一個經典的Map+正則表達式練習題：給定一個帶其他文字的字母字符串，求出各個字符有多少個？

package com.test;

import java.util.HashMap;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class Test {
	public static void main(String[] args) {
		String str = "aaaaaannnnnnnnvvvva阿森納反覆vvvvasd阿薩德vvdddddddddddffffffasdadasdasdadasdasdasdasd";
                  //首先要先把中文去掉，使用正則表達式獲取字母；
               String s1 = getString(str);
		char[] ch = s1.toCharArray();
		Map<Character,Integer> map = new HashMap<Character,Integer>();
		for (int i = 0; i < ch.length; i++) {
			if(map.containsKey(ch[i])){
				int n = map.get(ch[i])+1;
				map.put(ch[i], n);
			}else{
				map.put(ch[i],1);
			}
		}
		System.out.println(map);
	}
	
	public static String getString(String str){
		Pattern p = Pattern.compile("[a-zA-Z]");
		StringBuffer buf = new StringBuffer();
		char[] c = str.toCharArray();
		for (int i = 0; i < c.length; i++) {
			Matcher m = p.matcher(c[i]+"");
			if(m.find()){
				buf.append(c[i]);
			}
		}
		return buf.toString();
	}
	
}