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/*
* 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.comparator;
import java.io.File;
import java.io.Serializable;
import java.util.Comparator;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;
/**
* Compare two files using a set of delegate file {@link Comparator}.
* <p>
* This comparator can be used to sort lists or arrays of files by combining a number of other comparators.
* <p>
* Example of sorting a list of files by type (i.e. directory or file) and then by name:
*
* <pre>
* CompositeFileComparator comparator = new CompositeFileComparator(
* DirectoryFileComparator.DIRECTORY_COMPARATOR,
* NameFileComparator.NAME_COMPARATOR);
* List<File> list = ...
* comparator.sort(list);
* </pre>
* <h2>Deprecating Serialization</h2>
* <p>
* <em>Serialization is deprecated and will be removed in 3.0.</em>
* </p>
*
* @since 2.0
*/
public class CompositeFileComparator extends AbstractFileComparator implements Serializable {
private static final Comparator<?>[] EMPTY_COMPARATOR_ARRAY = {};
private static final long serialVersionUID = -2224170307287243428L;
private final Comparator<File>[] delegates;
/**
* Constructs a composite comparator for the set of delegate comparators.
*
* @param delegates The delegate file comparators
*/
public CompositeFileComparator(@SuppressWarnings("unchecked") final Comparator<File>... delegates) {
this.delegates = delegates == null ? emptyArray() : delegates.clone();
}
/**
* Constructs a composite comparator for the set of delegate comparators.
*
* @param delegates The delegate file comparators
*/
public CompositeFileComparator(final Iterable<Comparator<File>> delegates) {
this.delegates = delegates == null ? emptyArray() : StreamSupport.stream(delegates.spliterator(), false).toArray(Comparator[]::new);
}
/**
* Compares the two files using delegate comparators.
*
* @param file1 The first file to compare
* @param file2 The second file to compare
* @return the first non-zero result returned from the delegate comparators or zero.
*/
@Override
public int compare(final File file1, final File file2) {
return Stream.of(delegates).map(delegate -> delegate.compare(file1, file2)).filter(r -> r != 0).findFirst().orElse(0);
}
@SuppressWarnings("unchecked") // types are already correct
private Comparator<File>[] emptyArray() {
return (Comparator<File>[]) EMPTY_COMPARATOR_ARRAY;
}
/**
* String representation of this file comparator.
*
* @return String representation of this file comparator
*/
@Override
public String toString() {
final StringBuilder builder = new StringBuilder();
builder.append(super.toString());
builder.append('{');
for (int i = 0; i < delegates.length; i++) {
if (i > 0) {
builder.append(',');
}
builder.append(delegates[i]);
}
builder.append('}');
return builder.toString();
}
}
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