org.springframework.util.comparator.InstanceComparator Maven / Gradle / Ivy
/*
* Copyright 2002-2019 the original author or 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
*
* https://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.springframework.util.comparator;
import java.util.Comparator;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
/**
* Compares objects based on an arbitrary class order. Allows objects to be sorted based
* on the types of class that they inherit, for example: this comparator can be used to
* sort a list {@code Number}s such that {@code Long}s occur before {@code Integer}s.
*
* Only the specified {@code instanceOrder} classes are considered during comparison.
* If two objects are both instances of the ordered type this comparator will return a
* {@code 0}. Consider combining with {@link Comparator#thenComparing(Comparator)}
* if additional sorting is required.
*
* @author Phillip Webb
* @since 3.2
* @param the type of objects that may be compared by this comparator
* @see Comparator#thenComparing(Comparator)
*/
public class InstanceComparator implements Comparator {
private final Class[] instanceOrder;
/**
* Create a new {@link InstanceComparator} instance.
* @param instanceOrder the ordered list of classes that should be used when comparing
* objects. Classes earlier in the list will be given a higher priority.
*/
public InstanceComparator(Class... instanceOrder) {
Assert.notNull(instanceOrder, "'instanceOrder' array must not be null");
this.instanceOrder = instanceOrder;
}
@Override
public int compare(T o1, T o2) {
int i1 = getOrder(o1);
int i2 = getOrder(o2);
return (Integer.compare(i1, i2));
}
private int getOrder(@Nullable T object) {
if (object != null) {
for (int i = 0; i < this.instanceOrder.length; i++) {
if (this.instanceOrder[i].isInstance(object)) {
return i;
}
}
}
return this.instanceOrder.length;
}
}