This :

This is a keyword in java.

This keyword is used to refer current clas attribute

This apply on:
1)data type
2)Method
3)constructor

Why this is used in JAVA?

		  
class student{
    int id;
    String name;
			 
	student(int id,String name){
	    id=id;
	    name=name;
	}
				  
	void show(){
	    System.out.println(id+" "+name);
	}   
	   
	public static void main(String args[]){
       student s=new student(123,"max");
	   s.show();
   }
}
          

OUTPUT:
O NULL
          

Observation :

As we observe that compiled achieve ambigious condition as it got confuse about which one is class id and which one is
method id.So result is 0 for int data types ans null for String data types

Solution :

To overcome above problem ,java used this in program to differentiate class attribute and method attribute.

class student{
	int id;
	String name;
			 
	student(int id,String name){
	  this.id=id;     // this differentiate between class attribute and method attribute
      this.name=name; // this differentiate between class attribute and method attribute
	}		  
	void show(){
	  System.out.println(id+" "+name);
	}  
			   
	public static void main(String args[]){
	    student s=new student(123,"max");
	    s.show();
	}
}
          

OUTPUT: 
123 max
          

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