PipedInputStream/PipedOutputStream

PipedInputStream和PipedOutputStream分別是管道輸入流和管道輸出流.

它們的做用是讓多線程之間能夠經過管道進行通信,在使用管道通訊時,必須將PipedInputStream和PipedOutputStream配合使用.

使用管道通訊時,大體流程是:線程A向PipedOutputStream中寫入數據,這些數據會自動的發送到對應的pipedInputStream中進行緩存,此時,線程B經過讀取PipedInputStream中的數據,就能夠實現線程通訊了.

實驗一:發送簡短的消息

Sender.java(發送消息)

public class Sender extends Thread {
    private PipedOutputStream pos = new PipedOutputStream();

    public Sender(PipedOutputStream pos) {
    this.pos = pos;
    }

    @Override
    public void run() {
         sendShortMessage();
    }

    // 發送簡單的消息
    public void sendShortMessage() {
    try {
        pos.write("你好啊!".getBytes());
    } catch (IOException e) {
        e.printStackTrace();
    } finally {
        try {
        pos.close();
        } catch (IOException e) {
        e.printStackTrace();
        }
    }
    }
}

Reciver.java(接受消息)

public class Reciver extends Thread {
    private PipedInputStream pis = new PipedInputStream();

    public Reciver(PipedInputStream pis) {
    this.pis = pis;
    }

    @Override
    public void run() {
    byte[] buf = new byte[2048];
    try {
        pis.read(buf);
        pis.close();
    } catch (IOException e) {
        e.printStackTrace();
    }
    System.out.println("Reciver :" + new String(buf));
    }
}

PipedTest.java

public class PipedTest {
    public static void main(String[] args) throws IOException {
    PipedOutputStream pipedOutputStream = new PipedOutputStream();
    PipedInputStream pipedInputStream = new PipedInputStream();
    Sender sender = new Sender(pipedOutputStream);
    Reciver reciver = new Reciver(pipedInputStream);
    pipedInputStream.connect(pipedOutputStream);
    sender.start();
    reciver.start();
    }
}
//Reciver :你好啊!

實驗一很好理解:

pipedInputStream.connect(pipedOutputStream);方法把PipedOutPutStream和PipedInputStream關聯了起來.
Sender經過write()方法,向PipedInputStream中寫入"你好啊!",查看PipedOutputStream的writer()方法可知,實際上是調用了PipedinputStream的receive()方法,繼續查看該方法可知,PipedinputStream的

receive()方法,其實就是把數據保存到本身的byte buffer[]數組中,並且其數組的默認大小爲1024.
Reciver經過read()方法,從本身的byte buffer[]數組中讀取數據.

實驗二:發送較長的消息

 Sender.java(發送消息)

public class Sender extends Thread {
    private PipedOutputStream pos = new PipedOutputStream();

    public Sender(PipedOutputStream pos) {
    this.pos = pos;
    }

    @Override
    public void run() {
    sendShortMessage();
    }

    // 發送較長的消息
    public void sendLongMessage() {
    StringBuilder sb = new StringBuilder();
    // 總共長度是1020個字節
    for (int i = 0; i < 102; i++) {
        sb.append("0123456789");
    }
    // 再寫入26個字節。
    sb.append("abcdefghijklmnopqrstuvwxyz");
    // str的總長度是1020+26=1046個字節
    String str = sb.toString();
    try {
        pos.write(str.getBytes());
    } catch (IOException e) {
        e.printStackTrace();
    } finally {
        try {
        pos.close();
        } catch (IOException e) {
        e.printStackTrace();
        }
    }
    }
}

Reciver.java(接受消息)

 

public class Reciver extends Thread {
    private PipedInputStream pis = new PipedInputStream();

    public Reciver(PipedInputStream pis) {
    this.pis = pis;
    }

    @Override
    public void run() {
    byte[] buf = new byte[2048];
    try {
        pis.read(buf);
        pis.close();
    } catch (IOException e) {
        e.printStackTrace();
    }
    System.out.println("Reciver :" + new String(buf));
    }
}

 PipedTest.java

public class PipedTest {
    public static void main(String[] args) throws IOException {
    PipedOutputStream pipedOutputStream = new PipedOutputStream();
    PipedInputStream pipedInputStream = new PipedInputStream();
    Sender sender = new Sender(pipedOutputStream);
    Reciver reciver = new Reciver(pipedInputStream);
    pipedInputStream.connect(pipedOutputStream);
    sender.start();
    reciver.start();
    }
}

 實驗二的運行結果爲:Reciver :012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789abcd

發現收到的數據少了"efghijklmnopqrstuvwxyz",爲何打印出來的數據正好是1024長度.其實上面咱們已經說過了,PipedInputStream的byte [] buffer數組的默認長度只有1024,因此上面的輸出是這樣的.那怎麼改才能輸出所有內容的?

咱們修改Reciver.java

public class Reciver extends Thread {
    private PipedInputStream pis = new PipedInputStream();

    public Reciver(PipedInputStream pis) {
    this.pis = pis;
    }

    @Override
    public void run() {
    reciverLongMessage();
    }

    public void reciverLongMessage() {
    while (true) {
        byte[] buf = new byte[1024];
        int len;
        try {
        len = pis.read(buf);
        if (len > 0) {
            System.out.println(new String(buf, 0, len));
        } else {
            break;
        }
        } catch (IOException e) {
        try {
            pis.close();
        } catch (IOException e2) {
            e2.printStackTrace();
        }
        }
    }
    }
}

 這樣就能夠正確輸出結果啦!