Commons IO example source code file (PrefixFileFilter.java)

This example Commons IO source code file (PrefixFileFilter.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

abstractfilefilter, illegalargumentexception, io, iocase, iocase, override, prefixfilefilter, prefixfilefilter, serializable, string, string, stringbuilder, the, the, util

The Commons IO PrefixFileFilter.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.filefilter;

import java.io.File;
import java.io.Serializable;
import java.util.List;

import org.apache.commons.io.IOCase;

/**
 * Filters filenames for a certain prefix.
 * <p>
 * For example, to print all files and directories in the 
 * current directory whose name starts with <code>Test:
 *
 * <pre>
 * File dir = new File(".");
 * String[] files = dir.list( new PrefixFileFilter("Test") );
 * for ( int i = 0; i < files.length; i++ ) {
 *     System.out.println(files[i]);
 * }
 * </pre>
 *
 * @since Commons IO 1.0
 * @version $Revision: 1005099 $ $Date: 2010-10-06 17:13:01 +0100 (Wed, 06 Oct 2010) $
 * 
 * @author Stephen Colebourne
 * @author Federico Barbieri
 * @author Serge Knystautas
 * @author Peter Donald
 * @see FileFilterUtils#prefixFileFilter(String)
 * @see FileFilterUtils#prefixFileFilter(String, IOCase)
 */
public class PrefixFileFilter extends AbstractFileFilter implements Serializable {
    
    /** The filename prefixes to search for */
    private final String[] prefixes;

    /** Whether the comparison is case sensitive. */
    private final IOCase caseSensitivity;

    /**
     * Constructs a new Prefix file filter for a single prefix.
     * 
     * @param prefix  the prefix to allow, must not be null
     * @throws IllegalArgumentException if the prefix is null
     */
    public PrefixFileFilter(String prefix) {
        this(prefix, IOCase.SENSITIVE);
    }

    /**
     * Constructs a new Prefix file filter for a single prefix 
     * specifying case-sensitivity.
     * 
     * @param prefix  the prefix to allow, must not be null
     * @param caseSensitivity  how to handle case sensitivity, null means case-sensitive
     * @throws IllegalArgumentException if the prefix is null
     * @since Commons IO 1.4
     */
    public PrefixFileFilter(String prefix, IOCase caseSensitivity) {
        if (prefix == null) {
            throw new IllegalArgumentException("The prefix must not be null");
        }
        this.prefixes = new String[] {prefix};
        this.caseSensitivity = (caseSensitivity == null ? IOCase.SENSITIVE : caseSensitivity);
    }

    /**
     * Constructs a new Prefix file filter for any of an array of prefixes.
     * <p>
     * The array is not cloned, so could be changed after constructing the
     * instance. This would be inadvisable however.
     * 
     * @param prefixes  the prefixes to allow, must not be null
     * @throws IllegalArgumentException if the prefix array is null
     */
    public PrefixFileFilter(String[] prefixes) {
        this(prefixes, IOCase.SENSITIVE);
    }

    /**
     * Constructs a new Prefix file filter for any of an array of prefixes
     * specifying case-sensitivity.
     * <p>
     * The array is not cloned, so could be changed after constructing the
     * instance. This would be inadvisable however.
     * 
     * @param prefixes  the prefixes to allow, must not be null
     * @param caseSensitivity  how to handle case sensitivity, null means case-sensitive
     * @throws IllegalArgumentException if the prefix is null
     * @since Commons IO 1.4
     */
    public PrefixFileFilter(String[] prefixes, IOCase caseSensitivity) {
        if (prefixes == null) {
            throw new IllegalArgumentException("The array of prefixes must not be null");
        }
        this.prefixes = new String[prefixes.length];
        System.arraycopy(prefixes, 0, this.prefixes, 0, prefixes.length);
        this.caseSensitivity = (caseSensitivity == null ? IOCase.SENSITIVE : caseSensitivity);
    }

    /**
     * Constructs a new Prefix file filter for a list of prefixes.
     * 
     * @param prefixes  the prefixes to allow, must not be null
     * @throws IllegalArgumentException if the prefix list is null
     * @throws ClassCastException if the list does not contain Strings
     */
    public PrefixFileFilter(List<String> prefixes) {
        this(prefixes, IOCase.SENSITIVE);
    }

    /**
     * Constructs a new Prefix file filter for a list of prefixes
     * specifying case-sensitivity.
     * 
     * @param prefixes  the prefixes to allow, must not be null
     * @param caseSensitivity  how to handle case sensitivity, null means case-sensitive
     * @throws IllegalArgumentException if the prefix list is null
     * @throws ClassCastException if the list does not contain Strings
     * @since Commons IO 1.4
     */
    public PrefixFileFilter(List<String> prefixes, IOCase caseSensitivity) {
        if (prefixes == null) {
            throw new IllegalArgumentException("The list of prefixes must not be null");
        }
        this.prefixes = prefixes.toArray(new String[prefixes.size()]);
        this.caseSensitivity = (caseSensitivity == null ? IOCase.SENSITIVE : caseSensitivity);
    }

    /**
     * Checks to see if the filename starts with the prefix.
     * 
     * @param file  the File to check
     * @return true if the filename starts with one of our prefixes
     */
    @Override
    public boolean accept(File file) {
        String name = file.getName();
        for (String prefix : this.prefixes) {
            if (caseSensitivity.checkStartsWith(name, prefix)) {
                return true;
            }
        }
        return false;
    }
    
    /**
     * Checks to see if the filename starts with the prefix.
     * 
     * @param file  the File directory
     * @param name  the filename
     * @return true if the filename starts with one of our prefixes
     */
    @Override
    public boolean accept(File file, String name) {
        for (String prefix : prefixes) {
            if (caseSensitivity.checkStartsWith(name, prefix)) {
                return true;
            }
        }
        return false;
    }

    /**
     * Provide a String representaion of this file filter.
     *
     * @return a String representaion
     */
    @Override
    public String toString() {
        StringBuilder buffer = new StringBuilder();
        buffer.append(super.toString());
        buffer.append("(");
        if (prefixes != null) {
            for (int i = 0; i < prefixes.length; i++) {
                if (i > 0) {
                    buffer.append(",");
                }
                buffer.append(prefixes[i]);
            }
        }
        buffer.append(")");
        return buffer.toString();
    }
    
}