1.1 Overview
The ObjectInputStream used to read objects from the stream is
called deserialization stream, and the input stream is used to read objects from a file.
ObjectOutputStream is called serialization stream, and the output stream is used to write objects into files.
Features: used to manipulate objects. Objects can be written to and read from files.
package com.itheima_07;
/*
* 对象操作流：可以用于读写任意类型的对象
* ObjectOutputStream
* writeObject
* ObjectOutputStream(OutputStream out)
* ObjectInputStream
* readObject
* ObjectInputStream(InputStream in)
*
* 注意：
* 使用对象输出流写出对象，只能使用对象输入流来读取对象
* 只能将支持 java.io.Serializable 接口的对象写入流中
*
*/
public class ObjectOutputStreamDemo2 {
public static void main(String[] args) {
}
}1.2 Using serialized streams to read and write objects
package com.itheima_07;
import java.io.Serializable;
public class Student implements Serializable {
/**
*
*/
String name;
int age;
public Student(String name,int age) {
this.name = name;
this.age = age;
}
@Override
public String toString() {
return "Student [name=" + name + ", age=" + age +"]";
}
}
package com.itheima_07;
import java.io.EOFException;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
/*
* 使用对象输出流和读对象输入流写对象
* Exception in thread "main" java.io.NotSerializableException: com.itheima_07.Student
* Serializable:序列号，是一个标识接口，只起标识作用，没有方法
* 当一个类的对象需要IO流进行读写的时候，这个类必须实现该接口
*
* Exception in thread "main" java.io.EOFException:当输入过程中意外到达文件或流的末尾时，抛出此异常。
*
*/
public class ObjectOutputStreamDemo {
public static void main(String[] args) throws IOException, ClassNotFoundException {
//method();
//创建对象输入流的对象
ObjectInputStream ois = new ObjectInputStream(new FileInputStream("a.txt"));
//读取对象
/*Object obj = ois.readObject();
System.out.println(obj);
Object obj2 = ois.readObject();
System.out.println(obj2);
Object obj3 = ois.readObject();
System.out.println(obj3);*/
try {
while(true) {
Object obj = ois.readObject();
System.out.println(obj);
}
} catch(EOFException e) {
System.out.println("读到了文件的末尾");
}
//释放资源
ois.close();
}
private static void method() throws IOException, FileNotFoundException {
//创建对象输出流的对象
//FileOutputStream fos = new FileOutputStream("a.txt");
//ObjectOutputStream oos = new ObjectOutputStream(fos);
ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("a.txt"));
//创建学生对象
Student s = new Student("zhangsan",18);
Student s2 = new Student("lisi",19);
//写出学生对象
oos.writeObject(s);
oos.writeObject(s2);
//释放资源
oos.close();
}
}1.2.1 Case code six:
package com.itheima_02;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
/*
* 使用字符流复制文本文件
*
* 数据源 IODemo.java
* 目的地 d:\\IODemo.java
*
*/
public class FileCopyDemo {
public static void main(String[] args) throws IOException {
//创建字符输入流对象
FileReader fr = new FileReader("IODemo.java");
//创建字符输出流对象
FileWriter fw = new FileWriter("d:\\IODemo.java");
//一次读写一个字符
/*int ch;
while((ch = fr.read()) != -1) {
fw.write(ch);
fw.flush();
}*/
//一次读写一个字符数组
int len;//用于存储读到的字符个数
char[] chs = new char[1024];
while((len = fr.read(chs)) != -1) {
fw.write(chs,0,len);
fw.flush();
}
//释放资源
fw.close();
fr.close();
}
}1.3 Solve the problem that the object input stream is abnormal when reading the object 1.3.1 Case code 7:
package com.itheima_07;
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.util.ArrayList;
/*
* 解决对象输入流读取对象出现异常的问题
*
*/
public class ObjectOutputStreamDemo3 {
public static void main(String[] args) throws IOException, ClassNotFoundException {
//method();
//创建对象输入流的对象
ObjectInputStream ois = new ObjectInputStream(new FileInputStream("b.txt"));
//读取数据
Object obj = ois.readObject();
//System.out.println(obj);
//向下转型，获取具体的子类对象
ArrayList<Student> list = (ArrayList<Student>) obj;
for (Student student : list) {
System.out.println(student);
}
//释放资源
ois.close();
}
private static void method() throws IOException, FileNotFoundException {
//创建对象输出流的对象
ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("b.txt"));
//创建集合对象
ArrayList<Student> list = new ArrayList<Student>();
//添加学生对象
list.add(new Student("wangwu",30));
list.add(new Student("zhaoliu",28));
//写出集合对象
oos.writeObject(list);
//释放资源
oos.close();
}
}1.4 Solve the problem of inconsistent versions of read and write objects
1.4.1 Case code 8:
package com.itheima_07;
import java.io.Serializable;
public class Student implements Serializable {
/**
*
*/
private static final long serialVersionUID = 6361890890437825953L;
String name;
int age;
String gender;
public Student(String name,int age) {
this.name = name;
this.age = age;
}
@Override
public String toString() {
return "Student [name=" + name + ", age=" + age + ", gender=" + gender + "]";
}
}package com.itheima_07;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
/*
* 解决对实现序列化接口出现的×××警告问题
* Exception in thread "main" java.io.InvalidClassException
* 当 Serialization 运行时检测到某个类具有以下问题之一时，抛出此异常。
该类的序列版本号与从流中读取的类描述符的版本号不匹配
该类包含未知数据类型
该类没有可访问的无参数构造方法
*
*/
public class ObjectOutputStreamDemo4 {
public static void main(String[] args) throws IOException, ClassNotFoundException {
//method();
method2();
}
//读取学生对象
private static void method2() throws IOException, FileNotFoundException, ClassNotFoundException {
//创建对象输入流的对象