Java IO 流 -- 数据流和对象流 DataOutputStream ObjectOutputStream

DataOutputStream 和 ObjectOutputStream的共同点是：

1、写出后读取

2、读取顺序和写出一致

数据流操作：

// 写入
		ByteArrayOutputStream baos = new ByteArrayOutputStream();
		DataOutputStream dos = new DataOutputStream(new BufferedOutputStream(baos));
		dos.writeUTF("编码辛酸泪");
		dos.writeInt(18);
		dos.writeBoolean(false);
		dos.writeChar('a');
		dos.flush();
		byte[] datas = baos.toByteArray();
		System.out.println(datas.length);

		// 写出
		ByteArrayInputStream bais = new ByteArrayInputStream(datas);
		DataInputStream dis = new DataInputStream(new BufferedInputStream(bais));
		String msg = dis.readUTF();
		int age = dis.readInt();
		boolean flag = dis.readBoolean();
		char ch = dis.readChar();
		System.out.println(ch);

对象流操作：

对象的写入写入又叫序列化和方序列化，需要注意的是，并不是所有的对象都可以序列化，如果要对对象进行序列化，需要实现 Serializable 接口，如果不想让对象中某个属性序列化，可以使用 transient 关键字标识

比如我们自己定义一个类：

class Employee implements Serializable{
	private transient String name;
	private double salary;
	public Employee() {
	}
	public Employee(String name, double salary) {
		super();
		this.name = name;
		this.salary = salary;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public double getSalary() {
		return salary;
	}
	public void setSalary(double salary) {
		this.salary = salary;
	}

}

序列化到字节数组：

// 写出--> 序列化
		ByteArrayOutputStream baos = new ByteArrayOutputStream();
		ObjectOutputStream oos = new ObjectOutputStream(new BufferedOutputStream(baos));
		// 操作数据类型
		oos.writeUTF("编码辛酸泪");
		oos.writeInt(18);
		oos.writeBoolean(false);
		oos.writeChar('a');

		// 操作对象
		oos.writeObject("谁解其中味");
		oos.writeObject(new Date());
		oos.writeObject(new Employee("马云", 400));
		oos.flush();
		byte[] datas = baos.toByteArray();
		oos.close();

		// 读取--> 反序列化
		ByteArrayInputStream bais = new ByteArrayInputStream(datas);
		ObjectInputStream ois = new ObjectInputStream(new BufferedInputStream(bais));

		String msg = ois.readUTF();
		int age = ois.readInt();
		boolean flag = ois.readBoolean();
		char ch = ois.readChar();
		System.out.println(age);

		// 对象还原
		Object str = ois.readObject();
		Object date = ois.readObject();
		Object emp = ois.readObject();
		if(str instanceof String) {
			String strObj = (String) str;
			System.out.println(strObj);
		}

		if(date instanceof Date) {
			Date dateObj = (Date) date;
			System.out.println(dateObj);
		}

		if(emp instanceof Employee) {
			Employee empObj = (Employee) emp;
			System.out.println(empObj.getName() + "-->" + empObj.getSalary());
		}

		ois.close();
	}

序列化到文件：

// 写出--> 序列化
		ObjectOutputStream oos = new ObjectOutputStream(
				new BufferedOutputStream(new FileOutputStream("obj.ser")));
		// 操作数据类型
		oos.writeUTF("编码辛酸泪");
		oos.writeInt(18);
		oos.writeBoolean(false);
		oos.writeChar('a');

		// 操作对象
		oos.writeObject("谁解其中味");
		oos.writeObject(new Date());
		oos.writeObject(new Employee("马云", 400));
		oos.flush();
		oos.close();

		// 读取--> 反序列化
		ObjectInputStream ois = new ObjectInputStream(
				new BufferedInputStream(new FileInputStream("obj.ser")));

		String msg = ois.readUTF();
		int age = ois.readInt();
		boolean flag = ois.readBoolean();
		char ch = ois.readChar();
		System.out.println(age);

		// 对象还原
		Object str = ois.readObject();
		Object date = ois.readObject();
		Object emp = ois.readObject();
		if(str instanceof String) {
			String strObj = (String) str;
			System.out.println(strObj);
		}

		if(date instanceof Date) {
			Date dateObj = (Date) date;
			System.out.println(dateObj);
		}

		if(emp instanceof Employee) {
			Employee empObj = (Employee) emp;
			System.out.println(empObj.getName() + "-->" + empObj.getSalary());
		}

		ois.close();