第21天-01-IO流(对象的序列化)
ObjectInputStream与ObjectOutputStream
- 被操作的对象需要实现Serializable接口(标记接口)
- 非必须, 但强烈建议所有可序列化类都显式声明serialVersionUID
package bxd; import java.io.*; public class ObjectStreamDemo { public static void readObj() throws Exception { ObjectInputStream ois = new ObjectInputStream(new FileInputStream("Person.object")); Person person = (Person) ois.readObject(); System.out.println(person); ois.close(); } public static void writeObj() throws Exception { ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("Person.object")); oos.writeObject(new Person("lily", 39, "us")); oos.close(); } public static void main(String[] args) throws Exception { // writeObj(); readObj(); } } /* 输出lily:0:cn, 因为age不会被序列化(使用初始值0), 静态变量country也不会被序列化(使用初始值cn). */ class Person implements Serializable { public static final long serialVersionUID = 42L; // 强烈建议所有可序列化类都显式声明serialVersionUID private String name; transient int age; // 如果某个实例变量不需要被序列化, 可以使用transient修饰 static String country = "cn"; // 序列化行为只针对Java堆(heap), 而静态变量不存在于heap. Person(String name, int age, String country) { this.name = name; this.age = age; this.country = country; } public String toString() { return name + ":" + age + ":" + country; } }
第21天-02-IO流(管道流)
PipedInputStream和PipedOutputStream
- 输入和输出可以直接进行连接, 通常结合线程使用.
- 不建议对这两个对象尝试使用单个线程, 因为这样可能发生线程死锁
package bxd; import java.io.*; public class PipedStreamDemo { public static void main(String[] args) throws IOException { PipedInputStream pipedInputStream = new PipedInputStream(); PipedOutputStream pipedOutputStream = new PipedOutputStream(); // 只要往pipedOutputStream写入的内容, 就可以从pipedInputStream读到 pipedInputStream.connect(pipedOutputStream); Read read = new Read(pipedInputStream); Write write = new Write(pipedOutputStream); new Thread(read).start(); new Thread(write).start(); } } class Write implements Runnable { private PipedOutputStream out; public Write(PipedOutputStream out) { this.out = out; } @Override public void run() { try { System.out.println("开始执行PipedOutputStream操作: "); BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in)); String line = null; while ((line = bufferedReader.readLine()) != null) { if ("over".equals(line)) break; out.write(line.getBytes()); out.write(System.lineSeparator().getBytes()); } bufferedReader.close(); out.close(); } catch (IOException e) { e.printStackTrace(); } } } class Read implements Runnable { private PipedInputStream in; public Read(PipedInputStream in) { this.in = in; } @Override public void run() { try { System.out.println("开始执行PipedInputStream操作: "); BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(new FileOutputStream("读取到的内容.txt")); byte[] buf = new byte[1024]; int len = 0; while ((len = in.read(buf)) != -1) { bufferedOutputStream.write(buf, 0, len); } bufferedOutputStream.close(); in.close(); } catch (IOException e) { e.printStackTrace(); } } }