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The Apache Commons IO library contains utility classes, stream implementations, file filters,
file comparators, endian transformation classes, and much more.
/*
* 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.ArrayList;
import java.util.Comparator;
import java.util.List;
/**
* Compare two files using a set of delegate file {@link Comparator}.
*
* This comparator can be used to sort lists or arrays of files
* by combining a number other comparators.
*
* Example of sorting a list of files by type (i.e. directory or file)
* and then by name:
*
* CompositeFileComparator comparator =
* new CompositeFileComparator(
* (AbstractFileComparator) DirectoryFileComparator.DIRECTORY_COMPARATOR,
* (AbstractFileComparator) NameFileComparator.NAME_COMPARATOR);
* List<File> list = ...
* comparator.sort(list);
*
*
* @since 2.0
*/
public class CompositeFileComparator extends AbstractFileComparator implements Serializable {
private static final long serialVersionUID = -2224170307287243428L;
private static final Comparator[] NO_COMPARATORS = {};
private final Comparator[] delegates;
/**
* Create a composite comparator for the set of delegate comparators.
*
* @param delegates The delegate file comparators
*/
@SuppressWarnings("unchecked") // casts 1 & 2 must be OK because types are already correct
public CompositeFileComparator(final Comparator... delegates) {
if (delegates == null) {
this.delegates = (Comparator[]) NO_COMPARATORS;//1
} else {
this.delegates = (Comparator[]) new Comparator[delegates.length];//2
System.arraycopy(delegates, 0, this.delegates, 0, delegates.length);
}
}
/**
* Create a composite comparator for the set of delegate comparators.
*
* @param delegates The delegate file comparators
*/
@SuppressWarnings("unchecked") // casts 1 & 2 must be OK because types are already correct
public CompositeFileComparator(final Iterable> delegates) {
if (delegates == null) {
this.delegates = (Comparator[]) NO_COMPARATORS; //1
} else {
final List> list = new ArrayList<>();
for (final Comparator comparator : delegates) {
list.add(comparator);
}
this.delegates = (Comparator[]) list.toArray(new Comparator[list.size()]); //2
}
}
/**
* Compare 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) {
int result = 0;
for (final Comparator delegate : delegates) {
result = delegate.compare(file1, file2);
if (result != 0) {
break;
}
}
return result;
}
/**
* 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();
}
}