Implements the same behaviour as the "touch" utility on Unix. - Java Native OS

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Description

Implements the same behaviour as the "touch" utility on Unix.

Demo Code

/**//from w w  w. j  av a 2 s .c  om
 * Licensed to Jasig under one or more contributor license
 * agreements. See the NOTICE file distributed with this work
 * for additional information regarding copyright ownership.
 * Jasig licenses this file to you under the Apache License,
 * Version 2.0 (the "License"); you may not use this file
 * except in compliance with the License. You may obtain a
 * copy of the License at:
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on
 * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied. See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
//package com.java2s;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

public class Main {
    public static void main(String[] argv) throws Exception {
        File file = new File("Main.java");
        touch(file);
    }

    /**
     * Implements the same behaviour as the "touch" utility on Unix. It creates
     * a new file with size 0 or, if the file exists already, it is opened and
     * closed without modifying it, but updating the file date and time.
     * <p>
     * NOTE: As from v1.3, this method throws an IOException if the last
     * modified date of the file cannot be set. Also, as from v1.3 this method
     * creates parent directories if they do not exist.
     *
     * @param file  the File to touch
     * @throws IOException If an I/O problem occurs
     */
    static void touch(File file) throws IOException {
        if (!file.exists()) {
            OutputStream out = openOutputStream(file);
            closeQuietly(out);
        }
        boolean success = file.setLastModified(System.currentTimeMillis());
        if (!success) {
            throw new IOException(
                    "Unable to set the last modification time for " + file);
        }
    }

    /**
     * Opens a {@link FileOutputStream} for the specified file, checking and
     * creating the parent directory if it does not exist.
     * <p>
     * At the end of the method either the stream will be successfully opened,
     * or an exception will have been thrown.
     * <p>
     * The parent directory will be created if it does not exist.
     * The file will be created if it does not exist.
     * An exception is thrown if the file object exists but is a directory.
     * An exception is thrown if the file exists but cannot be written to.
     * An exception is thrown if the parent directory cannot be created.
     * 
     * @param file  the file to open for output, must not be <code>null</code>
     * @return a new {@link FileOutputStream} for the specified file
     * @throws IOException if the file object is a directory
     * @throws IOException if the file cannot be written to
     * @throws IOException if a parent directory needs creating but that fails
     * @since Commons IO 1.3
     */
    static FileOutputStream openOutputStream(File file) throws IOException {
        if (file.exists()) {
            if (file.isDirectory()) {
                throw new IOException("File '" + file
                        + "' exists but is a directory");
            }
            if (file.canWrite() == false) {
                throw new IOException("File '" + file
                        + "' cannot be written to");
            }
        } else {
            File parent = file.getParentFile();
            if (parent != null && parent.exists() == false) {
                if (parent.mkdirs() == false) {
                    throw new IOException("File '" + file
                            + "' could not be created");
                }
            }
        }
        return new FileOutputStream(file);
    }

    /**
     * Unconditionally close an <code>OutputStream</code>.
     * <p>
     * Equivalent to {@link OutputStream#close()}, except any exceptions will be ignored.
     * This is typically used in finally blocks.
     *
     * @param output  the OutputStream to close, may be null or already closed
     */
    static void closeQuietly(OutputStream output) {
        try {
            if (output != null) {
                output.close();
            }
        } catch (IOException ioe) {
            // ignore
        }
    }

    /**
     * Unconditionally close an <code>InputStream</code>.
     * <p>
     * Equivalent to {@link InputStream#close()}, except any exceptions will be ignored.
     * This is typically used in finally blocks.
     *
     * @param input  the InputStream to close, may be null or already closed
     */
    static void closeQuietly(InputStream input) {
        try {
            if (input != null) {
                input.close();
            }
        } catch (IOException ioe) {
            // ignore
        }
    }
}

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