1.

ObjectInputStream与ObjectOutputStream类所读写的对象必须实现Serializable接口，对象中的transient和static类型成员变量不会被读取和写入

2.

Serializable是个对象序列化接口，只有序列化才能实现对象存取

3.

//定义学生类

package job;

import java.io.Serializable;
import java.util.Set;

public class Student implements Serializable{    //注意序列化对象
 private static final long serialVersionUID = -7311905363747695209L;
 private String name;
 private int age;
 private int id;
 public String getName() {
  return name;
 }
 public void setName(String name) {
  this.name = name;
 }
 public int getAge() {
  return age;
 }
 public void setAge(int age) {
  this.age = age;
 }
 public int getId() {
  return id;
 }
 public void setId(int id) {
  this.id = id;
 }
 public Student(String name, int age, int id) {
  super();
  this.name = name;
  this.age = age;
  this.id = id;
 }
 public Student() {
  super();
  // TODO 自动生成的构造函数存根
 }
 }

//利用动态数组 存取对象

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package job;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.OutputStream;
import java.util.ArrayList;

public class ObjectStreamDemo {
 public static void main(String[] args) throws Exception, ClassNotFoundException {
  //建立文件
  OutputStream f = new FileOutputStream("a.txt");
  //new 两个对象为存储做准备
  Student stu = new Student("张三", 16, 1001);
  Student stu1 = new Student("李四", 15, 1002);
  //构造列表并存入对像
  ArrayList<Object> link = new ArrayList<Object>();
  link.add(stu);
  link.add(stu1);
  //将列表转化为对象数组
  Object[] stuarr = link.toArray();
  //利用对象数组写入文件
  ObjectOutputStream oos = new ObjectOutputStream(f);
  oos.writeObject(stuarr);
  oos.close();
  //读取对象
  InputStream fi = new FileInputStream("a.txt");
  ObjectInputStream ois = new ObjectInputStream(fi);
  //读取对象到对象数组
  Object[] obj = (Object[]) ois.readObject();
  for (int i = 0; i < obj.length; i++) {
   Student s = (Student) obj[i];
   System.out.print("姓名" + s.getName() + "\t");
   System.out.print("年龄" + s.getAge() + "\t");
   System.out.println("学好" + s.getId());
  }
  ois.close();
 }

}

4.

另外一种方法 （FileOutputStream(fn, true)追加对象）

package com;

import java.io.IOException;
import java.io.ObjectOutputStream;
import java.io.OutputStream;

public class My extends ObjectOutputStream {
 public My() throws IOException {
  super();
 }

 public My(OutputStream out) throws IOException {
  super(out);
 }

 @Override
 protected void writeStreamHeader() throws IOException {
  return;
 }

}

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package com;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.text.ParseException;
import java.text.SimpleDateFormat;

public class ObjectStreamDemo {

 public static void main(String[] args) throws FileNotFoundException, IOException, ParseException, ClassNotFoundException {
  SimpleDateFormat sdf = new SimpleDateFormat("yyyy年MM月dd日");
  String fn = "e:/db.dat";
  ObjectInputStream ois = new ObjectInputStream(new FileInputStream(fn));

  while (true) {
   try {
    Student stu = (Student) ois.readObject();
    System.out.println(stu.getName());
    System.out.println(stu.getAge());
    System.out.println(stu.getBirthday().toLocaleString());
    System.out.println("-----------------------------------------");

   } catch (Exception e) {
    break;
   }
  }

  // 对象输出流，主要将java的对象存储到文件
  Student s1 = new Student("李四", 22, sdf.parse("1985年5月20日"));
  ObjectOutputStream oos;
  if (new File(fn).length() < 1) {
   oos = new ObjectOutputStream(new FileOutputStream(fn, true));
  } else {
   oos = new My(new FileOutputStream(fn, true));
  }
  oos.writeObject(s1);
  oos.close();

 }
}

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ObjectInputStream与ObjectOutputStream类实现对象的存取