this: to refer current class instance variable

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The this keyword can be used to refer current class instance variable. If there is ambiguity between the instance variables and parameters, this keyword resolves the problem of ambiguity.

Understanding the problem without this keyword

    class Student{  
    int rollno;  
    String name;  
    float fee;  
    Student(int rollno,String name,float fee){  
    rollno=rollno;  
    name=name;  
    fee=fee;  
    }  
    void display(){System.out.println(rollno+" "+name+" "+fee);}  
    }  
    class TestThis1{  
    public static void main(String args[]){  
    Student s1=new Student(111,"ankit",5000f);  
    Student s2=new Student(112,"sumit",6000f);  
    s1.display();  
    s2.display();  
    }
}  

Output

0 null 0.0
0 null 0.0

Solution of the above problem by this keyword

    class Student{  
    int rollno;  
    String name;  
    float fee;  
    Student(int rollno,String name,float fee){  
    this.rollno=rollno;  
    this.name=name;  
    this.fee=fee;  
    }  
    void display(){System.out.println(rollno+" "+name+" "+fee);}  
    }  
      
    class TestThis2{  
    public static void main(String args[]){  
    Student s1=new Student(111,"ankit",5000f);  
    Student s2=new Student(112,"sumit",6000f);  
    s1.display();  
    s2.display();  
    }}  

Output

111 ankit 5000
112 sumit 6000

Program where this keyword is not required

    class Student{  
    int rollno;  
    String name;  
    float fee;  
    Student(int r,String n,float f){  
    rollno=r;  
    name=n;  
    fee=f;  
    }  
    void display(){System.out.println(rollno+" "+name+" "+fee);}  
    }  
      
    class TestThis3{  
    public static void main(String args[]){  
    Student s1=new Student(111,"ankit",5000f);  
    Student s2=new Student(112,"sumit",6000f);  
    s1.display();  
    s2.display();  
    }}  

Output

111 ankit 5000
112 sumit 6000

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