compareTo() function

compareTo()

The Java compareTo() method compares the given string with the current string lexicographically. It returns a positive number, a negative number, or 0. It compares strings based on the Unicode value of each character in the strings.

If there is no index position at which the characters of the strings differ and they differ in lengths, in this case compareTo returns the difference of the lengths of the strings.

Internal implementation of compare to method

int compareTo(String anotherString) {  
    int length1 = value.length;  
    int length2 = anotherString.value.length;  
    int limit = Math.min(length1, length2);  
    char v1[] = value;  
    char v2[] = anotherString.value;  

    int i = 0;  
    while (i < limit) {  
       char ch1 = v1[i];  
       char ch2 = v2[i];  
       if (ch1 != ch2) {  
          return ch1 - ch2;  
       }  
       i++;  
     }  
    return length1 - length2;  
}

Usage and examples :

 String a = "Hello";
 String b = "Hello";
 int u = a.compareTo(b);                //  0

 int v = "abc".compareTo("Abc");        // 32
 int w = "abc".compareTo("abd");        // -1
 int x = "abd".compareTo("abc");        //  1
 int y = "Green".compareTo("Greenery"); // -3
 int z = "Greenery".compareTo("Green"); //  3