.compareTo()

The .compareTo() method compares two strings lexicographically based on the Unicode value of each character in the string.

Syntax

stringA.compareTo(stringB);

Both stringA and stringB are required in order for the .compareTo() method to work properly.

A value of 0 will be returned if the strings are equal. Otherwise, the following will happen:

  • A number less than 0 is returned if stringA is lexicographically less than stringB.
  • A number greater than 0 is returned if stringA is lexicographically more than stringB.

A way to think about this lexicographical evaluation is noting the Unicode values for the following character sets:

Character Set Range Example
1 - 9 49 - 57 "7".compareTo("3"); -> 55 - 51 = 4
A - Z 65 - 90 "A".compareTo("B"); -> 65 - 66 = -1
a - z 97 - 122 "z".compareTo("w"); -> 122 - 119 = 3

Note: This method is case-sensitive. The .compareToIgnoreCase() can be used to ignore upper and lower case differences. Alternatively, the .equals() method can used to compare strings without taking Unicode values into account.

Example 1

Compare "Codecademy" to "Codecademy":

class CompareStringsLexicographically {
public static void main(String[] args) {
String word1 = "Codecademy";
String word2 = "Codecademy";
System.out.println(word1.compareTo(word2));
// Output: 0
}
}

Example 2

Compare "Codecademy" to "codecademy":

class CompareStringsLexicographically {
public static void main(String[] args) {
String word1 = "Codecademy";
String word2 = "codecademy";
System.out.println(word1.compareTo(word2));
// Output: -32
}
}

Example 3

Compare "codecademy" to "Codecademy":

class CompareLexicographically {
public static void main(String[] args) {
String word1 = "codecademy";
String word2 = "Codecademy";
System.out.println(word1.compareTo(word2));
// Output: 32
}
}

Contributors

Interested in helping build Docs? Read the Contribution Guide or share your thoughts in this feedback form.

Learn Java on Codecademy