When to use "this" keyword in Java?

"this" keyword plays an important role in Java to reduce the number of lines code and performance. You can observe the following important uses of "this" keyword.

• To refer current class instance variables.
• To invoke current class method.
• To invoke current class constructor.
• To return the current class instance.

Example 1: 

class Employee{
int employeeId;
String employeeName;

Employee(int employeeId,String employeeName){
this.employeeId= employeeId;
this.employeeName= employeeName;
}
void display(){
      System.out.println(employeeId+" "+employeeName);
}
public static void main(String args[]){
               Employee e1 = new Employee (111,"John");
               Employee e2 = new Employee (222,"Abraham");
               e1.display();
               e2.display();
    }
}

Example 2: 

class Employee{
int employeeId;
String employeeName;
String company;

Employee(int employeeId,String employeeName){
         this.employeeId= employeeId;
         this.employeeName= employeeName;
}

Employee(int employeeId,String employeeName, String company){
         this(employeeId, employeeName);   // No need to initialize employeeId, employeeName
         this.company = company;
}


void display(){

      System.out.println(employeeId+" "+employeeName);
}
public static void main(String args[]){
          Employee e1 = new Employee (111,"John");
          Employee e2 = new Employee (222,"Abraham");
           e1.display();
           e2.display();
   }
}

• Can be passed as an argument in method

class A{
         void m(A obj){
         System.out.println("method is invoked");
   }

void p(){
            m(this);
            }

public static void main(String args[]){
A a1 = new A();
a1.p();
  }
}

• To return as statement from the method

class B{
B getB(){
return this;
} 

 
void msg(){

    System.out.println("Hello World");

   }
}

class Test{
public static void main(String args[]){
new B().getB().msg();
}
}