Java IO系统

目录列表器

import java.io.*;

public class DirList {
  public static void main(String[] args) {
    try {
      File path = new File(".");
      String[] list;
      if(args.length == 0)
        list = path.list();
      else 
        list = path.list(new DirFilter(args[0]));
      for(int i = 0; i < list.length; i++)
        System.out.println(list[i]);
    } catch(Exception e) {
      e.printStackTrace();
    }
  }
}

class DirFilter implements FilenameFilter {
  String afn;
  DirFilter(String afn) { this.afn = afn; }
  public boolean accept(File dir, String name) {
    // Strip path information:
    String f = new File(name).getName();
    return f.indexOf(afn) != -1;
  }
} ///:~


import java.io.*;

public class DirList2 {
  public static FilenameFilter 
  filter(final String afn) {
    // Creation of anonymous inner class:
    return new FilenameFilter() {
      String fn = afn;
      public boolean accept(File dir, String n) {
        // Strip path information:
        String f = new File(n).getName();
        return f.indexOf(fn) != -1;
      }
    }; // End of anonymous inner class
  }
  public static void main(String[] args) {
    try {
      File path = new File(".");
      String[] list;
      if(args.length == 0)
        list = path.list();
      else 
        list = path.list(filter(args[0]));
      for(int i = 0; i < list.length; i++)
        System.out.println(list[i]);
    } catch(Exception e) {
      e.printStackTrace();
    }
  }
} ///:~

import java.io.*;

public class MakeDirectories {
  private final static String usage =
    "Usage:MakeDirectories path1 ...\n" +
    "Creates each path\n" +
    "Usage:MakeDirectories -d path1 ...\n" +
    "Deletes each path\n" +
    "Usage:MakeDirectories -r path1 path2\n" +
    "Renames from path1 to path2\n";
  private static void usage() {
    System.err.println(usage);
    System.exit(1);
  }
  private static void fileData(File f) {
    System.out.println(
      "Absolute path: " + f.getAbsolutePath() +
      "\n Can read: " + f.canRead() +
      "\n Can write: " + f.canWrite() +
      "\n getName: " + f.getName() +
      "\n getParent: " + f.getParent() +
      "\n getPath: " + f.getPath() +
      "\n length: " + f.length() +
      "\n lastModified: " + f.lastModified());
    if(f.isFile())
      System.out.println("it's a file");
    else if(f.isDirectory())
      System.out.println("it's a directory");
  }
  public static void main(String[] args) {
    if(args.length < 1) usage();
    if(args[0].equals("-r")) {
      if(args.length != 3) usage();
      File 
        old = new File(args[1]),
        rname = new File(args[2]);
      old.renameTo(rname);
      fileData(old);
      fileData(rname);
      return; // Exit main
    }
    int count = 0;
    boolean del = false;
    if(args[0].equals("-d")) {
      count++;
      del = true;
    }
    for( ; count < args.length; count++) {
      File f = new File(args[count]);
      if(f.exists()) {
        System.out.println(f + " exists");
        if(del) {
          System.out.println("deleting..." + f);
          f.delete();
        }
      } 
      else { // Doesn't exist
        if(!del) {
          f.mkdirs();
          System.out.println("created " + f);
        }
      }
      fileData(f);
    }  
  }
} ///:~

import java.io.*;
import com.bruceeckel.tools.*;

public class IOStreamDemo {
  public static void main(String[] args) {
    try {
      // 1. Buffered input file
      DataInputStream in =
        new DataInputStream(
          new BufferedInputStream(
            new FileInputStream(args[0])));
      String s, s2 = new String();
      while((s = in.readLine())!= null)
        s2 += s + "\n";
      in.close();

      // 2. Input from memory
      StringBufferInputStream in2 =
          new StringBufferInputStream(s2);
      int c;
      while((c = in2.read()) != -1)
        System.out.print((char)c);

      // 3. Formatted memory input
      try {
        DataInputStream in3 =
          new DataInputStream(
            new StringBufferInputStream(s2));
        while(true)
          System.out.print((char)in3.readByte());
      } catch(EOFException e) {
        System.out.println(
          "End of stream encountered");
      }

      // 4. Line numbering & file output
      try {
        LineNumberInputStream li =
          new LineNumberInputStream(
            new StringBufferInputStream(s2));
        DataInputStream in4 =
          new DataInputStream(li);
        PrintStream out1 =
          new PrintStream(
            new BufferedOutputStream(
              new FileOutputStream(
                "IODemo.out")));
        while((s = in4.readLine()) != null )
          out1.println(
            "Line " + li.getLineNumber() + s);
        out1.close(); // finalize() not reliable!
      } catch(EOFException e) {
        System.out.println(
          "End of stream encountered");
      }

      // 5. Storing & recovering data
      try {
        DataOutputStream out2 =
          new DataOutputStream(
            new BufferedOutputStream(
              new FileOutputStream("Data.txt")));
        out2.writeBytes(
          "Here's the value of pi: \n");
        out2.writeDouble(3.14159);
        out2.close();
        DataInputStream in5 =
          new DataInputStream(
            new BufferedInputStream(
              new FileInputStream("Data.txt")));
        System.out.println(in5.readLine());
        System.out.println(in5.readDouble());
      } catch(EOFException e) {
        System.out.println(
          "End of stream encountered");
      }

      // 6. Reading/writing random access files
      RandomAccessFile rf =
        new RandomAccessFile("rtest.dat", "rw");
      for(int i = 0; i < 10; i++)
        rf.writeDouble(i*1.414);
      rf.close();

      rf =
        new RandomAccessFile("rtest.dat", "rw");
      rf.seek(5*8);
      rf.writeDouble(47.0001);
      rf.close();

      rf =
        new RandomAccessFile("rtest.dat", "r");
      for(int i = 0; i < 10; i++)
        System.out.println(
          "Value " + i + ": " +
          rf.readDouble());
      rf.close();

      // 7. File input shorthand
      InFile in6 = new InFile(args[0]);
      String s3 = new String();
      System.out.println(
        "First line in file: " +
        in6.readLine());
        in6.close();

      // 8. Formatted file output shorthand
      PrintFile out3 = new PrintFile("Data2.txt");
      out3.print("Test of PrintFile");
      out3.close();

      // 9. Data file output shorthand
      OutFile out4 = new OutFile("Data3.txt");
      out4.writeBytes("Test of outDataFile\n\r");
      out4.writeChars("Test of outDataFile\n\r");
      out4.close();

    } catch(FileNotFoundException e) {
      System.out.println(
        "File Not Found:" + args[0]);
    } catch(IOException e) {
      System.out.println("IO Exception");
    }
  }