int y;
    StaticTest(int x, int y)
    {
        this.x = x;
        this.y = y;
    }
    StaticTest get()
    {
        return this;
    }
    void display()
    {
        System.out.println("x : " + x + "  y : " + y +"\n\nX+Y="+(x+y));
    }
 
    public static void main(String[] args)
    {
    	StaticTest object = new StaticTest(10, 10); // here no need to here give value 
    	object.get().display();
    }
}

x : 10  y : 10 

 
 X+Y=20 

4.‘this’ keyword can be used as method parameter

The keyword this can also be used as an argument in a method. It is primarily used in event handling.

Java program using ‘this’ keyword as method parameter

 // Java program  using ‘this’ keyword  as  method parameter  

class StaticTest
{
    int x;
    int y;
    StaticTest(int x, int y)
    {
        this.x = x;
        this.y = y;
    }
    void display(StaticTest test)
    {
        System.out.println("x : " +test.x + "  y : " + test.y);
    }
   
    void p() // this method return current class instance
    {
        display(this);
    }
 
    public static void main(String[] args)
    {
    	StaticTest object = new StaticTest(10, 10); // here no need to here give value 
    	object.p();
    }
}

x : 10  y : 10 

5.‘this’ keyword can be used as an argument in the constructor call

To invoke the current class constructor, use the this() constructor call. It allows you to reuse the constructor. In other words, it is used to link constructors.

Java program using ‘this’ keyword as method parameter

 // Java program  using ‘this’ keyword  as  method parameter  

class StaticCheck{  
  StaticTest obj;  
  StaticCheck(StaticTest obj){  
      this.obj=obj;  
    }  
    void display(){  
     System.out.println(obj.x); 
    }  
}

class StaticTest{  
  String x="Alok";  
  StaticTest(){  
  StaticCheck staticCheck=new StaticCheck(this);  
  staticCheck.display();  
  }  
  public static void main(String args[]){  
	  StaticTest object=new StaticTest();  
  }  
} 

Alok 

6.‘this’ keyword can be used to invoke current class method

Java program using ‘this’ keyword to invoke current class method

 // Java program  using ‘this’ keyword to  invoke current class method  

class StaticTest{  
    String x="Alok";  
  void display()
  {    
      this.show(); // this code will call  show() method
      System.out.println(x);
  }   
  void show() {
      System.out.println("I am Show method");
  } 
  public static void main(String args[]){  
	  StaticTest object=new StaticTest(); 
	  object.display();
  }  
}

I am Show method 

Alok