Q:

Need inputs about efficiency of my program for finding duplicates in String

I have developed a java program for checking if a string has all unique characters.  
I am listing it down.  I will appreciate if i get inputs about the efficiency of this program as well as any corrections needed to improve this program.  Thanks in advance. 
package com.string.duplicatechars;

import java.util. HashMap;
import java.util. Map;

public class CheckForDuplicateChars {

        /**
         * @param args
         */
        public static void main(String[] args) {
                String sampleString = "abcdabxyz";
                boolean allUniqueCharacters = allUniqueCharacters(sampleString);
                System.out.println("Are all characters unique: "+allUniqueCharacters);
        }

        public static boolean allUniqueCharacters(String sampleString) {
                boolean allUniquCharacters = true;
                char[] charArrForString = sampleString.toCharArray();
                Map<Character, Boolean> resultHashMap = new HashMap<Character, Boolean>();

                for(char ch: charArrForString){
                        Boolean isAlreadyPresent = (Boolean)resultHashMap.put(new Character(ch), new Boolean(true));

                        if(isAlreadyPresent ! = null){
                                if(isAlreadyPresent.booleanValue() == true) {
                                        System.out.println("Got repeated character: "+ch);
                                        allUniquCharacters = false;
                                }
                        } else {
                                System.out.println("Character "+ch+ " is being iserted first time");
                        }
                }

                return allUniquCharacters;
        }
}

A:

I would use a Set<Character> instead.  When you attempt to add a character to the set, it will return false if the set already contains that character. 
for(char c: yourCharArray){
    if(!set.add(c)){
        return false;
    }
}

