多线程学习--管道/交叉线程

超、凢脫俗 2024-02-19 14:38 58阅读 0赞

**管道进行线程通信-字节流：**

管道进行线程通信使用的pipeStream流。一个线程发送数据到管道，另一个线程从输入管道中读取数据。

JDK提供了4个类来世线程间可以进行通信：

字节流：PipedInputStream与PipedOutputStream

字符流：PipedWriter,PipedReader

字节流案例：

class WriteData {
        public void writeMethod(PipedOutputStream out) {
            try {
                System.out.println("write  :");
                for (int i = 0; i < 300; i++) {
                    String outData = "" + (i + 1);
                    out.write(outData.getBytes());
                    System.out.print(outData);
                }
                System.out.println();
                out.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
    
        }
    }
    class ReadData {
        public void readMethod(PipedInputStream input) {
            try {
                System.out.println("read   :");
                byte[] bytes = new byte[20];
                int readLength = input.read(bytes);
                while (readLength != -1) {
                    String newData = new String(bytes, 0, readLength);
                    System.out.print("read   :"+newData);
                    readLength = input.read(bytes);
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
    public class RunpipeInputOutput {
        public static void main(String[] args) {
            try {
                WriteData writeData = new WriteData();
                ReadData readData = new ReadData();
                PipedInputStream inputStream = new PipedInputStream();
                PipedOutputStream outputStream = new PipedOutputStream();
                inputStream.connect(outputStream);
                //outputStream.connect(inputStream);
    
                new Thread(()->{
                    readData.readMethod(inputStream);
                },"输入").start();
    
             
                Thread.sleep(2000);
    
                new Thread(()->{
                    writeData.writeMethod(outputStream);
                },"读取").start();
             
    
            } catch (IOException e) {
                e.printStackTrace();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

结果：

read   :
    write  :
    123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495
    read   :12345678910111213141read   :51617181920212223242read   :52627282930313233343read

说明：首先是读取线程启动，由于当时没有数据被写入，所以线程阻塞在 int readLength = input.read(bytes);。直到有数据被写入，才继续向下运行。

字符流案例：

class WriteData {
        public void writeMethod(PipedWriter out) {
            try {
                System.out.println("write  :");
                for (int i = 0; i < 300; i++) {
                    String outData = "" + (i + 1);
                    out.write(outData);
                    System.out.print(outData);
                }
                System.out.println();
                out.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
    
        }
    }
    class ReadData {
        public void readMethod(PipedReader input) {
            try {
                System.out.println("read   :");
                char[] bytes = new char[20];
                int readLength = input.read(bytes);
                while (readLength != -1) {
                    String newData = new String(bytes, 0, readLength);
                    System.out.print("read   :"+newData);
                    readLength = input.read(bytes);
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
    public class Run12_pipeInputOutput {
        public static void main(String[] args) {
            try {
                WriteData writeData = new WriteData();
                ReadData readData = new ReadData();
                PipedWriter pipedWriter = new PipedWriter();
                PipedReader pipedReader = new PipedReader();
                pipedWriter.connect(pipedReader);
                //outputStream.connect(inputStream);
    
                new Thread(()->{
                    readData.readMethod(pipedReader);
                },"输入").start();
    
                Thread.sleep(2000);
    
                new Thread(()->{
                    writeData.writeMethod(pipedWriter);
                },"读取").start();
    
            } catch (IOException e) {
                e.printStackTrace();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

线程交叉运行： 关键点在于设置标识。多个线程可见。

class DBTools {
        volatile private boolean prevIsA = false;
    
        synchronized public void backupA() {
            try {
                while (prevIsA == true) {
                    wait();
                }
                for (int i = 0; i < 5; i++) {
                    System.out.println("★★★★★");
                }
                prevIsA = true;
                notifyAll();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    
        synchronized public void backupB() {
            try {
                while (prevIsA == false) {
                    wait();
                }
                for (int i = 0; i < 5; i++) {
                    System.out.println("☆☆☆☆☆");
                }
                prevIsA = false;
                notifyAll();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
    public class RunTest {
        public static void main(String[] args) {
            DBTools dbTools = new DBTools();
            for (int i = 0; i < 20; i++) {
    
                new Thread(()->{
                    dbTools.backupB();
                },"线程A").start();
    
                new Thread(()->{
                    dbTools.backupA();
                },"线程B").start();
            }
        }
    }

运行结果:

★★★★★
    ★★★★★
    ★★★★★
    ★★★★★
    ★★★★★
    ☆☆☆☆☆
    ☆☆☆☆☆
    ☆☆☆☆☆
    ☆☆☆☆☆
    ☆☆☆☆☆
    ★★★★★
    ★★★★★
    ★★★★★
    ★★★★★
    ★★★★★
    ☆☆☆☆☆
    ☆☆☆☆☆
    ☆☆☆☆☆
    ☆☆☆☆☆
    ☆☆☆☆☆
    .........