this vs super

Java provide keyword this and and super

1. this keyword
   • refer to current object reference
   • use to un-hide instance variable from local variable
   • this() use to invoke current constructor
2. Super keyword
   1. refer to parent (super class) object reference
   2. use to call (invoke ) accessible data member and  member  method of super class.
   3. super() : use to invoke super class constructor

 

Example :

public class Person {

	private String fname;
	public String lname;
	public Person(String fname, String lname) {
		this.fname = fname;
		this.lname = lname;
	}
	public String getFname() {
		return fname;
	}
	public void setFname(String fname) {
		this.fname = fname;
	}
	@Override
	public String toString() {
		return "fname=" + this.fname + ", lname=" + this.lname ;
	}
	
	
	
}

public class Student extends Person {
	private double salary;
	public Student(String fname, String lname) {
		super(fname, lname);// call super class constructor 
		System.out.println("this sub class Constructor ");
	}
	public Student(String fname, String lname, double salary) {
		super(fname, lname);// call super class constructor
		this.salary = salary;
	}
	@Override
	public String toString() {
		// super.toString() invoke super class method
		return super.toString()+"salary=" + this.salary ;
	}

	public void disPlay() {
		System.out.println("First name :"+this.getFname()+"Last name: "+
				super.lname+"salary=" + salary);
		
//		or 
//		invoke super class toString method
		System.out.println(super.toString()+ " salary= " + salary);
//		or
//	 keyword this can be delete => toString()
		System.out.println(this.toString());
	}
	
	
	
}

public class Test {

	public static void main(String[] args) {
		Student st = new Student("Learning","Tonight",100);
		System.out.println(st.toString());
		st.disPlay();

	}

}

Output:

fname=Learning, lname=Tonightsalary=100.0
First name :LearningLast name: Tonightsalary=100.0
fname=Learning, lname=Tonight salary= 100.0
fname=Learning, lname=Tonightsalary=100.0