Commons IO example source code file (FileEntry.java)

This example Commons IO source code file (FileEntry.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Commons IO tags/keywords

empty_entries, empty_entries, file, file, fileentry, fileentry, illegalargumentexception, io, serializable, string, string

The Commons IO FileEntry.java source code

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF 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 org.apache.commons.io.monitor;

import java.io.File;
import java.io.Serializable;

/**
 * {@link FileEntry} represents the state of a file or directory, capturing
 * the following {@link File} attributes at a point in time.
 * <ul>
 *   <li>File Name (see {@link File#getName()})
 *   <li>Exists - whether the file exists or not (see {@link File#exists()})
 *   <li>Directory - whether the file is a directory or not (see {@link File#isDirectory()})
 *   <li>Last Modified Date/Time (see {@link File#lastModified()})
 *   <li>Length (see {@link File#length()}) - directories treated as zero
 *   <li>Children - contents of a directory (see {@link File#listFiles(java.io.FileFilter)})
 * </ul>
 * <p>
 * <h3>Custom Implementations
 * If the state of additional {@link File} attributes is required then create a custom
 * {@link FileEntry} with properties for those attributes. Override the
 * {@link #newChildInstance(File)} to return a new instance of the appropriate type.
 * You may also want to override the {@link #refresh(File)} method.
 * @see FileAlterationObserver
 * @since Commons IO 2.0
 */
public class FileEntry implements Serializable {

    static final FileEntry[] EMPTY_ENTRIES = new FileEntry[0];

    private final FileEntry parent;
    private FileEntry[] children;
    private final File file;
    private String name;
    private boolean exists;
    private boolean directory;
    private long lastModified;
    private long length;

    /**
     * Construct a new monitor for a specified {@link File}.
     *
     * @param file The file being monitored
     */
    public FileEntry(File file) {
        this((FileEntry)null, file);
    }

    /**
     * Construct a new monitor for a specified {@link File}.
     *
     * @param parent The parent
     * @param file The file being monitored
     */
    public FileEntry(FileEntry parent, File file) {
        if (file == null) {
            throw new IllegalArgumentException("File is missing");
        }
        this.file = file;
        this.parent = parent;
        this.name = file.getName();
    }

    /**
     * Refresh the attributes from the {@link File}, indicating
     * whether the file has changed.
     * <p>
     * This implementation refreshes the <code>name, exists,
     * <code>directory, lastModified and length
     * properties.
     * <p>
     * The <code>exists, directory, lastModified
     * and <code>length properties are compared for changes
     *
     * @param file the file instance to compare to
     * @return <code>true if the file has changed, otherwise false
     */
    public boolean refresh(File file) {

        // cache original values
        boolean origExists       = exists;
        long    origLastModified = lastModified;
        boolean origDirectory    = directory;
        long    origLength       = length;

        // refresh the values
        name         = file.getName();
        exists       = file.exists();
        directory    = (exists ? file.isDirectory() : false);
        lastModified = (exists ? file.lastModified() : 0);
        length       = (exists && !directory ? file.length() : 0);

        // Return if there are changes
        return (exists != origExists ||
                lastModified != origLastModified ||
                directory != origDirectory ||
                length != origLength);
    }

    /**
     * Create a new child instance.
     * <p>
     * Custom implementations should override this method to return
     * a new instance of the appropriate type.
     *
     * @param file The child file
     * @return a new child instance
     */
    public FileEntry newChildInstance(File file) {
        return new FileEntry(this, file);
    }

    /**
     * Return the parent entry.
     *
     * @return the parent entry
     */
    public FileEntry getParent() {
        return parent;
    }

    /**
     * Return the level
     *
     * @return the level
     */
    public int getLevel() {
        return parent == null ? 0 : parent.getLevel() + 1;
    }

    /**
     * Return the directory's files.
     *
     * @return This directory's files or an empty
     * array if the file is not a directory or the
     * directory is empty
     */
    public FileEntry[] getChildren() {
        return children != null ? children : EMPTY_ENTRIES;
    }

    /**
     * Set the directory's files.
     *
     * @param children This directory's files, may be null
     */
    public void setChildren(FileEntry[] children) {
        this.children = children;
    }

    /**
     * Return the file being monitored.
     *
     * @return the file being monitored
     */
    public File getFile() {
        return file;
    }

    /**
     * Return the file name.
     *
     * @return the file name
     */
    public String getName() {
        return name;
    }

    /**
     * Set the file name.
     *
     * @param name the file name
     */
    public void setName(String name) {
        this.name = name;
    }

    /**
     * Return the last modified time from the last time it
     * was checked.
     *
     * @return the last modified time
     */
    public long getLastModified() {
        return lastModified;
    }

    /**
     * Return the last modified time from the last time it
     * was checked.
     *
     * @param lastModified The last modified time
     */
    public void setLastModified(long lastModified) {
        this.lastModified = lastModified;
    }

    /**
     * Return the length.
     *
     * @return the length
     */
    public long getLength() {
        return length;
    }

    /**
     * Set the length.
     *
     * @param length the length
     */
    public void setLength(long length) {
        this.length = length;
    }

    /**
     * Indicate whether the file existed the last time it
     * was checked.
     *
     * @return whether the file existed
     */
    public boolean isExists() {
        return exists;
    }

    /**
     * Set whether the file existed the last time it
     * was checked.
     *
     * @param exists whether the file exists or not
     */
    public void setExists(boolean exists) {
        this.exists = exists;
    }

    /**
     * Indicate whether the file is a directory or not.
     *
     * @return whether the file is a directory or not
     */
    public boolean isDirectory() {
        return directory;
    }

    /**
     * Set whether the file is a directory or not.
     *
     * @param directory whether the file is a directory or not
     */
    public void setDirectory(boolean directory) {
        this.directory = directory;
    }
}