Java String compareTo()

class Main {
  public static void main(String[] args) {
    String str1 = "Learn Java";
    String str2 = "Learn Kolin";
    int result;

    // comparing str1 with str2
    result = str1.compareTo(str2);

    System.out.println(result);
  }
}

// Output: -1

Syntax of compareTo()

The syntax of the compareTo() method is:

string.compareTo(String str)

Here, string is an object of the String class.

compareTo() Parameters

The compareTo() method takes a single parameter.

• str - the string to be compared

compareTo() Return Value

• returns 0 if the strings are equal
• returns a negative integer if the string comes before the str argument in the dictionary order
• returns a positive integer if the string comes after the str argument in the dictionary order

Example: Java String compareTo()

class Main {
  public static void main(String[] args) {
    String str1 = "Learn Java";
    String str2 = "Learn Java";
    String str3 = "Learn Kolin";
    int result;

    // comparing str1 with str2
    result = str1.compareTo(str2);

    System.out.println(result);  // 0

    // comparing str1 with str3
    result = str1.compareTo(str3);

    System.out.println(result);  // -1

    // comparing str3 with str1
    result = str3.compareTo(str1);

    System.out.println(result);  // 1
  }
}

Here,

• str1 and str2 are equal. Hence, str1.compareTo(str2) returns 0.
• str1 comes before str3 in the dictionary order. Hence, str1.compareTo(str3) returns negative, and str3.compareTo(str1) returns positive.

Example 2: Check if Two Strings are Equal

class Main {
  public static void main(String[] args) {
    String str1 = "Learn Python";
    String str2 = "Learn Java";
        
    // if str1 and str2 are equal, the result is 0
    if (str1.compareTo(str2) == 0) {

      System.out.println("str1 and str2 are equal");
    }
    else {
      System.out.println("str1 and str2 are not equal");
    }
  }
}

Output

str1 and str2 are not equal

Example 3: compareTo() With Case

The compareTo() method takes the letter case (uppercase and lowercase) into consideration.

class Main {
  public static void main(String[] args) {
    String str1 = "Learn Java";
    String str2 = "learn Java";
    int result;

    // comparing str1 with str2
    result = str1.compareTo(str2);

    System.out.println(result);  // -32
  }
}

When "Learn Java" is compared to "learn Java", we do not get 0. It is because compareTo() takes the letter case into consideration.

Related Tutorial: Java String equals()