Anagram Check Techniques in DSA Java - Build from Scratch

Anagram Check Techniques

📖 Scenario: You are building a simple tool to check if two words are anagrams. An anagram means both words have the same letters in a different order, like "listen" and "silent".This tool can help in word games or puzzles where you need to find matching words.

🎯 Goal: Build a Java program that checks if two given strings are anagrams by comparing their sorted characters.

📋 What You'll Learn

Create two string variables with exact values

Create a helper variable to hold sorted characters

Implement logic to check if two strings are anagrams by sorting

Print the result as true or false

💡 Why This Matters

🌍 Real World

Anagram checking is useful in word games, puzzles, and text analysis to find matching words or detect rearrangements.

💼 Career

Understanding string manipulation and array sorting is fundamental for software development, especially in data processing and algorithm design.

1

Create two strings to compare

Create two string variables called word1 and word2 with values "listen" and "silent" respectively.

DSA Java

// Your code here

Hint

Use String word1 = "listen"; and String word2 = "silent";

2

Create sorted character arrays

Create two character arrays called chars1 and chars2 by converting word1 and word2 to character arrays. Then sort both arrays using java.util.Arrays.sort().

DSA Java

public class AnagramCheck {
    public static void main(String[] args) {
        String word1 = "listen";
        String word2 = "silent";
        // Your code here
    }
}

Hint

Use word1.toCharArray() and Arrays.sort() to prepare sorted arrays.

3

Check if sorted arrays are equal

Create a boolean variable called isAnagram and set it to the result of comparing chars1 and chars2 using java.util.Arrays.equals(chars1, chars2).

DSA Java

import java.util.Arrays;

public class AnagramCheck {
    public static void main(String[] args) {
        String word1 = "listen";
        String word2 = "silent";
        char[] chars1 = word1.toCharArray();
        char[] chars2 = word2.toCharArray();
        Arrays.sort(chars1);
        Arrays.sort(chars2);
        // Your code here
    }
}

Hint

Use boolean isAnagram = Arrays.equals(chars1, chars2); to compare sorted arrays.

4

Print the anagram check result

Print the value of isAnagram using System.out.println(isAnagram);.

DSA Java

import java.util.Arrays;

public class AnagramCheck {
    public static void main(String[] args) {
        String word1 = "listen";
        String word2 = "silent";
        char[] chars1 = word1.toCharArray();
        char[] chars2 = word2.toCharArray();
        Arrays.sort(chars1);
        Arrays.sort(chars2);
        boolean isAnagram = Arrays.equals(chars1, chars2);
        // Your code here
    }
}

Hint

Use System.out.println(isAnagram); to show the result.

Practice

1. What does it mean if two strings are anagrams of each other?

easy

A. They end with the same character

B. They have the same length but different characters

C. They start with the same character

D. They contain the same characters in any order

Solution

1. Step 1: Understand the definition of anagrams

   Anagrams are words or phrases made by rearranging the letters of another, using all original letters exactly once.

2. Step 2: Compare character sets

   If two strings have the same characters with the same frequency, they are anagrams regardless of order.

3. Final Answer:

   They contain the same characters in any order -> Option D

4. Quick Check:

   Anagrams = same characters any order [OK]

Hint: Check if sorted strings match to confirm anagrams [OK]

Common Mistakes:

• Thinking same length means anagrams
• Only comparing first or last characters
• Ignoring character frequency

2. Which Java code snippet correctly checks if two strings s1 and s2 are anagrams using sorting?

easy

A. char[] a1 = s1.toCharArray(); char[] a2 = s2.toCharArray(); Arrays.sort(a1); Arrays.sort(a2); return Arrays.equals(a1, a2);

B. Arrays.sort(s1.toCharArray()); Arrays.sort(s2.toCharArray()); return s1.equals(s2);

C. return s1.equalsIgnoreCase(s2);

D. return s1.length() == s2.length();

Solution

1. Step 1: Convert strings to char arrays and sort

   We must convert strings to char arrays because Arrays.sort works on arrays, not strings.

2. Step 2: Compare sorted arrays for equality

   After sorting, if arrays are equal, strings are anagrams. Use Arrays.equals to compare arrays.

3. Final Answer:

   char[] a1 = s1.toCharArray(); char[] a2 = s2.toCharArray(); Arrays.sort(a1); Arrays.sort(a2); return Arrays.equals(a1, a2); -> Option A

4. Quick Check:

   Sort char arrays and compare arrays [OK]

Hint: Sort char arrays, then compare with Arrays.equals [OK]

Common Mistakes:

• Sorting strings directly without converting to char arrays
• Using equals() on unsorted strings
• Comparing only lengths

3. What will be the output of the following Java code?

String s1 = "listen";
String s2 = "silent";
char[] a1 = s1.toCharArray();
char[] a2 = s2.toCharArray();
Arrays.sort(a1);
Arrays.sort(a2);
System.out.println(Arrays.equals(a1, a2));

medium

A. Runtime exception

B. false

C. true

D. Compilation error

Solution

1. Step 1: Convert and sort both strings

   Both strings "listen" and "silent" are converted to char arrays and sorted. Sorted arrays become ['e','i','l','n','s','t'] for both.

2. Step 2: Compare sorted arrays

   Since sorted arrays are identical, Arrays.equals(a1, a2) returns true.

3. Final Answer:

   true -> Option C

4. Quick Check:

   Sorted arrays match = true [OK]

Hint: Sort and compare arrays to check anagrams [OK]

Common Mistakes:

• Assuming order matters without sorting
• Confusing equals() on strings with arrays
• Forgetting to sort arrays

4. Identify the error in this Java method that checks if two strings are anagrams:

public boolean isAnagram(String s1, String s2) {
  if (s1.length() != s2.length()) return false;
  char[] a1 = s1.toCharArray();
  char[] a2 = s2.toCharArray();
  Arrays.sort(a1);
  Arrays.sort(a2);
  return a1.equals(a2);
}

medium

A. Using a1.equals(a2) compares references, not content

B. Missing length check before sorting

C. Sorting arrays is incorrect for anagram check

D. Method should return void, not boolean

Solution

1. Step 1: Understand array equality in Java

   Using a1.equals(a2) compares if both arrays are the same object, not their contents.

2. Step 2: Use correct method to compare arrays

   To compare contents, use Arrays.equals(a1, a2) instead of a1.equals(a2).

3. Final Answer:

   Using a1.equals(a2) compares references, not content -> Option A

4. Quick Check:

   Use Arrays.equals() for array content comparison [OK]

Hint: Use Arrays.equals() to compare array contents [OK]

Common Mistakes:

• Using equals() on arrays instead of Arrays.equals()
• Ignoring length check
• Returning wrong data type

5. You want to check if two strings are anagrams but ignoring case and spaces. Which approach is best?

hard

A. Compare strings directly with equalsIgnoreCase()

B. Remove spaces, convert to lowercase, then sort and compare char arrays

C. Count characters without removing spaces or changing case

D. Check if lengths are equal and first characters match

Solution

1. Step 1: Normalize strings by removing spaces and converting to lowercase

   Removing spaces and converting to lowercase ensures uniform comparison ignoring case and spaces.

2. Step 2: Sort char arrays and compare

   After normalization, convert to char arrays, sort them, and compare to check anagram status.

3. Final Answer:

   Remove spaces, convert to lowercase, then sort and compare char arrays -> Option B

4. Quick Check:

   Normalize then sort and compare [OK]

Hint: Normalize strings before sorting to ignore case and spaces [OK]

Common Mistakes:

• Not removing spaces before comparison
• Ignoring case differences
• Only comparing lengths or first characters