CodingGyan

String Equality: Content vs Reference

beginner Programming Basics

Problem

Read two words, one on each line. Print equals: true if both words have exactly the same characters, else equals: false. Then print ignoring case: true if they are the same when upper and lower case letters are treated alike, else ignoring case: false.

Constraints

  • Words have 1 to 100 letters or digits, no spaces

Examples

Input

Java
java

Output

equals: false
ignoring case: true

Solutions

Best approachTime O(n)Space O(1)

In Java, == on two strings asks if they are the same object. equals asks if they have the same characters. Beginners often use == by mistake and get wrong answers.

Same code works in Java810172125Basic features only, so nothing changes between versions.
/*
 * Problem : Compare two words.
 * Input   : Two lines, one word on each line.
 * Output  : Two lines: equals and ignoring case.
 * Approach: Compare the content, not the memory address.
 * Time    : O(n)
 * Space   : O(1)
 * Java    : 8 or newer.
 */
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String first = scanner.nextLine();
        String second = scanner.nextLine();

        // Step 1: Use equals to compare the characters. Do not use ==, it compares memory addresses.
        boolean same = first.equals(second);

        // Step 2: Use equalsIgnoreCase to ignore upper and lower case.
        boolean sameIgnoringCase = first.equalsIgnoreCase(second);

        // Step 3: Print both answers.
        System.out.println("equals: " + same);
        System.out.println("ignoring case: " + sameIgnoringCase);
    }
}
Hints (1)
  1. What does == compare for objects in Java?