java中IO对list的读写操作

1.自定义类实现serializable接口

package day20;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;

public class TestIO {

	@SuppressWarnings("unchecked")
	public static void main(String[] args) throws Exception {
		// TODO Auto-generated method stub//	
		Student s1 = new Student("zhang3",12);
		Student s2 = new Student("li4",15);
		Student s3 = new Student("zhao6",20);
			
		List<Student> list = new ArrayList<Student>();
		list.add(s1);
		list.add(s2);
		list.add(s3);
		//把对象写入文件
		FileOutputStream fos = new FileOutputStream("Student.txt");
		ObjectOutputStream out = new ObjectOutputStream(fos);
		//把list写入文件
		out.writeObject(list);
		out.close();
		//从文件中读取对象
		FileInputStream fis = new FileInputStream("Student.txt");
		ObjectInputStream in = new ObjectInputStream(fis);
		List<Student> list1 = new ArrayList<Student>();
		try {
			//把读到的内容放在一个list中
			list1 = (ArrayList<Student>)in.readObject();
			System.out.println(list1);
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		in.close();
	}

}
class Student implements Serializable{
	private static final long serialVersionUID = 42L;
	String name;
//	transient int age;  //transient 修饰属性时 该属性为临时属性 不参与对象序列化
	int age;
	public Student() {
		System.out.println("haha");
	}
	public Student(String name,int age) {
		this.name = name;
		this.age = age;
	}
	@Override
	public String toString() {
		return "name: " + name + "\t" + "age: " + age;
	}
}

2.自定义类实现Externalizable接口 

     使用ObjectOutputStream 把list写入文件中

      使用ObjectInputStream 从文件中读取文件

package day20;
import java.io.Externalizable;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInput;
import java.io.ObjectInputStream;
import java.io.ObjectOutput;
import java.io.ObjectOutputStream;
import java.util.ArrayList;
import java.util.List;
//自定义序列化
public class TestList {

	@SuppressWarnings("unchecked")
	public static void main(String[] args) throws Exception{
		// TODO Auto-generated method stub
		//创建两个对象
		Animal t1 = new Animal("zhang3",13,"男");
		Animal t2 = new Animal("li4",20,"女");
		//把对象写入list中  并指定list的泛型
		List<Animal> list = new ArrayList<Animal>();
		list.add(t1);
		list.add(t2);
		
		//文件输出流
		FileOutputStream fos = new FileOutputStream("Animal.dat");
		//过滤流
		ObjectOutputStream out = new ObjectOutputStream(fos);
		//把list写入文件中
		out.writeObject(list);
		//关闭流
		out.close();
		//文件输入流
		FileInputStream fis = new FileInputStream("Animal.dat");
		//过滤流
		ObjectInputStream in = new ObjectInputStream(fis);
		//创建一个list1用于接收从文件中读取的list对象
		List<Animal> list1 = new ArrayList<Animal>();
		try {
			//读取list   readObject读取出来的是Object类型  需要强转为ArrayList<Student>类型
			list1 = (ArrayList<Animal>)in.readObject();
			System.out.println(list1.get(0));
		} catch (Exception e) {
		}
		in.close();
	}

}

class Animal implements Externalizable{  //实现Externalizable接口  里面有两个方法需要实现
	String name;
	int age;
	String sex;
	public Animal() {}
	public Animal(String name,int age,String sex) {
		this.name = name;
		this.age = age;
		this.sex = sex;
	}
	@Override
	public String toString() {
		return "Animal [name=" + name + ", age=" + age + "]";
	}
	//往文件中写数据  传入out流  这个流不需要close  实现对象的序列化
	@Override
	public void writeExternal(ObjectOutput out) throws IOException {
		// TODO Auto-generated method stub
		out.writeUTF(name);//把name属性写进文件
		out.writeInt(age);//把name属性写进文件
		out.writeUTF(sex);//把name属性写进文件
	}
	//从文件中读取数据  实现对象的反序列化
	@Override
	public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException {
		// TODO Auto-generated method stub
		name = in.readUTF();
		age = in.readInt();
		sex = in.readUTF();
	}
	
}