Java Program example to demonstrate String compareToIgnoreCase method

Program

public class StringCompareToIgnoreCase
{
        public static void main(String[] args)
        {
                String str1 = "Welcome to oodlescoop";
                String str2 = "Welcome to oodlescoop";
                String str3 = "Hello all";
                String str4 = "Welcome to oodlescoop tutorials";
                String str5 = "WELCOME TO OODLESCOOP";
                System.out.println(str1.compareToIgnoreCase(str2) + "\t: strings are equal");
                System.out.println(str1.compareToIgnoreCase(str3) + "\t: first string is greater");
                System.out.println(str1.compareToIgnoreCase(str4) + "\t: second string is greater");
                System.out.println(str1.compareToIgnoreCase(str5) + "\t: equal inspite of case of the text");
        }
}

Purpose

This Java program demonstrates how to compare strings lexicographically while ignoring case differences using the compareToIgnoreCase method of the String class.

1. Class Definition

public class StringCompareToIgnoreCase

• Defines the class StringCompareToIgnoreCase.

2. Main Method

public static void main(String[] args)

• Entry point for the program.

3. Define Strings

String str1 = "Welcome to oodlescoop";
String str2 = "Welcome to oodlescoop";
String str3 = "Hello all";
String str4 = "Welcome to oodlescoop tutorials";
String str5 = "WELCOME TO OODLESCOOP";

• str1 and str2: Identical strings.
• str3: A string that is lexicographically smaller than str1.
• str4: A string that is lexicographically larger than str1.
• str5: Same as str1 but with all uppercase letters.

4. Compare Strings Using compareToIgnoreCase

System.out.println(str1.compareToIgnoreCase(str2) + "\t: strings are equal");
System.out.println(str1.compareToIgnoreCase(str3) + "\t: first string is greater");
System.out.println(str1.compareToIgnoreCase(str4) + "\t: second string is greater");
System.out.println(str1.compareToIgnoreCase(str5) + "\t: equal inspite of case of the text");

• compareToIgnoreCase Method:
  • Compares two strings lexicographically, ignoring case differences.
  • Returns:
    • 0: If the two strings are equal when case is ignored.
    • A positive number: If the first string is lexicographically greater.
    • A negative number: If the first string is lexicographically smaller.

Detailed Explanation of Comparisons

1. Compare str1 and str2

str1.compareToIgnoreCase(str2)

• Both strings are identical, and case is the same.
• Result: 0 (strings are equal).
• Output:

  0	: strings are equal
  

2. Compare str1 and str3

str1.compareToIgnoreCase(str3)

• str1: "Welcome to oodlescoop".
• str3: "Hello all".
• Lexicographically, "Welcome to oodlescoop" is greater because 'W' comes after 'H' in Unicode order, ignoring case.
• Result: A positive number.
• Output:

  15	: first string is greater
  

3. Compare str1 and str4

str1.compareToIgnoreCase(str4)

• str1: "Welcome to oodlescoop".
• str4: "Welcome to oodlescoop tutorials".
• Lexicographically, str1 is smaller because str4 has additional characters.
• Result: A negative number.
• Output:

  -9	: second string is greater
  

4. Compare str1 and str5

str1.compareToIgnoreCase(str5)

• str1: "Welcome to oodlescoop".
• str5: "WELCOME TO OODLESCOOP".
• Ignoring case, both strings are identical.
• Result: 0 (strings are equal).
• Output:

  0	: equal inspite of case of the text
  

Key Points About compareToIgnoreCase

1. Case-Insensitive Comparison:

   • It ignores the case of the characters when comparing.
   • For example:
     • 'a' is considered equal to 'A'.

2. Lexicographical Order:

   • Even though case is ignored, the method still compares characters lexicographically.

3. String Length:

   • If two strings are identical up to the length of the shorter string, the longer string is considered greater.

Output

0	: strings are equal
15	: first string is greater
-10	: second string is greater
0	: equal inspite of case of the text