How to Check Anagram in Java

What is an Anagram?

An anagram is a word formed by rearranging the letters of another word. Examples: "listen" and "silent", "triangle" and "integral"

Solutions

Method 1: Using Sorting

java

import java.util.Arrays;

public static boolean isAnagram(String str1, String str2) {
    // Remove spaces and convert to lowercase
    str1 = str1.replaceAll("\\s", "").toLowerCase();
    str2 = str2.replaceAll("\\s", "").toLowerCase();
    
    // Check if lengths are different
    if (str1.length() != str2.length()) {
        return false;
    }
    
    // Sort both strings and compare
    char[] arr1 = str1.toCharArray();
    char[] arr2 = str2.toCharArray();
    Arrays.sort(arr1);
    Arrays.sort(arr2);
    
    return Arrays.equals(arr1, arr2);
}

// Usage
System.out.println(isAnagram("listen", "silent")); // true
System.out.println(isAnagram("hello", "world"));   // false

Method 2: Using Character Count

java

public static boolean isAnagram(String str1, String str2) {
    str1 = str1.replaceAll("\\s", "").toLowerCase();
    str2 = str2.replaceAll("\\s", "").toLowerCase();
    
    if (str1.length() != str2.length()) {
        return false;
    }
    
    int[] count = new int[26];
    
    for (int i = 0; i < str1.length(); i++) {
        count[str1.charAt(i) - 'a']++;
        count[str2.charAt(i) - 'a']--;
    }
    
    for (int c : count) {
        if (c != 0) {
            return false;
        }
    }
    
    return true;
}

// Usage
System.out.println(isAnagram("triangle", "integral")); // true

Did You Know?

The longest one-word anagrams in English are "conversationalists" and "conservationalists" - both have 18 letters!

Pro Tip

The character count method is more efficient (O(n)) than sorting (O(n log n)) for large strings!

Real-World Use Cases

Word games: Scrabble, anagram solvers
Cryptography: Simple encryption techniques
Plagiarism detection: Identify rearranged text
Data deduplication: Find similar entries

›Short versionOpen if you only have a minute.

Same characters, same counts, order ignored. "listen" and "silent" match.
Sorting both char arrays is O(n log n). A frequency count is linear.
An int[26] indexed by c - 'a' throws as soon as a space, a digit, or an uppercase letter appears.
toLowerCase() without Locale.ROOT follows the default locale. Turkish I does not fold to i.

Anagram check

Decide whether two strings contain the same characters with the same frequencies.

Working approach

If the contract ignores spaces and case, normalize both copies with Locale.ROOT first.
Reject a length mismatch after that normalization.
Count with a map when the alphabet is not known to be a-z. Use int[26] only after you have checked that every char is in range.

Walk the sample

"listen" and "silent"
Lengths match
Each letter increments on one side and decrements on the other
Every count ends at 0

The trap

count[c - 'a'] assumes every remaining character is a lowercase English letter. A space makes a negative index.

java

static boolean sameLetters(String a, String b) {
    if (a.length() != b.length()) {
        return false;
    }
    int[] count = new int[26];
    for (int i = 0; i < a.length(); i++) {
        int left = a.charAt(i) - 'a';
        int right = b.charAt(i) - 'a';
        if (left < 0 || left >= 26 || right < 0 || right >= 26) {
            throw new IllegalArgumentException("expected lowercase a-z");
        }
        count[left]++;
        count[right]--;
    }
    for (int n : count) {
        if (n != 0) {
            return false;
        }
    }
    return true;
}

What does count[c - 'a'] do when c is a space?

' ' - 'a' is negative. The write into the 26-slot array throws ArrayIndexOutOfBoundsException.

Strip or reject out-of-range characters before indexing, or count with a Map. Also fold case with Locale.ROOT so a Turkish default locale does not turn I into ı.

A count is O(n) time. Sorting is O(n log n). Space depends on the alphabet, not on the length, for a fixed map.

Easy to get wrong

Indexing a 26-slot array with arbitrary text.
Comparing lengths before removing the spaces the contract told you to ignore.