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Thinking in Java
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Checking for and creating directories

The File class is more than just a representation for an existing file or directory. You can also use a File object to create a new directory or an entire directory path if it doesn’t exist. You can also look at the characteristics of files (size, last modification date, read/write), see whether a File object represents a file or a directory, and delete a file. This program shows some of the other methods available with the File class (see the HTML documentation from for the full set):

// Demonstrates the use of the File class to
// create directories and manipulate files.
// {Args: MakeDirectoriesTest}
import com.bruceeckel.simpletest.*;

public class MakeDirectories {
  private static Test monitor = new Test();
  private static void 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");
  private static void fileData(File f) {
      "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());
      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();
        old = new File(args[1]),
        rname = new File(args[2]);
      return; // Exit main
    int count = 0;
    boolean del = false;
    if(args[0].equals("-d")) {
      del = true;
    while(++count < args.length) {
      File f = new File(args[count]);
      if(f.exists()) {
        System.out.println(f + " exists");
        if(del) {
          System.out.println("deleting..." + f);
      else { // Doesn't exist
        if(!del) {
          System.out.println("created " + f);
    if(args.length == 1 &&
      monitor.expect(new String[] {
        "%% (MakeDirectoriesTest exists"+
          "|created MakeDirectoriesTest)",
        "%% Absolute path: "
          + "\\S+MakeDirectoriesTest",
        "%%  Can read: (true|false)",
        "%%  Can write: (true|false)",
        " getName: MakeDirectoriesTest",
        " getParent: null",
        " getPath: MakeDirectoriesTest",
        "%%  length: \\d+",
        "%%  lastModified: \\d+",
        "It's a directory"
} ///:~

In fileData( ) you can see various file investigation methods used to display information about the file or directory path.

The first method that’s exercised by main( ) is renameTo( ), which allows you to rename (or move) a file to an entirely new path represented by the argument, which is another File object. This also works with directories of any length.

If you experiment with the preceding program, you’ll find that you can make a directory path of any complexity, because mkdirs( ) will do all the work for you.
Thinking in Java
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   Reproduced courtesy of Bruce Eckel, MindView, Inc. Design by Interspire