.compareTo()

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

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.

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
  }
}

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
  }
}

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
  }
}