字符串的字符是否都不相同，输出重复的字符

public static boolean checkDifferent(String str) {

    if (str.isEmpty())return true;

     int[] flag=new int[128];

    //扫描字符串 for (int i = 0; i < str.length(); i++) {

    int c=(str.charAt(i));

    if (flag[c]>0) {

        System.out.println("str = " + str.charAt(i)); return false; }

        else { flag[c]++; } } return true;

}

输出字符串的数量

public static String findChar(){ 

String str="beautiful"; 

char[] chars = str.toCharArray(); 

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

for (char c : chars){ if(!(c>='a'&&c<='z'||c>='A'&&c<='Z')){ continue; }

 Integer count=map.get(c); //看数目。 

if (count == null){ map.put(c,1); }else { map.put(c,count+1); } }

 StringBuilder stringBuilder = new StringBuilder();

 for (Map.Entry<Character, Integer> m:map.entrySet()){ 

stringBuilder.append(m.getKey()+"("+m.getValue()+")"); }

 return stringBuilder.toString();}