How to Compare Two Strings in Java

Written by Rahul, Updated on August 17, 2019

code, example, java, programming, string, tutorial

Question – How do I compare two strings in the Java programming language?

Java provides two options for string compare. First is == operator and second is .equals() function for Java string compare. This Java tutorial will help you to understand string comparison under Java and difference between == and .equals() for string comparison in Java.

Operator == checks for the object reference and matches true if both string belongs to same object.
Function .equals() checks for the value of string, it doesn’t matter to which object they belongs.

Compare two Simple Strings

If both strings are simple strings. Java will consider them the same object. So both (== & equals()) will result as true.

public class StringCompare{

   public static void main(String args[]){
      String str1 = "hello world";
      String str2 = "hello world";

      System.out.println( str1 == str2 );       // Return True
      System.out.println( str1.equals(str2) );  // Return True
   }
}

public class StringCompare{

public static void main(String args[]){

String str1 = "hello world";

String str2 = "hello world";

System.out.println( str1 == str2 ); // Return True

System.out.println( str1.equals(str2) ); // Return True

}

Compare two String Objects

If both strings are object strings. Java will consider them different-2 objects. So == operator will return false and equals() function will result in true;

public class StringCompare{

   public static void main(String args[]){
      String str1 = new String("hello world");
      String str2 = new String("hello world");

      System.out.println( str1 == str2 );        // Return False
      System.out.println( str1.equals(str2) );   // Return True
   }
}

public class StringCompare{

public static void main(String args[]){

String str1 = new String("hello world");

String str2 = new String("hello world");

System.out.println( str1 == str2 ); // Return False

System.out.println( str1.equals(str2) ); // Return True

}

Compare one Simple String with one Object

If one is a simple string and other is an object string. Java will consider them different-2 objects. So == operator will return false and equals() function will result in true;

public class StringCompare{

   public static void main(String args[]){
      String str1 = "hello world";
      String str2 = new String("hello world");

      System.out.println( str1 == str2 );        // Return False
      System.out.println( str1.equals(str2) );   // Return True
   }
}

public class StringCompare{

public static void main(String args[]){

String str1 = "hello world";

String str2 = new String("hello world");

System.out.println( str1 == str2 ); // Return False

System.out.println( str1.equals(str2) ); // Return True

}

Compare with NULL String

But in case of comparison with null string == will return false but .equals() function will throw an exception. To avoid null exception we can use Objects.equals(str1, str2) function like following example.

import java.util.Objects;
public class StringCompare{

   public static void main(String args[]){
      String str1 = null;
      String str2 = new String("hello world");

      System.out.println(str1.equals(str2));		// Throw an Exception
      System.out.println(Objects.equals(str1, str2));	// Return False

   }
}

import java.util.Objects;

public class StringCompare{

public static void main(String args[]){

String str1 = null;

String str2 = new String("hello world");

System.out.println(str1.equals(str2)); // Throw an Exception

System.out.println(Objects.equals(str1, str2)); // Return False

}

Compare two Simple Strings

Compare two String Objects

Compare one Simple String with one Object

Compare with NULL String

Rahul

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