Java Program example to demonstrate String compareTo method

Program

public class StringCompareTo
{
	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.compareTo(str2) + "\t: strings are equal");
		System.out.println(str1.compareTo(str3) + "\t: first string is greater");
		System.out.println(str1.compareTo(str4) + "\t: second string is greater");
		System.out.println(str1.compareTo(str5) + "\t: unequal due to case of the text");
	}
}

Purpose

This Java program demonstrates the use of the compareTo method in the String class to compare two strings lexicographically.

1. Class Definition

public class StringCompareTo

• Defines the class StringCompareTo.

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 different case.

4. Compare Strings

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

• compareTo Method:
  • Compares two strings lexicographically.
  • Returns:
    • 0: If the two strings are equal.
    • A positive number: If the first string is lexicographically greater than the second.
    • A negative number: If the first string is lexicographically smaller than the second.
  • Case-sensitive comparison.

Detailed Explanation of Comparisons

1. Compare str1 and str2

str1.compareTo(str2)

• Both strings are identical.
• Result: 0 (strings are equal).
• Output:

  0	: strings are equal
  

2. Compare str1 and str3

str1.compareTo(str3)

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

  15	: first string is greater
  

3. Compare str1 and str4

str1.compareTo(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.compareTo(str5)

• str1: "Welcome to oodlescoop".
• str5: "WELCOME TO OODLESCOOP".
• Lexicographically, uppercase letters come before lowercase letters in ASCII.
• Result: A positive number.
• Output:

  32	: unequal due to case of the text
  

Key Points About compareTo

1. Lexicographical Order:

   • Comparison is based on the Unicode values of characters.
   • Characters are compared one by one until a difference is found or one string ends.

2. Case Sensitivity:

   • compareTo is case-sensitive:
     • Uppercase letters (A-Z) have smaller Unicode values than lowercase letters (a-z).

3. Length of Strings:

   • 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
32	: unequal due to case of the text