以前只知道將物件寫入檔案用outPutStream,將檔案讀入到記憶體用inputStream，但是不知道為什麼，今天有人講解後終於知道了為什麼，所以寫到這裡和大家分享，希望大家以後也不會弄混。

outputstream:是將物件從記憶體寫入到外部，相當於輸出，所以用write()。

inputstream:是將外部內容讀入到記憶體，所以是read（）。

寫的一個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));
}
}
}
}

列印結果：

customer:fiona
waitTime:14
customer:peter
waitTime:15