以前只知道将对象写入文件用outPutStream,将文件读入到内存用inputStream，但是不知道为什么，今天有人讲解后终于知道了为什么，所以写到这里和大家分享，希望大家以后也不会弄混。
outputstream:是将对象从内存写入到外部，，相当于输出，所以用write()。
inputstream:是将外部内容读入到内存，所以是read（）。
写的一个demo如下：
package test;import java.io.FileInputStream;import java.io.FileOutputStream;import java.io.IOException;import java.io.ObjectInputStream;import java.io.ObjectOutputStream;import java.util.ArrayList;import java.util.HashMap;import java.util.List;import java.util.Map;public class TestFile {public static void main(String[] args) {new TestFile().writeObject();new TestFile().readObject();}public void writeObject() {FileOutputStream out;ObjectOutputStream objectOut = null;try {out = new FileOutputStream("D:/testFile.txt");objectOut = new ObjectOutputStream(out);} catch (Exception e) {e.printStackTrace();}List<Map<String, Object>> customers = new ArrayList<>();Map<String,Object> showMessage = new HashMap<>();showMessage.put("customer", "fiona");showMessage.put("waitTime", 14);Map<String,Object> showMessage2 = new HashMap<>();showMessage2.put("customer", "peter");showMessage2.put("waitTime", 15);customers.add(showMessage);customers.add(showMessage2);try {objectOut.writeObject(customers);} catch (IOException e) {e.printStackTrace();}}@SuppressWarnings("unchecked")public void readObject() {List<Map<String, Object>> customers = null;FileInputStream in;ObjectInputStream objectIn = null;try {in = new FileInputStream("D:/testFile.txt");objectIn = new ObjectInputStream(in);} catch (Exception e) {e.printStackTrace();}try {customers = (List<Map<String, Object>>) objectIn.readObject();} catch (ClassNotFoundException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}for(Map<String,Object> map:customers){for(String key : map.keySet()){System.out.println(key+":"+map.get(key));}}}}
打印结果：
customer:fionawaitTime:14customer:peterwaitTime:15
离开你的那一天开始，左心房渐渐停止跳动…
