java实现计算出字符串中每个字母出现次数

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题目：java实现计算出字符串中每个字母出现次数

示例：

输入字符串为:aBcdenffdhanbcdeefe+- ..
输出字符串为:B(1)a(2)b(1)c(2)d(3)e(4)f(3)h(1)n(2)
括号内数字为前面字母出现次数

实现代码：

import java.util.Iterator;
import java.util.Map;
import java.util.TreeMap;
public class CountCharacter {
    public static void main(String[] args) {
        String str = "aBcdenffdhanbcdeefe+-  ..";
        System.out.println("输入字符串为:"+str);
        String count = countCharacter(str);
        System.out.println("输出字符串为:"+count);
        System.out.println("括号为前面字母出现次数");
    }
    public static String countCharacter(String str) {
        char[] c = str.toCharArray();
        Map<Character,Integer> map = new TreeMap<Character,Integer>();
        for(int i = 0;i<c.length;i++){
            Integer value = map.get(c[i]);
            if(!(c[i]>='a'&&c[i]<='z'||c[i]>='A'&&c[i]<='Z'))
                continue;
            if(value==null)
                map.put(c[i], 1);
            else
                map.put(c[i], value+1);
        }

        return maptoString(map);
    }
    private static String maptoString(Map<Character, Integer> map) {
        StringBuilder str = new StringBuilder();
        Iterator<Character> it = map.keySet().iterator();
        while(it.hasNext()){
            Character key = it.next();
            Integer value = map.get(key);
            str.append(key+"("+value+")");
        }
        return str.toString();
    }
}

输出结果：

输入字符串为:aBcdenffdhanbcdeefe+- ..
输出字符串为:B(1)a(2)b(1)c(2)d(3)e(4)f(3)h(1)n(2)
括号为前面字母出现次数