program5.txt

Java多线程机制的源码包括线程控制方法、多线程实现方法 、如何用接口来创建线程、输入输出流类、创建目录和删除文件

               raf2.close();
            } 
            catch(Exception e) 
            {
                System.err.println(e);
            }
        }
    }
} 

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4.5.3抽象流类

1．InputStream类
InputStream类的定义如下：
public abstract class InputStream extends Object 
{
    public InputStream();
    
    public abstract int read() throws IOException;
    public int read(byte b[]) throws IOException ;
    public int read(byte b[], int off, int len) throws IOException ;
    public long skip(long n) throws IOException ;
    public int available() throws IOException ;
    public void close() throws IOException ;
    public synchronized void mark(int readlimit) ;
    public synchronized void reset() throws IOException ;
    public boolean markSupported() ;
}

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2．OutputStream类
与输入流类相对应的另一个抽象类是OutputStream类，它定义了与输出操作有关的方法，其定义如下：
public abstract class OutputStream extends Object 
{
    public OutputStream();

    public abstract void write(int b) throws IOException;
    public void write(byte b[]) throws IOException;
    public void write(byte b[], int off, int len) throws IOException;
    public void flush() throws IOException;
    public void close() throws IOException;
}

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4.5.4文件输入输出流类

1．FileInputStream类
FileInputStream类提供从文件中读入数据的方法，其定义为：
public class FileInputStream extends InputStream 
{
    public FileInputStream(String name) throws FileNotFoundException;
    public FileInputStream(File file) throws FileNotFoundException;
    public FileInputStream(FileDescriptor fdObj);

    public int read() throws IOException;
    public int read(byte b[]) throws IOException;
    public int read(byte b[], int off, int len) throws IOException;
    public long skip(long n) throws IOException;
    // 使文件的读入指针向前或向后移动n个字节，其参数值相对于当前文件指针         
    public int available() throws IOException;
    //返回文件输入流中可供读入的字节数，实际上就是文件的长度。 
    public void close() throws IOException;
    public final FileDescriptor getFD() throws IOException;
    protected void finalize() throws IOException;
}

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例子：下面的程序说明FileInputStream类的使用方法。程序实现类似MS-DOS操作系统中type命令，用于显示文件内容。

 //Program Name: FileType.java
import java.io.*;
class FileType 
{
    public static void main(String[] args) 
    {
        if (args.length != 1) 
        {
            System.err.println("Usage: java FileType <input_file>");
            System.exit(-1);
        }
        File file = new File(args[0]);
        try 
        {
            FileInputStream in = new FileInputStream(file);
            int c;
            int i = 0;
            while ((c = in.read()) > -1) 
            {
                if((char)c == '\n')   i++; //统计行数
                System.out.print((char)c);
            }
            in.close();
            System.out.flush();
            System.out.println("\n\n\n----------------");
            System.out.println("File " + args[0] + " Lines: " + i);
        } 
        catch (FileNotFoundException e) 
        {
            System.err.println(file + " is not found");
        } 
        catch (IOException e) 
        {
            e.printStackTrace();
        }
    }
}
     
程序在生成FileInputStream对象时，用File对象给出文件名，虽然比用字符串给出文件名稍麻烦点，但这种方法使应用程序独立于平台，是一种良好的设计习惯。
程序在显示文件内容时使用了System.out.print()方法，而不是以前程序中常用的方法System.out.println()。
两者的区别是：println()执行时，立即把字符显示在屏幕上，并且每次调用println()方法，它总是在新的一行输出数据。print()执行时，并不立即显示数据，而把数据缓存在输出流中，直到遇到新行字符'\n'或执行了flush()方法后，才使字符显示在屏幕上。如果程序中使用println()，那么在屏幕上的显示情况就是一行一个字符，不是原来文件的行格式。

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2．FileOutputStream类
FileOutputStream类提供把数据写出到文件中的方法，其定义为：
public class FileOutputStream extends OutputStream 
{
    public FileOutputStream(String name) throws IOException;
    public FileOutputStream(String name, boolean append) throws IOException;
    public FileOutputStream(File file) throws IOException;
    public FileOutputStream(FileDescriptor fdObj);

    public void write(int b) throws IOException;
    public void write(byte b[]) throws IOException;
    public void write(byte b[], int off, int len) throws IOException;
    public void close() throws IOException;
    public final FileDescriptor getFD()  throws IOException;
}

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4.5.6其它输入输出流类

1．SequenceInputStream类
SequenceInputStream类可以将两个或几个输入流不露痕迹地接合在一起，生成一个长长的接合流，在读入数据时，它忽略前面几个输入流的结束符EOF，直到最后一个流的结束符EOF时，才完成流的输入，其定义如下：
public class SequenceInputStream extends InputStream 
{
    public SequenceInputStream(Enumeration e);
    //能够接合任意多个输入流
    public SequenceInputStream(InputStream s1, InputStream s2);
    只能接合两个输入流。

    public int read() throws IOException;
    public int read(byte buf[], int pos, int len) throws IOException;
    public int available() throws IOException;
    public void close() throws IOException;
}

