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 * 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
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 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
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 * See the License for the specific language governing permissions and
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package org.apache.commons.io;

import java.io.File;
import java.io.IOException;

Strategy for deleting files.

There is more than one way to delete a file.
You may want to limit access to certain directories, to only delete
directories if they are empty, or maybe to force deletion.

This class captures the strategy to use and is designed for user subclassing.
Since:
1.3/**
 * Strategy for deleting files.
 * <p>
 * There is more than one way to delete a file.
 * You may want to limit access to certain directories, to only delete
 * directories if they are empty, or maybe to force deletion.
 * <p>
 * This class captures the strategy to use and is designed for user subclassing.
 *
 * @since 1.3
 */
public class FileDeleteStrategy {

    
The singleton instance for normal file deletion, which does not permit
the deletion of directories that are not empty.
/**
     * The singleton instance for normal file deletion, which does not permit
     * the deletion of directories that are not empty.
     */
    public static final FileDeleteStrategy NORMAL = new FileDeleteStrategy("Normal");
    
The singleton instance for forced file deletion, which always deletes,
even if the file represents a non-empty directory.
/**
     * The singleton instance for forced file deletion, which always deletes,
     * even if the file represents a non-empty directory.
     */
    public static final FileDeleteStrategy FORCE = new ForceFileDeleteStrategy();

    
The name of the strategy. /** The name of the strategy. */
    private final String name;

    //-----------------------------------------------------------------------
    
Restricted constructor.
Params:
name –  the name by which the strategy is known/**
     * Restricted constructor.
     *
     * @param name  the name by which the strategy is known
     */
    protected FileDeleteStrategy(final String name) {
        this.name = name;
    }

    //-----------------------------------------------------------------------
    
Deletes the file object, which may be a file or a directory.
All IOExceptions are caught and false returned instead.
If the file does not exist or is null, true is returned.
 Subclass writers should override doDelete(File), not this method. 
Params:
fileToDelete –  the file to delete, null returns true
Returns:
true if the file was deleted, or there was no such file/**
     * Deletes the file object, which may be a file or a directory.
     * All <code>IOException</code>s are caught and false returned instead.
     * If the file does not exist or is null, true is returned.
     * <p>
     * Subclass writers should override {@link #doDelete(File)}, not this method.
     *
     * @param fileToDelete  the file to delete, null returns true
     * @return true if the file was deleted, or there was no such file
     */
    public boolean deleteQuietly(final File fileToDelete) {
        if (fileToDelete == null || fileToDelete.exists() == false) {
            return true;
        }
        try {
            return doDelete(fileToDelete);
        } catch (final IOException ex) {
            return false;
        }
    }

    
Deletes the file object, which may be a file or a directory.
If the file does not exist, the method just returns.
 Subclass writers should override doDelete(File), not this method. 
Params:
fileToDelete –  the file to delete, not null
Throws:
NullPointerException – if the file is null
IOException – if an error occurs during file deletion/**
     * Deletes the file object, which may be a file or a directory.
     * If the file does not exist, the method just returns.
     * <p>
     * Subclass writers should override {@link #doDelete(File)}, not this method.
     *
     * @param fileToDelete  the file to delete, not null
     * @throws NullPointerException if the file is null
     * @throws IOException if an error occurs during file deletion
     */
    public void delete(final File fileToDelete) throws IOException {
        if (fileToDelete.exists() && doDelete(fileToDelete) == false) {
            throw new IOException("Deletion failed: " + fileToDelete);
        }
    }

    
Actually deletes the file object, which may be a file or a directory.

This method is designed for subclasses to override.
The implementation may return either false or an IOException when deletion fails. The delete(File) and deleteQuietly(File) methods will handle either response appropriately. A check has been made to ensure that the file will exist. 
 This implementation uses File.delete(). 
Params:
fileToDelete –  the file to delete, exists, not null
Throws:
NullPointerException – if the file is null
IOException – if an error occurs during file deletion
Returns:
true if the file was deleted/**
     * Actually deletes the file object, which may be a file or a directory.
     * <p>
     * This method is designed for subclasses to override.
     * The implementation may return either false or an <code>IOException</code>
     * when deletion fails. The {@link #delete(File)} and {@link #deleteQuietly(File)}
     * methods will handle either response appropriately.
     * A check has been made to ensure that the file will exist.
     * <p>
     * This implementation uses {@link File#delete()}.
     *
     * @param fileToDelete  the file to delete, exists, not null
     * @return true if the file was deleted
     * @throws NullPointerException if the file is null
     * @throws IOException if an error occurs during file deletion
     */
    protected boolean doDelete(final File fileToDelete) throws IOException {
        return fileToDelete.delete();
    }

    //-----------------------------------------------------------------------
    
Gets a string describing the delete strategy.
Returns:
a string describing the delete strategy/**
     * Gets a string describing the delete strategy.
     *
     * @return a string describing the delete strategy
     */
    @Override
    public String toString() {
        return "FileDeleteStrategy[" + name + "]";
    }

    //-----------------------------------------------------------------------
    
Force file deletion strategy.
/**
     * Force file deletion strategy.
     */
    static class ForceFileDeleteStrategy extends FileDeleteStrategy {
        
Default Constructor /** Default Constructor */
        ForceFileDeleteStrategy() {
            super("Force");
        }

        
Deletes the file object.

This implementation uses FileUtils.forceDelete()
if the file exists.
Params:
fileToDelete –  the file to delete, not null
Throws:
NullPointerException – if the file is null
IOException – if an error occurs during file deletion
Returns:
Always returns true/**
         * Deletes the file object.
         * <p>
         * This implementation uses <code>FileUtils.forceDelete()</code>
         * if the file exists.
         *
         * @param fileToDelete  the file to delete, not null
         * @return Always returns {@code true}
         * @throws NullPointerException if the file is null
         * @throws IOException if an error occurs during file deletion
         */
        @Override
        protected boolean doDelete(final File fileToDelete) throws IOException {
            FileUtils.forceDelete(fileToDelete);
            return true;
        }
    }

}