Explain the difference between == and equals() in Java.

Question

Ashutosh Patel · Answer

Difference Between ‘==’ and equal()

“==” and “equals()” are used to compare objects, but they serve different purposes,

“==” (equality operator)

The == operator checks if the reference is equal. In other words, it checks whether two references refer to the same memory location, indicating that they do the same thing.

For primitive data types (such as int, double, etc.), == ensures that values are equal.

Example-

String str1 = new String("hello");
String str2 = new String("hello");
String str3 = str1;
System.out.println(str1 == str2); // false, different objects
System.out.println(str1 == str3); // true, same object reference

equals() method

The equals() method is a method defined in the Object class to ensure value equality (and overridden in many classes such as String and Integer).
By default, equals() of the Object class behaves like == (i.e., checks for reference equality). However, many classes override equals() to compare contents or values of objects.

Example-

String str1 = new String("hello");
String str2 = new String("hello");
System.out.println(str1.equals(str2)); // true, contents are equal

In example above

equals() compares the contents of str1 and str2 (i.e. their character sequences), and since they are both "hello", it returns true.

Key Differences

Purpose- == checks for reference equality or value equality for a primitive, while equals() is used to check content or value equality.
Usage- Use == to check if two references point to the same object instance. Use equals() to check if two objects are logically equivalent based on their internal state.
Overriding- While == cannot be overridden (because it is an operator), equals() can be overridden by classes to provide custom equality checks.

== Test whether two references point to the same thing.
equals() checks that two objects are logically equivalent based on their context or state, as defined by the class of the equals() function.

Also, Read: What is the significance of the 'final' keyword in Java?

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Explain the difference between == and equals() in Java.

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Difference Between ‘==’ and equal()

Key Differences