Is there a class in Java which keeps duplicates but not order of data?

Question

I am dealing with anagrams so I'm concerned only with the characters present in the string but not their order. I searched for a suitable Collection class but in vain.

Can you please suggest any class that could help me to keep duplicates but ignores order?

Answer 1

You can use a Map<Character,Integer> to count the number of occurrences of each character of a String. If the Maps generated for two Strings are equal, you'll know that the corresponding Strings are anagrams.

For example (here I used Map<Integer,Long> instead of Map<Character,Integer> since it was more convenient):

String one = "animal";
String two = "manila";
Map<Integer,Long> mapOne = one.chars ().boxed().collect(Collectors.groupingBy(Function.identity(),Collectors.counting()));
Map<Integer,Long> mapTwo = two.chars ().boxed().collect(Collectors.groupingBy(Function.identity(),Collectors.counting()));
System.out.println ("Is anagram? " + mapOne.equals(mapTwo));

Output:

Is anagram? true

Answer 2

You can use Google guava's HashMultiSet. The equals() method does exactly that:

Compares the specified object with this multiset for equality. Returns true if the given object is also a multiset and contains equal elements with equal counts, regardless of order. This implementation returns true if object is a multiset of the same size and if, for each element, the two multisets have the same count.