java：IO流(获取文本上字符出现的次数)

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package com.heima.test;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.TreeMap;

public class test2 {

	public static void main(String[] args) throws IOException {
		BufferedReader br=new BufferedReader(new FileReader("xxx.txt"));
		TreeMap<Character, Integer> tm=new TreeMap<>();
		int ch;
		while((ch=br.read())!=-1) {
			char c=(char)ch;
			tm.put(c, !tm.containsKey(c)?1:tm.get(c)+1);//判断key是否包含在集合中，不包含写入集合中，包含获取key的数量+1
		}
		br.close();
		BufferedWriter bw=new BufferedWriter(new FileWriter("times.txt"));
		for(Character key:tm.keySet()) {
			switch(key) {
			case '\t':
				bw.write("\\t"+"="+tm.get(key));
				break;
			case '\n':
				bw.write("\\n"+"="+tm.get(key));
				break;
			case '\r':
				bw.write("\\r"+"="+tm.get(key));
				break;
			default:
				bw.write(key+"=="+tm.get(key));
				break;
			}
			
			bw.newLine();
		}
		bw.close();

	}

}