.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:

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
  }
}