面试试题002--数字母的个数

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package myjava;

import java.util.HashMap;
import java.util.Iterator;
import java.util.Set;

public class LetterCount {

    public static void main(String[] args) {

        String str = "ajsfkjjkejrfjajjjjj";
        HashMap hm = new HashMap();
        //char[] a = str.toCharArray();
        // System.out.println(a.length);
        for (int i = 0; i < str.length(); i++) {
            if (!hm.containsKey(str.charAt(i))) {
                hm.put(str.charAt(i), 1);
            } else {
                Integer count = (Integer) hm.get(str.charAt(i));
                count++;
                hm.put(str.charAt(i), count);
            }
        }
 Set key = hm.keySet();
 System.out.println("一共有"+key.size()+"个字母！");
for(Iterator itr = key.iterator();itr.hasNext();){
   Character letter =((Character)itr.next());
    System.out.print(letter+":      ");
   System.out.println(hm.get(letter));


}
    }
}