Most asked top Interview Questions and Answers | Online Test | Mock Test
Education platform for interview prep, online tests, tutorials, and live practice

Build skills with focused learning paths, mock tests, and interview-ready content.

WithoutBook brings subject-wise interview questions, online practice tests, tutorials, and comparison guides into one responsive learning workspace.

Search the library
Prepare Interview
Ask Question

Mock Exams

Make Homepage

Bookmark this page

Subscribe Email Address

Core Java Interview Questions and Answers

Question: What is this() keyword in core java and when should we use this() in core java?
Answer:
The this keyword is primarily used in three situations. The first and most common is in setter methods to disambiguate variable references. The second is when there is a need to pass the current class instance as an argument to a method of another object. The third is as a way to call alternate constructors from within a constructor.

Example of Case 1: Using this to disambiguate variable references. In Java setter methods, we commonly pass in an argument with the same name as the private member variable we are attempting to set. We then assign the argument x to this.x.
public class Foo {
    private String name;
    // ...
    public void setName(String name) {
        // This makes it clear that you are assigning 
        // the value of the parameter "name" to the 
        // instance variable "name".
        this.name = name;
    }
    // ...
}
Example of Case 2: Using this we can pass current class object through method argument to another object.
class Foo{
	void callMethod(){
		Toy toy = new Toy();
		toy.insertValue(this); //Here this means Foo current object
	}
}
Example of Case 3: Using this to call alternate constructors. In the comments, trinithis correctly pointed out another common use of this. When you have multiple constructors for a single class, you can use this(arg0, arg1, ...) to call another constructor of your choosing, provided you do so in the first line of your constructor.
class Foo {
    public Foo() {
        this("Some default value for bar");
        // Additional code here will be executed 
        // after the other constructor is done.
    }
    public Foo(String bar) {
        // Do something with bar
    }
    // ...
}

Save For Revision

Bookmark this item, mark it difficult, or place it in a revision set.

Open My Learning Library
Is it helpful? Yes No

Most helpful rated by users:

©2026 WithoutBook