初学java,java读写文件?

Question

请问java如何读写二进制文件?
如:一个文件8个字节,
前四个字节为(long)销售额,
后面四个字节(long)为入库金额,
C只要几个read和write就能搞定,
java该怎么做啊?
如果我要读前四他字节并显示代码该怎么写?

Answer 1

可以用DataInputStream和DataOutputStream这两个类来写二进制文件

Answer 2

File f=new File(sfileName);
    try{
        FileInputStream fs = new FileInputStream(f);
        DataInputStream rd=new DataInputStream(fs); 
        try{
          x=rd.readLong(); 
        }
        catch(IOException e){
          pmsg("Read total file error: "+e.getMessage(),true);
        }
结果不对，我只要前四个字节的内容

Answer 3

UP... int read(byte[] b)

Answer 4

我的代码有什么问题吗?
    File f=new File(sfileName);
    //byte[] xs=new byte[4];
    try{
        FileInputStream fs = new FileInputStream(f);
        //BufferedInputStream rf= new BufferedInputStream(fs);
        DataInputStream rd=new DataInputStream(fs); 
        try{
          x=rd.readInt();
          t=rd.readInt();
          r=rd.readInt();
          q=rd.readInt();
        }
        catch(IOException e){
          pmsg("Read total file error: "+e.getMessage(),true);
        }
        pmsg("销售额: "+x,true);
        pmsg("退票额: "+t,true);
        pmsg("入库金额: "+r,true);
        pmsg("其他金额: "+q,true);
        try{
          rd.close();
          fs.close();
        }
        catch(IOException e){
          pmsg("close total file error:"+e.getMessage(),true);
        }

Answer 5

import java.io.*;
import java.util.*;
import java.util.zip.*;/**
 *
 * <p>Title: zip文件工具类，压缩和解压缩</p>
 * <p>Description:使用类的组合而非继承关系
 *                不做异常处理
 * </p>
 * <p>Copyright: Copyright (c) 2004</p>
 */
public class ZipTool
{    public static void extractFile(InputStream in, String path,
                                   boolean overWrite) throws IOException
    {        ZipInputStream zisTemp = null;        try
        {
            zisTemp = new ZipInputStream(new BufferedInputStream(in));
            ZipEntry e;            UnZIP zip = new UnZIP(zisTemp, path, overWrite);
            while ( (e = zisTemp.getNextEntry()) != null)
            {
                zip.extractFile(e);
            }
        }
        catch (IOException ex)
        {            ex.printStackTrace();
            throw ex;
        }
        finally
        {
            zisTemp.close();
        }    }    public static void extractFile(InputStream in, String path) throws
        IOException
    {        extractFile(in, path, true);    }    public static void extractFile(String zipFile, String path,
                                   boolean overwrite) throws
        IOException
    {
            if (overwrite)
            {
                extractFile(zipFile, path);
            }
            else
            {
               InputStream in = new FileInputStream(zipFile);
                extractFile(in, path, false);
                in.close();
            }
        }
    public static void extractFile(String zipFile, String path) throws
        IOException
    {        FileInputStream fin = null;
        try
        {
            fin = new FileInputStream(zipFile);
            extractFile(fin, path);
        }
        catch (IOException ex)
        {            ex.printStackTrace();
            throw ex;
        }        finally
        {
            if (fin != null)
            {
                fin.close();
            }
        }    }    /**
     * 把多文件或目录压缩成一个ZIP文件
     * @param ZIPfileName  目标zip文件名(全路径)
     * @param fileNames 源文件或目录名列表
     * @throws IOException
     */    /* For example
     ArrayList fileList = new ArrayList();
        fileList.add("c:\\hh\\tt.txt");
        fileList.add("c:\\hh\\tt1.txt");
        fileList.add("c:\\hh\\tt2.txt");
        //目录
        fileList.add("c:\\hh\\yy");
        ZipTool.ZipFile("c:\\temp.zip", fileList);
        ZipTool.extractFile("c:\\temp.zip", "c:\\hh1");
     */
    public static void ZipFile(String ZIPfileName, List fileNames) throws
        IOException
    {        if (fileNames == null || fileNames.size() == 0)
        {            throw new IllegalArgumentException("param fileNames is null!");        }        File[] files = new File[fileNames.size()];
        for (int i = 0; i < fileNames.size(); i++)
        {
            files[i] = new File( (String) fileNames.get(i));
        }
        ZipFile(ZIPfileName, files);    }    public static void ZipFile(String ZIPfileName, File[] files) throws
        IOException
    {        if (files == null || files.length == 0)
        {            throw new IllegalArgumentException("param fileNames is null!");        }
        ZipOutputStream zout = null;        try
        {
            zout = new ZipOutputStream(new FileOutputStream(new File(
                ZIPfileName)));            for (int i = 0; i < files.length; i++)
            {
                String filePath = (String) files[i].getAbsolutePath();
                String rootPath = getParentPath(filePath);
                ZIP ziptool = new ZIP(zout, rootPath);
                ziptool.ZipFile(filePath);
            }
        }
        catch (IOException ex)
        {            ex.printStackTrace();
            throw ex;
        }        finally
        {
            if (null != zout)
            {
                zout.closeEntry();
                zout.close();
            }        }    }    /**
     * 压缩一个文件或文件夹到ZIP文件
     * @param ZIPfileName
     * @param filePath
     * @throws IOException
     */
    public static void ZipFile(String ZIPfileName, String filePath) throws
        IOException
    {        FileOutputStream fout = null;
        try
        {
            fout = new FileOutputStream(ZIPfileName);
            ZipFile(fout, filePath);
        }
        catch (IOException ex)
        {
            ex.printStackTrace();
            throw ex;
        }
        finally
        {
            if (fout != null)
            {
                fout.close();
            }
        }
    }    /**
     * 压缩一个文件或文件夹到一个字节数组
     * @param filePath
     * @return
     * @throws IOException
     */
    public static void ZipFile(OutputStream out, String filePath) throws
        IOException
    {        ZipOutputStream zout = null;
        try
        {            zout = new ZipOutputStream(new BufferedOutputStream(out));
            String rootPath = getParentPath(filePath);            new ZIP(zout, rootPath).ZipFile(filePath);        }
        catch (IOException ex)
        {
            ex.printStackTrace();
            throw ex;
        }        finally
        {
            if (null != zout)
            {
                zout.closeEntry();
                zout.close();
            }        }    }

