[java] this in equals method

I am looking at the equals method, and I see this and I don't understand what it means...I do understand them when I see it in constructors and some methods but its not clear to me when they are in equals method something like this:

(obj == this) ...what does this mean here ? where does it come from ?

I understand when it says something like this.name = name;

from a method like this

@Override public boolean equals(Object obj) {     if (obj == this) {         return true;     }     if (obj == null || obj.getClass() != this.getClass()) {         return false;     } 

sorry it might be a duplicate but I couldnt find anything...

This question is related to java this equals

The answer is


this refers to the current instance of the class (object) your equals-method belongs to. When you test this against an object, the testing method (which is equals(Object obj) in your case) will check wether or not the object is equal to the current instance (referred to as this).

An example:

Object obj = this; this.equals(obj); //true   Object obj = this; new Object().equals(obj); //false 

You are comparing two objects for equality. The snippet:

if (obj == this) {     return true; } 

is a quick test that can be read

"If the object I'm comparing myself to is me, return true"

. You usually see this happen in equals methods so they can exit early and avoid other costly comparisons.


this is the current Object instance. Whenever you have a non-static method, it can only be called on an instance of your object.


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