delete.java

java 的164个例子的源代码,包括了 很多方面,供包括了19个方面的 源代码

/*
 * Copyright (c) 2000 David Flanagan.  All rights reserved.
 * This code is from the book Java Examples in a Nutshell, 2nd Edition.
 * It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or implied.
 * You may study, use, and modify it for any non-commercial purpose.
 * You may distribute it non-commercially as long as you retain this notice.
 * For a commercial use license, or to purchase the book (recommended),
 * visit http://www.davidflanagan.com/javaexamples2.
 */
package com.davidflanagan.examples.io;
import java.io.*;

/**
 * This class is a static method delete() and a standalone program that
 * deletes a specified file or directory.
 **/
public class Delete {
    /** 
     * This is the main() method of the standalone program.  After checking
     * it arguments, it invokes the Delete.delete() method to do the deletion
     **/
    public static void main(String[] args) {
        if (args.length != 1) {    // Check command-line arguments
            System.err.println("Usage: java Delete <file or directory>");
            System.exit(0);
        }
        // Call delete() and display any error messages it throws.
        try { delete(args[0]); }
        catch (IllegalArgumentException e) {
	    System.err.println(e.getMessage());
	}
    }     
    
    /**
     * The static method that does the deletion.  Invoked by main(), and
     * designed for use by other programs as well.  It first makes sure that
     * the specified file or directory is deleteable before attempting to
     * delete it.  If there is a problem, it throws an
     * IllegalArgumentException.
     **/
    public static void delete(String filename) {
        // Create a File object to represent the filename
        File f = new File(filename);

        // Make sure the file or directory exists and isn't write protected
        if (!f.exists()) fail("Delete: no such file or directory: " +filename);
        if (!f.canWrite()) fail("Delete: write protected: " + filename);

        // If it is a directory, make sure it is empty
        if (f.isDirectory()) {
            String[] files = f.list();
            if (files.length > 0)
		fail("Delete: directory not empty: " + filename);
        }

        // If we passed all the tests, then attempt to delete it
        boolean success = f.delete();
	
        // And throw an exception if it didn't work for some (unknown) reason.
        // For example, because of a bug with Java 1.1.1 on Linux, 
        // directory deletion always fails 
        if (!success) fail("Delete: deletion failed");
    }

    /** A convenience method to throw an exception */
    protected static void fail(String msg) throws IllegalArgumentException {
        throw new IllegalArgumentException(msg);
    }
}