Remove Duplicate Characters from given string(Java)

package InterviewPrograms;

import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Set;

public class RemoveDuplicateFromString {
    public static void main(String[] args) {

        String str = "abbaaca";
        char y[] = str.toCharArray();
        int size = y.length;

        Map<Character, Integer> map = new LinkedHashMap<>();

        int i = 0;
        while (i != size) {
            if (map.containsKey(y[i]) == false) {
                map.put(y[i], 1);
            } else {
                int oldval = map.get(y[i]);
                int newval = oldval + 1;
                map.put(y[i], newval);
            }
            ++i;
        }
        Set<Map.Entry<Character, Integer>> lhmap = map.entrySet();
        String result = "";
        for (Map.Entry<Character, Integer> data : lhmap) {
            result = result + data.getKey();
        }
        System.out.println(result);
    }
}