java去除字符串中重复、不重复、消除重复后字符

import java.util.HashSet;
import java.util.Set;

public class Main {

public static void main(String[] args) {
    String str = "aaasd";
    System.out.println("原字符串： "+str);
    Set<Character> set1 = new HashSet<Character>();
    Set<Character> set2 = new HashSet<Character>();
    Set<Character> set3 = new HashSet<Character>();
    //把字符串转为字符数组
    char[] cs = str.toCharArray();
    //便利字符数组aaasd
    for(char c:cs){
        //把遍历的字符加入set1（HashSet,无序不可重复）
        boolean b = set1.add(c);//asd
        if(!b){
            //b不等空就是有重复的字符,重复的字符加入set2
            set2.add(c);//a
        }
    }
    //把消除重复后的字符set1赋给Set3
    set3.addAll(set1);//asd
    //把消除的重复后的字符set1 - 重复的字符set2 = 不重复的字符
    set3.removeAll(set2);//asd-a = sd
    System.out.println("=========消除重复厚的字符=========");
    for ( char c : set1){
        System.out.print(c + "");
    }
    System.out.println("\n===========重复的字符===============");
    for (char c :set2){
        System.out.print(c + "");

    }
    System.out.println("\n========不重复的数组===========");
    for (char c :set3){
        System.out.print(c + "");
    }

}

}

原文：http://blog.51cto.com/13579083/2329972