Java String Compare

In Java, you can compare strings using several different approaches. In this tutorial, we will write various Java programs to compare Strings in java.

1. Using equal to operator (==)
2. Using equals() method of String class
3. compareTo() method of String class
4. Using compareToIgnoreCase() method
5. Using contentEquals() method

1. Comparing two strings by using == operator

In the following program we are using equal to operator == to compare two strings. This operator returns true if the string references are equal else it returns false. The program is self explanatory, we have created two strings with the same value, when we compared them using ==, it returned true so the statement inside if statement got executed.

class JavaExample{
  public static void main(String args[]){
    String website="BeginnersBook";
    String website2="BeginnersBook";
    if(website == website2)
      System.out.println("Both Strings are Equal");
    else
      System.out.println("Both Strings are Not Equal");
  }
} 

Output:

Both Strings are Equal

Note: The == operator only compares the String references so if you are creating a new instance of the String class then you should not use == operator. It will return false, even if the string value is same. For this, you should use the equals() method of String class, which we have discussed below.

2. Compare two strings using equals() method

As I have mentioned in the Note in the above section, when we create a new instance of the String, we should not use == operator for comparing these strings as it only compares the references of the Strings. We should use the equals() method for such scenarios.

In the following example we have two strings which are same but we have called String class constructor to create these strings. It created a new instance for both of these strings that is the reason, the == operator returned false, even though the strings are same. However the method returned true as expected.

public class JavaExample {

  public static void main(String[] args) {

    String name = new String("Chaitanya");
    String name2 = new String("Chaitanya");

    System.out.print("Comparison using equals() method: ");
    if(name.equals(name2))
      System.out.println("Strings are Equal");
    else
      System.out.println("Strings are Not Equal");

    System.out.print("Comparison using == operator: ");
    if(name==name2)
      System.out.println("Strings are Equal");
    else
      System.out.println("Strings are Not Equal");
  }
}

Output:

Comparison using equals() method: Strings are Equal
Comparison using == operator: Strings are Not Equal

Example 2: Comparing two strings while ignoring the case

Method equals() is a case-sensitive method, to compare the strings where we need to ignore the case, we can use an alternative method of String class, which is equalsIgnoreCase().

class JavaExample{
  public static void main(String args[]){
    String name="Carl";
    String name2="CARL";

    System.out.println(name.equals(name2));
    System.out.println(name.equalsIgnoreCase(name2));
  }
} 

Output:

false
true

3. Java String compare: using compareTo() method

The compareTo() method compares the strings and returns an int value, if the strings are equal it returns 0 else it returns an int value (negative if string is less than other string, positive if string is greater than other string).

class JavaExample{
  public static void main(String args[]){
    String name="Steve";
    String name2="Steve";

    if(name.compareTo(name2)==0)
      System.out.println("Strings are equal");
    else
      System.out.println("Strings are not equal");
  }
}  

Output:

Strings are equal

4. Using compareToIgnoreCase() Method

This method works exactly same as compareTo() method except that it ignores the case during comparison, which means comparison done by this method is not case-sensitive. I have covered this method in detail here: String compareToIgnoreCase()

String str1 = "Apple";
String str2 = "apple";

int result = str1.compareToIgnoreCase(str2); // 0

5. Using contentEquals() Method

The contentEquals() method of String class compares the string with CharSequence, such as a StringBuilder, StringBuffer, or any other class that implements the CharSequence interface.

• The comparison is case-sensitive.
• It returns true if the content matches else it returns false.
• This method is mostly used when you need to compare a String with sequence-based objects.

public class ContentEqualsExample {
    public static void main(String[] args) {
        String str = "hello";
        
        StringBuilder sb = new StringBuilder("hello");
        StringBuffer sf = new StringBuffer("hello");
        CharSequence cs = "hello";
        
        // Comparing String with StringBuilder
        boolean result1 = str.contentEquals(sb);
        // Output: true
        System.out.println("str and sb content equals: " + result1); 
        
        // Comparing String with StringBuffer
        boolean result2 = str.contentEquals(sf);
        // Output: true
        System.out.println("str and sf content equals: " + result2);
        
        // Comparing String with CharSequence
        boolean result3 = str.contentEquals(cs);
        // Output: true
        System.out.println("str and cs content equals: " + result3);
        
        // Comparing String with different StringBuilder
        StringBuilder sbDifferent = new StringBuilder("world");
        boolean result4 = str.contentEquals(sbDifferent);
        // Output: false
        System.out.println("str and sbDifferent content equals: " + result4);
    }
}

To learn more about this method refer: String contentEquals()

Conclusion

We learned three ways to compare java strings. Lets summarise these points:

• You should use equals() method when you want to compare strings without ignoring case. If you do not want to consider the case for comparison then use equalsIgnoreCase().
• Use compareTo() method when you do not want true or false as a result of string comparison, this is especially useful when you are sorting the strings in alphabetical order like dictionary.
• == operator should only be used for string references comparison.
• Use contentEquals() method when you want to compare string with a char sequence objects such as StringBuilder or StringBuffer.