Difference Between == and equals() in Java

In this article, I shall describe two basic equality checks in Java – reference equality and value equality. We'll compare them, show examples, and highlight the key differences between them.

Reference Equality

In Java, "==" is used for reference equality, which means that it checks whether two objects refer to the same memory location.

Here's an example:

String s1 = "hello";
String s2 = new String("hello");

if (s1 == s2) {
  System.out.println("s1 and s2 are the same object");
} else {
  System.out.println("s1 and s2 are different objects");
}

Output:

s1 and s2 are different objects

Description:

In this example, we create two String objects: s1 is created using a string literal, while s2 is created using the new keyword.

We use == to compare s1 and s2, we get the output "s1 and s2 are different objects" because s1 and s2 are stored in different memory locations, even though they have the same value.

Value Equality

Value equality takes place when two separate objects happen to have the same values or state.This compares values and is closely related to the Object's equals() method.

Here's an example:

String s1 = "hello";
String s2 = new String("hello");

if (s1.equals(s2)){ 
  System.out.println("s1 and s2 have the same value");
} else {
  System.out.println("s1 and s2 have different values");
}

Output:

s1 and s2 have the same value

Description:

In this example, we create two String objects: s1 is created using a string literal, while s2 is created using the new keyword.

We use equals to compare s1 and s2, we get the output "s1 and s2 have the same value" because the contents of s1 and s2 are the same.

Conclusion:

So, the main difference between "==" and "equals" in Java is that "==" compares the memory location of two objects, while "equals" compares the contents of two objects.