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/*
* Copyright (C) 2017 Google, Inc.
*
* 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.escapevelocity;
import java.util.AbstractSet;
import java.util.Arrays;
import java.util.Iterator;
/**
* An immutable set. This implementation is only suitable for sets with a small number of elements.
*
* @author emcmanus@google.com (Éamonn McManus)
*/
class ImmutableSet<E> extends AbstractSet<E> {
private final E[] elements;
private ImmutableSet(E[] elements) {
this.elements = elements;
}
@Override
public Iterator<E> iterator() {
return Arrays.asList(elements).iterator();
}
@Override
public int size() {
return elements.length;
}
@SafeVarargs
static <E> ImmutableSet<E> of(E... elements) {
int len = elements.length;
for (int i = 0; i < len - 1; i++) {
for (int j = len - 1; j > i; j--) {
if (elements[i].equals(elements[j])) {
// We want to exclude elements[j] from the final set. We can do that by copying the
// current last element in place of j (this might be j itself) and then reducing the
// size of the set.
elements[j] = elements[len - 1];
len--;
}
}
}
return new ImmutableSet<>(Arrays.copyOf(elements, len));
}
}
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