org.microbean.assign.ClassesThenInterfacesElementKindComparator Maven / Gradle / Ivy
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/* -*- mode: Java; c-basic-offset: 2; indent-tabs-mode: nil; coding: utf-8-unix -*-
*
* Copyright © 2025 microBean™.
*
* 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 org.microbean.assign;
import java.util.Comparator;
import javax.lang.model.element.ElementKind;
/**
* A {@link Comparator} establishing a partial order over {@link ElementKind}s such that {@linkplain
* ElementKind#isClass() classes} precede {@linkplain ElementKind#isInterface() interfaces}.
*
* @author Laird Nelson
*
* @see #compare(ElementKind, ElementKind)
*/
public final class ClassesThenInterfacesElementKindComparator implements Comparator {
/**
* The sole instance of this class.
*/
public static final ClassesThenInterfacesElementKindComparator INSTANCE = new ClassesThenInterfacesElementKindComparator();
private ClassesThenInterfacesElementKindComparator() {
super();
}
/**
* Compares the two {@link ElementKind}s and returns the result.
*
* If {@code k0 == k1}, returns {@code 0}.
*
* If {@code k0} is {@code null} and {@code k1} is not, returns a positive value.
*
* If {@code k0} {@linkplain ElementKind#isClass() is a class} and {@code k1} {@linkplain ElementKind#isInterface()
* is an interface}, returns a negative value.
*
* If {@code k0} {@linkplain ElementKind#isInterface() is an interface} and {@code k1} {@linkplain
* ElementKind#isClass() is a class}, returns a positive value.
*
* Returns {@code 0} in all other cases.
*
* @param k0 an {@link ElementKind}; may be {@code null}
*
* @param k1 an {@link ElementKind}; may be {@code null}
*
* @return a comparison result
*
* @see ElementKind#isClass()
*
* @see ElementKind#isInterface()
*/
@Override // Comparator
public final int compare(final ElementKind k0, final ElementKind k1) {
if (k0 == k1) {
return 0;
} else if (k0 == null) {
return 1;
} else if (k1 == null) {
return -1;
} else if (k0.isClass() && k1.isInterface()) {
return -1;
} else if (k0.isInterface() && k1.isClass()) {
return 1;
} else {
return 0;
}
}
}