Introduction:

Strings are used all over in any Java application. So, it’s important to understand how to compare two string objects.

In this article, we’ll learn ways to compare String objects.

 

1.) Comparing References Using ‘==’

The == operator when used to compare strings is responsible for comparing only the references(not the content). So it will output true if two String references refer to the same object, false otherwise.

String str1 = "ProgrammerGirl"; //stored in String Pool
String str2 = new String ("ProgrammerGirl"); //Stored on heap
String str3 = "ProgrammerGirl"; //Referring to the one in String Pool

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

In the above example, although both str1 and str2 have the same content i.e. “ProgrammerGirl” but they are referring to two different objects, so str1 == str2 outputs false.

However, both str1 and str3 are referring to the same object stored in String Pool, so str1 == str3 outputs true.

2.) equals() method

String class in Java provides an equals() method which can be used to compare the string contents:

String str1 = "ProgrammerGirl";
String str2 = new String ("ProgrammerGirl");
String str3 = "programmerGirl";

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

System.out.println(str1.equals(str3)); //false

equals() method compares the value of String objects. Also, the comparison is case-sensitive. So if the two strings have exactly the same content equals() method outputs true, false otherwise.

3.) equalsIgnoreCase() method

The equalsIgnoreCase() method in Java help us achieve a non case-sensitive string content comparison.

String str1 = "ProgrammerGirl";
String str2 = new String ("ProgrammerGirl");
String str3 = "programmerGirl";

System.out.println(str1.equalsIgnoreCase(str2)); //true

System.out.println(str1.equalsIgnoreCase(str3)); //true

It simply ignores the character-casing while comparing the string object contents.

4.) compareTo() method

The compareTo() method in String compares the two string contents lexicographically and returns an integer value as an output. The method str1.compareTo(str2) would return:

• A positive value, if str1 is lexicographically greater than str2
• 0, if str1 is equal to str2
• A negative value, if str1 is lexicographically less than str2

String str1 = "ProgrammerGirl";
String str2 = "Program";
String str3 = "ProgrammerGirl";  

System.out.println(str1.compareTo(str2)); // 7 
System.out.println(str2.compareTo(str1)); // -7 
System.out.println(str1.compareTo(str3)); // 0

5.) compareToIgnoreCase() method

This method is exactly the same as compareTo(), except the fact that it ignores the character casing.

String str1 = "ProgrammerGirl";
String str2 = "Program";
String str3 = "programmergirl";  

System.out.println(str1.compareToIgnoreCase(str2)); // 7 
System.out.println(str2.compareToIgnoreCase(str1)); // -7 
System.out.println(str1.compareToIgnoreCase(str3)); // 0

Conclusion:

In this quick tutorial, we explored ways in which we can compare String objects in Java.