获取字符串中每个字符出现的次数

写作背景：闲来无事，忽然想到之前同事问我的一个问题，觉得有点意思记录一下

那么问题呢如题所示

下面我就直接贴出我的代码了：

package com.testcode;

import java.util.HashSet;
import java.util.Iterator;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class CharCount {
	public static void main(String[] args) {
		String str = "aaaccddtkdffdafdf tghf v";
		long startTime = System.currentTimeMillis();
		getCharCount(str);
		System.out.println("耗时 ：" + (System.currentTimeMillis()  -startTime));
		
		long startTime1 = System.currentTimeMillis();
		getCharCount2(str);
		System.out.println("耗时 ：" + (System.currentTimeMillis()  -startTime1));
	}

	private static void getCharCount(String str) {
		char[] chs = str.toCharArray();
		HashSet<String> hashSet = new HashSet<>();
		for (int i = 0; i < chs.length; i++) {
			hashSet.add(chs[i] + "");
		}
		Iterator<String> iterator = hashSet.iterator();
		for (String s; iterator.hasNext();) {
			s = iterator.next();
			Pattern compile = Pattern.compile(s);
			Matcher matcher = compile.matcher(str);
			int a = 0;
			while (matcher.find()) {
				a++;
			}
			System.out.println(s + " count : " + a);
		}
	}

	private static void getCharCount2(String str) {
		char[] chs = str.toCharArray();
		String tmp;

		HashSet<String> hashSet = new HashSet<>();
		for (int i = 0; i < chs.length; i++) {
			hashSet.add(chs[i] + "");
		}
		Iterator<String> iterator = hashSet.iterator();
		for (String s; iterator.hasNext();) {
			tmp = iterator.next();
			int count = 0;
			for (int j = 0; j < chs.length; j++) {
				if (chs[j] == tmp.charAt(0)) {
					count++;
				}
			}
			System.out.println("char " + tmp + " count :" + count);
		}
	}
}

运行结果：

f count : 5
v count : 1
g count : 1
  count : 2
d count : 5
t count : 2
c count : 2
a count : 4
k count : 1
h count : 1
耗时 ：2
char f count :5
char v count :1
char g count :1
char   count :2
char d count :5
char t count :2
char c count :2
char a count :4
char k count :1
char h count :1
耗时 ：0

方法1是百度来的觉得也是一种思路，方法2是我自己想到的效率高一点。