How to check if two Strings are Anagrams in Java

In this post, we will see how to check if two Strings are Anagrams in java.

Anagrams mean if two Strings have the same characters but in a different order.
For example: Angel and Angle are anagrams

There are many ways to check if Strings are anagrams in java. Some of them are:

Table of Contents

Using String methods
Using Arrays.sort()
Using count array
Using Guava’s Multiset
Other String Programs

Using String methods

Algorithm:

Pass two Strings word and anagram to method called isAnagramUsingStringMethods()
Iterate over first String word and get char c from it using charAt() method
If index of char c is -1 in second String anagram, then two strings are not anagrams
If index of char c is not equal to -1 in second String anagram, then remove the character from the String anagram.
If you get empty String in the end, then two Strings are anagrams of each other.


package org.arpit.java2blog;

public class StringAnagramMain {

    public static void main(String[] args) {

        String word = "java2blog";
        String anagram = "aj2vabgol";

        System.out.println("java2blog and aj2vabgol are anagrams :" + isAnagramUsingStringMethods(word, anagram));

    }

    public static boolean isAnagramUsingStringMethods(String word, String anagram) {
        if (word.length() != anagram.length())
            return false;

        for (int i = 0; i < word.length(); i++) {
            char c = word.charAt(i);
            int index = anagram.indexOf(c);
            // If index of any character is -1, then two strings are not anagrams
            // If index of character is not equal to -1, then remove the chacter from the
            // String
            if (index != -1) {
                anagram = anagram.substring(0, index) + anagram.substring(index + 1, anagram.length());
            } else
                return false;
        }
        return anagram.isEmpty();
    }

}

package org.arpit.java2blog;

public class StringAnagramMain {

public static void main(String[] args) {

String word = "java2blog";

String anagram = "aj2vabgol";

System.out.println("java2blog and aj2vabgol are anagrams :" + isAnagramUsingStringMethods(word, anagram));

}

public static boolean isAnagramUsingStringMethods(String word, String anagram) {

if (word.length() != anagram.length())

return false;

for (int i = 0; i < word.length(); i++) {

char c = word.charAt(i);

int index = anagram.indexOf(c);

// If index of any character is -1, then two strings are not anagrams

// If index of character is not equal to -1, then remove the chacter from the

// String

if (index != -1) {

anagram = anagram.substring(0, index) + anagram.substring(index + 1, anagram.length());

} else

return false;

}

return anagram.isEmpty();

}

When you run above program, you will get below output:


java2blog and aj2vabgol are anagrams :true

java2blog and aj2vabgol are anagrams :true

Using Arrays.sort()

You can simply sort both the Strings using Arrays.sort() method. If both the Strings are equal after Sorting, then these two Strings are anagram of each other.


package org.arpit.java2blog;

import java.util.Arrays;

public class AnagramUsingSort {

    public static void main(String[] args) {

        String word = "java2blog";
        String anagram = "aj2vabgol";

        System.out.println("java2blog and aj2vabgol are anagrams :" + isAnagramUsingArraySort(word, anagram));

    }

    public static boolean isAnagramUsingArraySort(String word, String anagram) {

        String sortedWord = sortChars(word);
        String sortedAnagram = sortChars(anagram);

        return sortedWord.equals(sortedAnagram);
    }

    public static String sortChars(String word) {
        char[] wordArr = word.toLowerCase().toCharArray();
        Arrays.sort(wordArr);
        return String.valueOf(wordArr);
    }
}

package org.arpit.java2blog;

import java.util.Arrays;

public class AnagramUsingSort {

public static void main(String[] args) {

String word = "java2blog";

String anagram = "aj2vabgol";

System.out.println("java2blog and aj2vabgol are anagrams :" + isAnagramUsingArraySort(word, anagram));

}

public static boolean isAnagramUsingArraySort(String word, String anagram) {

String sortedWord = sortChars(word);

String sortedAnagram = sortChars(anagram);

return sortedWord.equals(sortedAnagram);

}

public static String sortChars(String word) {

char[] wordArr = word.toLowerCase().toCharArray();

Arrays.sort(wordArr);

return String.valueOf(wordArr);

}

When you run above program, you will get below output:

java2blog and aj2vabgol are anagrams :true

Using count array

Here is another approach to find if two Strings are anagrams.

