equals() and ==

String comparison in Java

What is the difference between using equals() and == for string comparison in Java?

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In Java, equals() and == are both used for string comparison, but they serve different purposes due to the underlying mechanisms they employ.

1. equals() Method:

The equals() method in Java is used to compare the contents of two strings. When you use equals(), it checks whether the actual characters within the strings are the same or not.

Example:

        

javaCopy codeString str1 = "hello";
String str2 = "hello";
String str3 = new String("hello");

System.out.println(str1.equals(str2)); // Output: true
System.out.println(str1.equals(str3)); // Output: true

In this example, str1 and str2 are string literals, and str3 is created using the new keyword. Despite the difference in creation, the equals() method returns true because the contents of the strings are the same.

2. == Operator:

The == operator in Java checks whether two references point to the same memory location or not. When used with strings, it checks if both strings refer to the same object in memory.

Example:

        

javaCopy codeString str1 = "hello";
String str2 = "hello";
String str3 = new String("hello");

System.out.println(str1 == str2); // Output: true
System.out.println(str1 == str3); // Output: false

Here, str1 and str2 are string literals, so they refer to the same memory location. Hence, == returns true. However, str3 is created using the new keyword, so it refers to a different memory location, resulting in false.

Key Differences:

  • equals() compares the actual contents of the strings, while == compares the memory addresses or references.
  • equals() is overridden in the String class to provide content comparison, whereas == is used for reference comparison.
  • For most string comparison scenarios, equals() is preferred as it checks for content equality, which is usually the intended behavior.

Conclusion:

In summary, equals() and == serve different purposes for string comparison in Java. While equals() checks for content equality, == checks for reference equality. It’s essential to choose the appropriate method based on the desired comparison criteria in your Java applications.