How to Compare two Strings in Java

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 Both Simple Strings:

If both string are simple strings. Java will consider them a 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 } }

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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 Both Strings are Objects:

If both string are an object strings. Java will consider them a 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 } }

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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 Strings and One Object:

If on is simple string and other is an object strings. Java will consider them a 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 } }

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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 } }

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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    } }

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