Pass two Strings str1 and str2 to method isAnagram()
If length of str1 and str2 are not same, then they are not anagrams
Create an array named count of 256 length
Iterate over first string str1
In each iteration, we increment count of first String str1 and decrement the count of second String str2
If count of any character is not 0 at the end, it means two Strings are not anagrams

This approach has time complexity of O(n), but it requires extra space for count Array.


package org.arpit.java2blog;

public class AnagramCountingMain {

    public static void main(String args[])
    {
        boolean isAnagram = isAnagram("Angle","Angle");
        System.out.println("Are Angle and Angel anangrams: "+isAnagram);
    }

    public static boolean isAnagram(String str1, String str2) {
        if (str1.length() != str2.length()) {
            return false;
        }
        int count[] = new int[256];
        for (int i = 0; i < str1.length(); i++) {
            count[str1.charAt(i)]++;
            count[str2.charAt(i)]--;
        }
        for (int i = 0; i < 256; i++) {
            if (count[i] != 0) {
                return false;
            }
        }
        return true;
    }
}

package org.arpit.java2blog;

public class AnagramCountingMain {

public static void main(String args[])

{

boolean isAnagram = isAnagram("Angle","Angle");

System.out.println("Are Angle and Angel anangrams: "+isAnagram);

}

public static boolean isAnagram(String str1, String str2) {

if (str1.length() != str2.length()) {

return false;

}

int count[] = new int[256];

for (int i = 0; i < str1.length(); i++) {

count[str1.charAt(i)]++;

count[str2.charAt(i)]--;

}

for (int i = 0; i < 256; i++) {

if (count[i] != 0) {

return false;

}

return true;

}

Are Angle and Angel anangrams: true

Using Guava’s Multiset

If you prefer to use Guava library’s inbuild method to check if two String are anagrams, then you can use MultiSet.

MultiSet allows multiple occurrences of each element and tracks the count of each element.

You need to add following dependency to pom.xml.


<dependency>
    <groupId>com.google.guava</groupId>
    <artifactId>guava</artifactId>
    <version>27.1-jre</version>
</dependency>

<groupId>com.google.guava</groupId>

<artifactId>guava</artifactId>

</dependency>

Here are the steps to use Multiset for checking if two Strings are anagram in Java.

Pass two Strings str1 and str2 to method isAnagram()
If length of str1 and str2 are not same, then they are not anagrams
Create two multisets ms1 and ms2 using HashMultiset.create() method
Iterate over first string str1
In each iteration, add character of first String str1 to ms1 and character of second String str2 to ms2
If ms1 and ms2 are equal after iteration, it means two Strings are not anagrams

Let’s see with the help of Example.


package org.arpit.java2blog;

import com.google.common.collect.HashMultiset;
import com.google.common.collect.Multiset;

public class AnagramMultiSet {

    public static void main(String args[])
    {
        boolean isAnagram = isAnagramMultiset("Angle","Angle");
        System.out.println("Are Angle and Angel anangrams: "+isAnagram);
    }

    public static boolean isAnagramMultiset(String str1, String str2) {
        if (str1.length() != str2.length()) {
            return false;
        }
        Multiset<Character> ms1 = HashMultiset.create();
        Multiset<Character> ms2 = HashMultiset.create();
        for (int i = 0; i < str1.length(); i++) {
            ms1.add(str1.charAt(i));
            ms2.add(str2.charAt(i));
        }
        return ms1.equals(ms2);
    }
}

package org.arpit.java2blog;

import com.google.common.collect.HashMultiset;

import com.google.common.collect.Multiset;

public class AnagramMultiSet {

public static void main(String args[])

{

boolean isAnagram = isAnagramMultiset("Angle","Angle");

System.out.println("Are Angle and Angel anangrams: "+isAnagram);

}

public static boolean isAnagramMultiset(String str1, String str2) {

if (str1.length() != str2.length()) {

return false;

}

Multiset<Character> ms1 = HashMultiset.create();

Multiset<Character> ms2 = HashMultiset.create();

for (int i = 0; i < str1.length(); i++) {

ms1.add(str1.charAt(i));

ms2.add(str2.charAt(i));

}

return ms1.equals(ms2);

}

Are Angle and Angel anangrams: true

Other String Programs

That’s all about how to check if two Strings are Anagrams in Java.

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How to check if two Strings are Anagrams in Java

Using String methods

Using Arrays.sort()

Using count array

Using Guava’s Multiset

Other String Programs

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