guava/src/com/google/common/io/PatternFilenameFilter.java


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/*
 * Copyright (C) 2006 The Guava Authors
 *
 * Licensed 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.google.common.io;

import com.google.common.annotations.Beta;
import com.google.common.base.Preconditions;

import java.io.File;
import java.io.FilenameFilter;
import java.util.regex.Pattern;
import java.util.regex.PatternSyntaxException;

import javax.annotation.Nullable;

/**
 * File name filter that only accepts files matching a regular expression. This class is thread-safe
 * and immutable.
 *
 * @author Apple Chow
 * @since 1.0
 */
@Beta
public final class PatternFilenameFilter implements FilenameFilter {

  private final Pattern pattern;

  /**
   * Constructs a pattern file name filter object.
   * @param patternStr the pattern string on which to filter file names
   *
   * @throws PatternSyntaxException if pattern compilation fails (runtime)
   */
  public PatternFilenameFilter(String patternStr) {
    this(Pattern.compile(patternStr));
  }

  /**
   * Constructs a pattern file name filter object.
   * @param pattern the pattern on which to filter file names
   */
  public PatternFilenameFilter(Pattern pattern) {
    this.pattern = Preconditions.checkNotNull(pattern);
  }

  @Override public boolean accept(@Nullable File dir, String fileName) {
    return pattern.matcher(fileName).matches();
  }
}