文件下载

import java.io.*;
/**
*   文件下载类
**/
public class DownloadFile {
   
    public static void main( String[] args ) {
        // 获取屏幕输入
        BufferedReader r = null;
        try {
            r = new BufferedReader( new InputStreamReader( System.in ) );
            String s = "";
            System.out.println( "请输入需要下载的文件路径：" );
            while ( ( s = r.readLine() ) != null ) {
                // 判断文件路径是否已经输入过
                if ( DownloadConfig.getInstance().dFile == null ) {
                    // 文件路径未输入的场合
                    if ( !"".equals(s) ) {
                        // 构造文件
                        File f = new File( s );
                        if ( f.exists() && f.isFile() ) {
                            DownloadConfig.getInstance().dFile = f;
                            System.out.println("请输入下载的线程数量：");
                        } else {
                            System.out.println("下载的文件不存在,请重新输入：");
                        }
                    } else {
                        System.out.println("文件路径不能为空,请重新输入：");
                    }
                } else {
                    // 文件路径已经输入的场合
                    // 获取下载线程的数量
                    try {
                       
                        DownloadConfig.getInstance().threadCount = Integer.parseInt(s);
                        DownloadConfig.getInstance().threadPercent = new double[DownloadConfig.getInstance().threadCount];
                        File f = new File( DownloadConfig.SAVE_PATH );
                        if ( !f.exists() ) {
                            f.mkdirs();
                        }
                        // 执行下载操作
                        download();
                        break;
                    } catch ( NumberFormatException e ) {
                        System.out.println("输入的数量不合法，请重新输入：");
                    }
                }
            }
        } catch ( IOException e ) {
            System.out.println("屏幕输入异常");
        } finally {
            if ( r != null ) {
                try {
                    r.close();
                } catch ( IOException e ) {
                    r = null;
                }
            }
        }
    }
    public static void download() {
        // 分割文件
        BufferedInputStream buffIn = null;
        try {
            buffIn = new BufferedInputStream( new FileInputStream( DownloadConfig.getInstance().dFile ) );
            // 获取下载文件的大小
            int fileSize = buffIn.available();
            // 获取每个线程下载的最小字节数
            int cnt = fileSize / DownloadConfig.getInstance().threadCount;
            // 整除标志
            boolean flg = true;
           
            if ( fileSize % DownloadConfig.getInstance().threadCount != 0 ) {
                flg = false;
            }
            // 构造下载线程
            DownloadProcess[] dps = new DownloadProcess[DownloadConfig.getInstance().threadCount];
           
            // 启动监听器
            new DownloadListener().start();
           
            for ( int i = 0; i < dps.length; i++ ) {
                if ( i != dps.length - 1 ) {
                    dps[i] = new DownloadProcess( i, cnt, cnt );
                } else {
                    if ( flg ) {
                        dps[i] = new DownloadProcess( i, cnt, cnt );
                    } else {
                        dps[i] = new DownloadProcess( i, cnt, fileSize - (DownloadConfig.getInstance().threadCount - 1)*cnt );
                    }
                }
                dps[i].start();
            }
        } catch ( IOException e ) {
            System.out.println("输入输出异常");
        } finally {
            if ( buffIn != null ) {
                try {
                    buffIn.close();
                } catch ( IOException e ) {
                    buffIn = null;
                }
            }
        }
    }
}
/**
*
*/
class DownloadListener extends Thread {
    public void run() {
        BufferedInputStream buffIn = null;
        BufferedOutputStream buffOut = null;
        try {
            // 监听下载进度
           
            // 下载完成的线程数量
            int count = 0;
            while ( count != DownloadConfig.getInstance().threadPercent.length ) {
                count = 0;
                System.out.println();
                System.out.println("***********文件下载监视中***********");
                for ( int i = 0; i < DownloadConfig.getInstance().threadPercent.length; i++ ) {
                    int percent = (int)(DownloadConfig.getInstance().threadPercent[i]*100);
                    System.out.println("第"+i+"个线程下载的进度是：" + percent + "%");
                    if ( percent == 100 ) {
                        count++;
                    }
                }
                System.out.println("************************************");
               
                sleep( 50 );
            }
           
            // 合并文件
            buffOut = new BufferedOutputStream( new FileOutputStream( DownloadConfig.SAVE_PATH + DownloadConfig.getInstance().dFile.getName(), true ) );
           
            for ( int i = 0; i < DownloadConfig.getInstance().threadCount; i++ ) {
                buffIn = new BufferedInputStream( new FileInputStream( DownloadConfig.SAVE_PATH + DownloadConfig.getInstance().dFile.getName() + i + ".bak" ) );
               
                int b = 0;
                while ( (b = buffIn.read()) != -1 ) {
                    buffOut.write(b);
                }
                buffOut.flush();
                // 关闭输入流
                buffIn.close();
            }
           
            // 删除临时文件
            for ( int i = 0; i < DownloadConfig.getInstance().threadCount; i++ ) {
                File f = new File(DownloadConfig.SAVE_PATH + DownloadConfig.getInstance().dFile.getName() + i + ".bak");  
                if ( f.exists() && f.isFile() ) {
                    f.delete();
                }
            }
        } catch ( Exception e ) {
            System.out.println("异常");
        } finally {
            if ( buffIn != null ) {
                try {
                    buffIn.close();
                } catch ( IOException e ) {
                    buffIn = null;
                }
            }
            if ( buffOut != null ) {
                try {
                    buffOut.close();
                } catch ( IOException e ) {
                    buffOut = null;
                }
            }
        }
    }  
}
class DownloadProcess extends Thread {
    // 线程索引
    private int index;
    // 线程下载最小字节数
    private int cnt;
    // 当前线程需要下载的字节数
    private int size;
   
    public DownloadProcess( int index, int cnt, int size ) {
        this.index = index;
        this.cnt = cnt;
        this.size = size;
    }
    // 线程下载
    public void run() {
        BufferedInputStream buffIn = null;
        BufferedOutputStream buffOut = null;
        try {
            buffIn = new BufferedInputStream(
                    new FileInputStream( DownloadConfig.getInstance().dFile ) );
            buffOut = new BufferedOutputStream(
                    new FileOutputStream(
            DownloadConfig.SAVE_PATH + DownloadConfig.getInstance().dFile.getName() + index + ".bak" ) );
            // 跳过相应的字节
            buffIn.skip( index * cnt );
            int b = 0;
            int num = 0;
            while ( (b = buffIn.read()) != -1 && num < size ) {
                num++;
                buffOut.write(b);
                DownloadConfig.getInstance().threadPercent[index] = num * 1.0 / size;
            }
            // 当前线程下载完毕
            DownloadConfig.getInstance().threadPercent[index] = 1;
            buffOut.flush();
        } catch ( IOException e ) {
            System.out.println("输入输出异常");
        } finally {
            if ( buffIn != null ) {
                try {
                    buffIn.close();
                } catch ( IOException e ) {
                    buffIn = null;
                }
            }
            if ( buffOut != null ) {
                try {
                    buffOut.close();
                } catch ( IOException e ) {
                    buffOut = null;
                }
            }
        }
    }
}
/**
* 文件下载配置类
*/
class DownloadConfig {
   
    // 存储文件的路径
    public static final String SAVE_PATH = "D:\\download";
    // 下载文件
    public File dFile = null;
    // 下载的线程数量
    public int threadCount = 0;
    // 下载线程的进度数组
    public double[] threadPercent = null;
   
    /****** 单例 *******/
    private static DownloadConfig config = new DownloadConfig();
    private DownloadConfig() {}
    public static DownloadConfig getInstance() {
        return config;
    }
}