Answer 6

    /**
     * 返回文件上级的目录名称
     * @param absoluteFile
     * @return
     */
    private static String getParentPath(String fileName)
    {        File tempFile = new File(fileName);
        File parentFile = new File(tempFile.getAbsolutePath()).getParentFile();
        return parentFile.getAbsolutePath();
    }}class ZIP
{    ZIP(ZipOutputStream zout, String rootPath)
    {        this.zout = zout;
        this.rootPath = rootPath;    }    private ZipOutputStream zout = null;
    private String rootPath = "/";    /**
     * 递规实现压缩文件
     * @param filePath
     * @throws IOException
     */
    protected void ZipFile(String filePath) throws IOException
    {
       if(filePath.indexOf("\\")!=-1)
    {
         filePath=filePath.replaceAll("\\\\","\\/");
      }        File f = new File(filePath);        String absolutePath = f.getAbsolutePath();
        f = new File(absolutePath);
        String entryName = absolutePath.substring(absolutePath.indexOf(rootPath) +
                                                  rootPath.length());
        if (f.isDirectory())
        {            ZipEntry ze = new ZipEntry(entryName + "/");
            zout.putNextEntry(ze);            File[] fileList = f.listFiles();
            for (int i = 0; i < fileList.length; i++)
            {
                File subP = fileList[i];
                ZipFile(subP.getAbsolutePath());
            }
        }
        else
        {
            if(entryName.indexOf("\\")!=-1)
            {
                entryName=entryName.replaceAll("\\\\","\\/");
            }            writeEntry(entryName, f);
        }    }    /**
     * 写文件到ZIP
     * @param entryName
     * @param in
     * @throws IOException
     */
    protected void writeEntry(String entryName, File f) throws IOException
    {        ZipEntry ze = new ZipEntry(entryName);
        zout.putNextEntry(ze);
        DataInputStream din = new DataInputStream(new BufferedInputStream(new
            FileInputStream(f)));        //经典中的经典
        byte[] b= new byte[1024];
        int len = 0;
        while ( (len = din.read(b)) != -1)
        {
            zout.write(b, 0, len);
        }
        din.close();    }}class UnZIP
{    UnZIP(ZipInputStream zin, String rootPath, boolean overwrite)
    {       this.zin = zin;
        this.rootPath = rootPath;
        this.overwrite = overwrite;    }    private ZipInputStream zin = null;
    private String rootPath = "/";
    private boolean overwrite = true;    /**
     *
     * @param e
     * @throws IOException
     */
    protected void extractFile(ZipEntry e) throws IOException
    {        String name = e.getName();
        if(name!=null&&name.startsWith("\\")){
          name = name.substring(1,name.length());
        }
        if(name.indexOf("\\")!=-1)
        {
            name=name.replaceAll("\\\\","\\/");        }        File f = new File(rootPath +"/"+ name);        if (e.isDirectory())
        {
            if (!f.exists() && !f.mkdirs() || !f.isDirectory())
            {
                throw new IOException(new StringBuffer().append("创建目录").append(
                    e.getName()).append("失败").toString());
            }
        }
        else
        {            //如果文件存在，而且不允许覆盖返回不处理
            if (f.exists() && !overwrite)
            {                return;
            }
            if (f.getParent() != null)
            {
                File d = new File(f.getParent());
                if (!d.exists() && !d.mkdirs() || !d.isDirectory())
                {
                    throw new IOException(new StringBuffer().append("创建文件").
                                          append(f.getName()).append("的父目录时失败").
                                          toString());
                }
            }
            OutputStream os = new FileOutputStream(f);
            byte[] b = new byte[1024];
            int len;
            while ( (len = zin.read(b)) != -1)
            {
                os.write(b, 0, len);
            }
            zin.closeEntry();
            os.close();
        }
    }
    /**
     * 删除文件
     * @param absoluteName
     * @return
     * @throws IOException
     */
    public String deleteTree(String absoluteName) throws IOException
    {
        String flag = "failure";
        File dir = new File(absoluteName);        //如果不存在
        if (!dir.exists())
        {
            flag = "noexist";
        }
        //如果不是目录
        else if (!dir.isDirectory())
        {            if (dir.delete())
            {
                flag = "success";
            }        }
        else
        {            //是目录
            File[] entries = dir.listFiles();
            int sz = entries.length;
            for (int i = 0; i < sz; i++)
            {
                if (entries[i].isDirectory())
                {
                    deleteTree(entries[i].getAbsolutePath());
                }
                else
                {
                    entries[i].delete();
                }
            }
            if (dir.delete())
            {
                flag = "success";
            }
        }
        return flag;
    }}

