How to Compare two Strings in Java

In this tutorial, we’ll learn different ways to compare two strings in Java

Compare Strings using “==” operator

 1String string1 = "CodingNConcepts";
 2String string2 = "CodingNConcepts";
 3String string3 = new String("CodingNConcepts");
 4String string4 = new String("CodingNConcepts");
 5
 6System.out.println(string1 == string2);    // true
 7System.out.println(string1 == string3);    // false
 8System.out.println(string3 == string4);    // false
 9
10string3 = string3.intern();
11string4 = string4.intern();
12
13System.out.println(string1 == string3);    // true
14System.out.println(string3 == string4);    // true

Explanation

• line 6: string1 and string2 both are initialized using literal so they both are referring to same string stored in String-Pool
• line 7: string3 is initialized using New so it always creates a new string object in Java heap memory whereas string1 refers to string from String-Pool
• line 8: Since String initialized using New always create a new string object, string3 and string4 both refers to different string object in heap memory
• line 10,11: When you call intern() on a string, it returns a string from String-Pool if exist otherwise a new string is created in String-Pool and returned.
  So now after executing line 10 and 11, string3 and string4 refers to same string from String-Pool
• line 13,14: After executing line 10 and 11, all four strings string1, string2, string3 and string4 refers to same string from String-Pool

Compare Strings using equals() method

String’s equals() method – returns true if the string argument is not null and both the comparing strings have the same sequence of characters in same case.

1String string1 = "CodingNConcepts";
2String string2 = "CodingNConcepts";
3String string3 = new String("CodingNConcepts");
4String string4 = new String("CODINGNCONCEPTS");
5
6System.out.println(string1.equals(string2));   // true
7System.out.println(string1.equals(string3));   // true
8System.out.println(string1.equals(string4));   // false
9System.out.println(string1.equals(null));      // false

Explanation

• line 6: string1 and string2 both have same character sequence
• line 7: string1 and string3 both have same character sequence
• line 8: string1 and string4 both have same character sequence but case is different
• line 9: string argument is null