String Permutation

Given two strings, write a method to decide if one is a permutation of the other.

Example

abcd is a permutation of bcad, but abbe is not a permutation of abe

 1 public class Solution {
 2     /**
 3      * @param A a string
 4      * @param B a string
 5      * @return a boolean
 6      */
 7     public boolean stringPermutation(String A, String B) {
 8         // Write your code here
 9         if(A==null&&B==null){
10             return true;
11         } else if (A==null||B==null||A.length()!=B.length()){
12             return false;
13         }
14         Map<Character, Integer> a = new HashMap<Character, Integer>();
15         
16         for(char c : A.toCharArray()){
17             if(!a.containsKey(c))
18                 a.put(c, 1);
19             else
20                 a.put(c, a.get(c)+1);
21             
22             //a.put(c, a.getOrDefault(c, 0) + 1);
23         }
24         for(char c : B.toCharArray()){
25             if(!a.containsKey(c) || a.get(c)==0){
26                 return false;
27             }
28             a.put(c, a.get(c)-1);
29         }
30         return true;
31     }
32 }