public boolean isPermutation(String s1, String s2){
		if(s1.length()!=s2.length()){
			return false;
		}
		Hashtable<Character , Integer> ht = new Hashtable<>();
		for(int i=0;i<s1.length();i++){
			char c = s1.charAt(i);
			if(ht.containsKey(c)){	
				int val = ht.get(c) +1;
				ht.put(c, val);
			}else{
				ht.put(c, 1);
			}
		}
		for(int i=0;i<s2.length();i++){
			char c = s2.charAt(i);
			if(ht.containsKey(c)){
				int val = ht.get(c);
				if(val==0){
					return false;
				}
				val--;
				ht.put(c, val);
			}else{
				return false;
			}
		}
		Set<Character> keys = ht.keySet();
		for(Character k :keys ){
			if(ht.get(k)!=0){
				return false;
			}
		}
		return true;
	}