乱码是怎么回事

import java.io.Serializable;

public class Product implements Serializable{
	private String ID;//产品ID
	private String name;//产品名称
	private String categories;//产品属性
	private double price;//产品价格
	public Product(String ID,String name,String categories,double price){
		this.setID(ID);
		this.setName(name);
		this.setCategories(categories);
		this.setPrice(price);
	}
	public String getID() {
		return ID;
	}
	public void setID(String iD) {
		ID = iD;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getCategories() {
		return categories;
	}
	public void setCategories(String categories) {
		this.categories = categories;
	}
	public double getPrice() {
		return price;
	}
	public void setPrice(double price) {
		this.price = price;
	}
	public String toString(){
		return "产品ID:"+this.getID()+"/n"+"产品名称："+this.getName()+"/n"+"产品属性："+this.getCategories()+"/n"+"产品价格："+this.getPrice();
	}
}

import java.io.BufferedOutputStream;
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.io.OutputStreamWriter;

public class ProductTest {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Product product1=new Product("123","iphone","telephone",4888.0);
		Product product2=new Product("234","ipad","computer",5088.0);
		Product product3=new Product("345","macbook","computer",10688.0);
		Product product4=new Product("256","iwatch","watch",4799.0);
		System.out.println("apple系列产品信息：");
		try {
			FileOutputStream fos=new FileOutputStream("product.txt");
			ObjectOutputStream oos=new ObjectOutputStream(fos);
			oos.writeObject(product1);
			oos.writeObject(product2);
			oos.writeObject(product3);
			oos.writeObject(product4);
			oos.flush();
			
			FileInputStream fis=new FileInputStream("product.txt");
			ObjectInputStream ois=new ObjectInputStream(fis);
				System.out.println((Product)ois.readObject());
				fos.close();
				oos.close();
				fis.close();
				ois.close();
			
			
		} catch (FileNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}catch (ClassNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	catch(IOException e){
			e.printStackTrace();
		}
	}

}