Explain the java this keyword.

This definition:

Java’s ‘this’ keyword is used to refer the current instance of the method on which it is used.

Following are the ways to use this

1) To specifically denote that the instance variable is used instead of static or local varible.That is,

private String javaFAQ;
void methodName(String javaFAQ) {
this.javaFAQ = javaFAQ;
}

Here this refers to the instance variable. Here the precedence is high for the local variable. Therefore the absense of the this denotes the local variable. If the local variable that is parameter’s name is not same as instance variable then irrespective of this is used or not it denotes the instance variable.

2) This is used to refer the constructors

public JavaQuestions(String javapapers) {
this(javapapers, true);
}

This invokes the constructor of the same java class which has two parameters.

3) This is used to pass the current java instance as parameter

obj.itIsMe(this);

4) Similar to the above this can also be used to return the current instance

CurrentClassName startMethod() {
return this;
}

Note: This may lead to undesired results while used in inner classes in the above two points. Since this will refer to the inner class and not the outer instance.

5) This can be used to get the handle of the current class

Class className = this.getClass(); // this methodology is preferable in java

Though this can be done by, Class className = ABC.class; // here ABC refers to the class name and you need to know that!

As always, this is associated with its instance and this will not work in static methods.

How is this?