Working with “this” keyword:-
This keyword in java is a keyword which always refers to a current class object.T he difference between ‘new’ and ‘this’ is new is responsible to call a constructor and create a new object. Whereas “this” is responsible to call the constructor without allocating memory. this keyword can be very useful in the handling of Variable Hiding.
By the use of this keyword, a programmer can refer to any member of the current object within an instance method or a constructor.
this can be used by itself to simply refer to member variables and methods
The following are the uses of “this” keyword in Java:-
Uses-1
To call a constructor from another constructor within a single class without allocating new memory, we can use this keyword .” this” should be the first statement in a constructor.
Example
class Demo
{
Demo()
{
System.out.println("i am in demo");
}
}
class Test extends Demo
{
Test()
{
this(123);
System.out.println("i am in default");
}
Test(String x)
{
this();
System.out.println("i am in string");
}
Test(int x)
{
this(12.3);
System.out.println("i am in integer ");
}
Test(double x)
{
System.out.println("i am in double");
}
public static void main(String[] args)
{
new Test("hello");
}
}
Output
i am in demo
i am in double
i am in integer
i am in default
i am in string
Uses-2
When the local and instance variable name is the same, ‘this’ keyword is used to create a difference between them.
Example
class Test
{
int x=20;
void show()
{
int x=10;
System.out.println(x);
System.out.println(this.x);
}
public static void main(String[] args)
{
new Test().show();
}
}
Output
10
20
Uses-3
This keyword can be passed as an argument within the constructor.
Example
class Demo
{
int x=10;
Demo( Test t)
{
int x=30;
System.out.println(x);
System.out.println(this.x);
System.out.println(t.x);
}
}
class Test
{
int x=20;
void display()
{
new Demo(this);
}
public static void main(String[] args)
{
new Test().display();
}
}
Output
30
10
20
Uses-4
‘this’ keyword is used to display the current class object hash code.
Example
class Test
{
int a=10;
void show()
{
System.out.println(this);
}
public static void main(String[] args)
{
new Test().show();
}
}
Output
[email protected]
Uses-5
“this” keyword can be used as a return value.
Example
class Demo
{
int x=10;
void display(Test obj,int x)
{
System.out.println(x);
System.out.println(this.x);
System.out.println(obj.x);
}
}
class Test
{
int x=20;
void show()
{
int x=40;
new Demo().display(this,this.x);
}
public static void main(String[] args)
{
new Test().show();
}
}
Uses-6
“this” keyword can be passed as an argument within a method.
Example
class Test
{
int x=20;
void show()
{
int x=40;
new Demo().display(this,this.x);
}
public static void main(String[] args)
{
new Test().show();
}
}