String comparison in Java

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Introduction

We compare strings to check if two pieces of text are the same or to find their order.

Checking if a user entered the correct password.

Sorting a list of names alphabetically.

Finding if two words are equal in a game.

Comparing input commands in a program.

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Syntax

Java

string1.equals(string2)
string1.equalsIgnoreCase(string2)
string1.compareTo(string2)

Use equals() to check if two strings have exactly the same characters.

Use equalsIgnoreCase() to compare strings ignoring uppercase or lowercase differences.

Use compareTo() to find the alphabetical order between two strings.

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Examples

line_end_arrow_notchChecks if both strings are exactly the same.

Java

String a = "hello";
String b = "hello";
boolean result = a.equals(b);

line_end_arrow_notchChecks if strings are the same ignoring case differences.

Java

String a = "Hello";
String b = "hello";
boolean result = a.equalsIgnoreCase(b);

line_end_arrow_notchReturns a negative number because "apple" comes before "banana" alphabetically.

Java

String a = "apple";
String b = "banana";
int result = a.compareTo(b);

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Sample Program

This program compares two strings using three methods and prints the results.

Java

public class Main {
    public static void main(String[] args) {
        String word1 = "Java";
        String word2 = "java";
        
        System.out.println("Using equals: " + word1.equals(word2));
        System.out.println("Using equalsIgnoreCase: " + word1.equalsIgnoreCase(word2));
        System.out.println("Using compareTo: " + word1.compareTo(word2));
    }
}

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Important Notes

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The equals() method is case sensitive.

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The compareTo() method returns 0 if strings are equal, a negative number if the first string is alphabetically before the second, and a positive number if after.

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Always use equals() or equalsIgnoreCase() to compare string content, not the == operator.

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Summary

Use equals() to check if two strings are exactly the same.

Use equalsIgnoreCase() to ignore letter case when comparing.

Use compareTo() to find alphabetical order between strings.