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例子：下面程序把两个文件输入流接合成一个SequenceInputStream流，再写到一个文件中。
//Program Name: SeqTest.java
import java.io.*;
class SeqTest 
{
    public static void main(String[] args) 
    {
        FileInputStream fis1 = null;
        FileInputStream fis2 = null;
        FileOutputStream fos = null;
        SequenceInputStream  sis =null;
        int ch;
        if(args.length != 3) 
        { 
            System.out.println("Usage: java SeqTest <file1><file2><outfile>");
            System.exit(0);
        }
        try 
        {
            fis1 = new FileInputStream(new File(args[0]));
            fis2 = new FileInputStream(new File(args[1]));
            fos = new FileOutputStream(new File(args[2]));
        } 
        catch (IOException e) 
        {
            System.out.println("Cannot find file!");
            System.exit(-1);
        }
        sis = new SequenceInputStream(fis1, fis2);
        try 
        {
            while((ch = sis.read()) > -1)  fos.write(ch);
            fis1.close();
            fis2.close();
            sis.close();
        } 
        catch (IOException e) 
        {
            System.out.println(e);
            System.exit(-1);
        }
    }
}


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2．管道输入输出流类
Java使用了管道技术，用PipedInputStream类和PipedOutputStream类实现管道操作，这两个类必须同时使用，它们的定义分别为：
public class PipedInputStream extends InputStream 
{
    public PipedInputStream(PipedOutputStream src) throws IOException;
    public PipedInputStream();

    public synchronized int read()  throws IOException;
    public synchronized int read(byte b[], int off, int len)  throws IOException;
    public synchronized int available() throws IOException;
    public void close()  throws IOException;
    public void connect(PipedOutputStream src) throws IOException;
}

public class PipedOutputStream extends OutputStream 
{
    public PipedOutputStream(PipedInputStream snk)  throws IOException;
    public PipedOutputStream();

    public void write(int b)  throws IOException;
    public void write(byte b[], int off, int len) throws IOException;
    public synchronized void flush() throws IOException;
    public void close()  throws IOException;
    public void connect(PipedInputStream snk) throws IOException;
}


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例子：下面的程序使用两个线程：一个线程模拟数据采集，用Random类随机生成数值，另一个线程模拟数据处理，使用数据，计算其平均值。

//Program Name: PipeTest.java
import java.io.*;
import java.util.Random;
//数据处理
class RunningAverage extends Thread 
{
    private DataInputStream in;
    double total = 0;
    long count = 0;
    RunningAverage(InputStream i) 
    {
        in = new DataInputStream(i);
    }
    public void run() 
    {
        while (true) 
        {
            try 
            {
                double num = in.readDouble();
                total += num;
                count++;
                System.out.println(count + ": " + num + "\t avg = "+ total/count);
            } 
            catch (IOException e) 
            {
                e.printStackTrace();
            }
        }
    }
}
//数据采集
class NumberGenerator extends Thread 
{
    private DataOutputStream out;
    private Random gen = new Random();
    private final long RANGE = 1000;
    NumberGenerator(OutputStream o) 
    {
        out = new DataOutputStream(o);
    }
    public void run() 
    {
        while (true) 
        {
            try 
            {
                double num = gen.nextDouble() * RANGE;
                out.writeDouble(num);
                out.flush();
                sleep(500);
            } 
            catch (IOException e) 
            {
                e.printStackTrace();
            }  
            catch (InterruptedException e) 
            {
                e.printStackTrace();
            }
        }
    }
}
//主类
class PipeTest 
{
    public static void main(String[] args) 
    {
        try 
        {
            PipedOutputStream producer = new PipedOutputStream();
            PipedInputStream consumer = new PipedInputStream(producer);
            RunningAverage avg = new RunningAverage(consumer);
            NumberGenerator gen = new NumberGenerator(producer);
            gen.start();
            avg.start();
            try
            {
                Thread.sleep(5000);
            }
            catch (InterruptedException e) {}
            gen.stop();
            avg.stop();
            producer.close();
            consumer.close();
        } 
        catch (IOException e) 
        {
            e.printStackTrace();
        }
    }
}

程序用PipedOutputStream()生成管道输出流producer，用PipedInputStream(producer)生成管道输入流consumer，同时实现了两个管道的连接。
程序中的两个类RunningAverage和NumberGenerator，都是Thread类的子类，是两个不同的线程。前一个类生成数据，用管道输出这些数据，后一个类从输入管道接收数据，然后计算平均值。main()在启动了这两个线程工作后，睡眠5秒钟，然后stop()两个线程，再close()管道输入输出流而结束程序。

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5.3网络编程

5.3.1 InetAddress
 
例1：TestAdd.java
import java.net.*; 
import java.io.*;
public class TestAdd 
{ 
    public static void main(String args[])
    {
        try
        {
            if(args.length==1)
            {
                InetAddress ipa=InetAddress.getByName(args[0]);
                System.out.println("Host name:"+ipa.getHostName());
                //获取主机名
                System.out.println("Host Address:"+ipa.getHostAddress());
                //获取IP地址
                System.out.println("Host IP Address:"+ipa.toString());
                //获取主机名/IP地址
                System.out.println("Local Host:"+InetAddress.getLocalHost());
                String s=ipa.isMulticastAddress()? " Yes" : " No";
                System.out.println("is MuticastAddress:"+s);
                byte[] addr=ipa.getAddress();
                System.out.println("Use getAddress():"+addr[0]+"."+addr[1]+"."+addr[2]+"."+addr[3]);
                System.out.println("Converted getAddress():"+(addr[0]&0XFF)+"."+(addr[1]&0XFF)+"."+(addr[2]&0XFF)+"."+(addr[3]&0XFF));
            }
            else