Java文件与io——打印流和对象流

打印流的主要功能是用于输出，在整个IO包中打印流分为两种类型：

字节打印流：PrintStream

字符打印流：PrintWriter

打印流可以很方便的进行输出

public class PrintStreamDemo {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        byteStreamOut();
        charStreamOut();
    }
    //PrintStream
    public static void byteStreamOut(){
        try {
            OutputStream out=new FileOutputStream("G:\\hhb.txt");
            BufferedOutputStream bos=new BufferedOutputStream(out);
            PrintStream ps=new PrintStream(bos);//更加方便的输出
            //bos.write("hhhhh".getBytes());
            ps.println(123);
            ps.close();
            bos.close();
            out.close();
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        
    }
    //PrintWriter
    public static void charStreamOut(){
        try {
            Writer w=new FileWriter("G:\\hhh.txt");
            BufferedWriter bw=new BufferedWriter(w);
            PrintWriter pw=new PrintWriter(bw);
            pw.println(343);
            pw.println("lll");
            //bw.write("我爱你！");
            pw.close();
            bw.close();
            w.close();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

}

对象流

对象序列化

对象序列化就是指将一个对象转化为二进制的byte流。

两种情况：

将对象保存在文件上的操作称为对象的序列化操作

将对象从文件之中恢复称为反序列化的操作

使用ObjectOutputStream类实现对象的序列化，使用ObjectInputStream类实现反序列。

被序列化的对象所在的类必须实现java.io.Serializable接口

public class Cat implements Serializable{
    private String name;
    private int age;
    private transient String color;//关键字transient，表示不用序列化
    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 Cat(String name, int age) {
        super();
        this.name = name;
        this.age = age;
    }
    @Override
    public String toString() {
        return "Cat [name=" + name + ", age=" + age + "]";
    }
    public Cat() {
        super();
        // TODO Auto-generated constructor stub
    }
    
}

public class ObjectStreamDemo {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        objectOut();
        objectIn();
    }
    //实现对象的序列化
    public static void objectOut(){
        Cat cat=new Cat("mimi",3);
        try {
            OutputStream out=new FileOutputStream("G://555.kds");
            ObjectOutputStream oos=new ObjectOutputStream(out);
            oos.writeObject(cat);
            oos.close();
            out.close();
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    //实现反序列化
    public static void objectIn(){
        try {
            InputStream in=new FileInputStream("G://555.kds");
            ObjectInputStream ois=new ObjectInputStream(in);
            Cat cat=(Cat)ois.readObject();
            System.out.println(cat);
            ois.close();
            in.close();
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}