Answer 7

/**
     * 一对多文件传输
     * @param temZip
     * @param pathName
     * @throws RemoteException
     * @throws IOException
     */
    public ArrayList transferFile_M(ArrayList to, ArrayList files, String path) throws
        IOException, CustomAccessException
    {
        AuthorizationHelper.checkValidity();        //传输结果
        ArrayList result = new ArrayList();        long now = System.currentTimeMillis();
        //临时文件
        String localZip = TEMP_PATH + now + "local.tmp";
        String remoteZip = TEMP_PATH + now + "remote.tmp";
        DataInputStream din = null;        try
        {
            //压缩文件到临时文件
            zip(localZip, files);            //要传的机器数
            int j = to.size();
            for (int i = 0; i < j; i++)
            {
                try
                {
                    boolean overwrite;
                    String ss = (String) to.get(i);
                    if (ss.endsWith("y"))
                    {
                        overwrite = true;
                    }
                    else
                    {
                        overwrite = false;
                    }
                    String css = ss.substring(0, ss.length() - 1);
                    //绑定远程对象
                    FileTransfer fter = (FileTransfer) Naming.lookup("rmi://" +
                        css + "/" + REBIND_NAME);
                    if(!fter.isHaveDriver(path))
                    {
                        throw new Exception("not contain");
                    }
                    din = new DataInputStream(new
                                              BufferedInputStream(new
                        FileInputStream(localZip)));
                    fter.startMonitor(remoteZip);
                    int len = 0;
                    byte[] b = new byte[1024 * 1024];
                    //在本地读，往远程写                    while ( (len = (din.read(b))) >= 0)
                    {                        fter.write(remoteZip, b, len);                    }
                    din.close();
                    //远程文件解压
                    fter.unZip(remoteZip, path, overwrite);
                    //删除远程文件
                    fter.remove(remoteZip);
                    //记录操作结果
                    result.add(new ResultObject(css, "s",""));                }
                catch (Exception ex)
                {
                    ROLog.getLog().error("Exception", ex);
                    //记录操作结果
                    String sto = (String) to.get(i);
                    sto = sto.substring(0, sto.length() - 1);
                    if("not contain".equals(ex.getMessage()))
                    {
                         result.add(new ResultObject(sto, "f","filetransfer.erromessage3"));
                    }
                    else if("Unzip".equals(ex.getMessage()))
                      {
                        result.add(new  ResultObject(sto, "f","filetransfer.erromessage4"));
                       }
                     else
                    {
                       result.add(new ResultObject(sto, "f","filetransfer.erromessage1"));
                    }                }            }        }        finally
        {
            //删除本地临时文件
            if (din != null)
            {
                din.close();
            }
            remove(localZip);        }        return result;
    }