Strings in Java are objects that are supported internally by a char array. Since arrays are immutable, and strings are also a type of exceptional array that holds characters, therefore, strings are immutable as well.
The String class of Java comprises a lot of methods to execute various operations on strings such as compare(), concat(), equals(), split(), length(), replace(), compareTo(), substring(), etc. Out of these methods, we will be focusing on the Java String compareTo() method in this article.
Java String.compareTo() Method
The Java String class compareTo() method compares the given string with the current string lexicographically. It returns a positive number, a negative number, or 0. It compares strings on the basis of the Unicode value of each character in the strings.
- If the first string is lexicographically greater than the second string, it returns a positive number (difference of character value).
- If the first string is less than the second string lexicographically, it returns a negative number, and,
- If the first string is lexicographically equal to the second string, it returns 0.
Note:
- if string1 > string2, it returns positive number
- if string1 < string2, it returns negative number
- if string1 == string2, it returns 0
There are three variants of the compareTo() method which are as follows:
- using int compareTo(Object obj)
- using int compareTo(String anotherString)
- using int compareToIgnoreCase(String str)
1. int compareTo(Object obj)
This method compares this String to another Object.
Syntax:
int compareTo(Object obj)
Parameters:
obj: the Object to be compared.
Return Value:The value 0 if the argument is a string lexicographically equal to this string; a value less than 0 if the argument is a string lexicographically greater than this string; and a value greater than 0 if the argument is a string lexicographically less than this string.
Below is the implementation of the above method:
Java
// Java code to demonstrate the// working of compareTo()public class Cmp1 { public static void main(String args[]) { // Initializing Strings String str1 = "neveropen"; String str2 = new String("neveropen"); String str3 = new String("astha"); // Checking if neveropen string // equates to neveropen object System.out.print( "Difference of neveropen(obj) and neveropen(str) : "); System.out.println(str1.compareTo(str2)); // Checking if neveropen string // equates to astha object System.out.print( "Difference of astha(obj) and neveropen(str) : "); System.out.println(str1.compareTo(str3)); }} |
Difference of neveropen(obj) and neveropen(str) : 0 Difference of astha(obj) and neveropen(str) : 6
2. int compareTo(String anotherString)
This method compares two strings lexicographically.
Syntax:
int compareTo(String anotherString)
Parameters:
anotherString: the String to be compared.
Return Value: The value 0 if the argument is a string lexicographically equal to this string; a value less than 0 if the argument is a string lexicographically greater than this string; and a value greater than 0 if the argument is a string lexicographically less than this string.
Below is the implementation of the above method:
Java
// Java code to demonstrate the// working of compareTo()public class Cmp2 { public static void main(String args[]) { // Initializing Strings String str1 = "neveropen"; String str2 = "neveropen"; String str3 = "astha"; // Checking if neveropen string // equates to neveropen string System.out.print( "Difference of neveropen(str) and neveropen(str) : "); System.out.println(str1.compareTo(str2)); // Checking if neveropen string // equates to astha string System.out.print( "Difference of astha(str) and neveropen(str) : "); System.out.println(str1.compareTo(str3)); }} |
Difference of neveropen(str) and neveropen(str) : 0 Difference of astha(str) and neveropen(str) : 6
3. int compareToIgnoreCase(String str)
This method compares two strings lexicographically, ignoring case differences.
Syntax:
int compareToIgnoreCase(String str)
Parameters:
str: the String to be compared.
Return Value: This method returns a negative integer, zero, or a positive integer as the specified String is greater than, equal to, or less than this String, ignoring case considerations.
Below is the implementation of the above method:
Java
// Java code to demonstrate the// working of compareToIgnoreCase()public class Cmp3 { public static void main(String args[]) { // Initializing Strings String str1 = "geeks"; String str2 = "gEEkS"; // Checking if neveropen string // equates to neveropen string // case sensitive System.out.print( "Difference of geeks and gEEkS (case sensitive) : "); System.out.println(str1.compareTo(str2)); // Checking if neveropen string // equates to astha string // case insensitive // using compareToIgnoreCase() System.out.print( "Difference of geeks and gEEkS (case insensitive) : "); System.out.println(str1.compareToIgnoreCase(str2)); }} |
Difference of geeks and gEEkS (case sensitive) : 32 Difference of geeks and gEEkS (case insensitive) : 0