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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.AbstractList;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;
/**
* An immutable list.
*
* @author emcmanus@google.com (Éamonn McManus)
*/
class ImmutableList<E> extends AbstractList<E> {
private static final ImmutableList<?> EMPTY = new ImmutableList<>(new Object[0]);
private final E[] elements;
private ImmutableList(E[] elements) {
this.elements = elements;
}
@Override
public Iterator<E> iterator() {
return Arrays.asList(elements).iterator();
}
@Override
public E get(int index) {
if (index < 0 || index >= elements.length) {
throw new IndexOutOfBoundsException(String.valueOf(index));
}
return elements[index];
}
@Override
public int size() {
return elements.length;
}
static <E> ImmutableList<E> of() {
@SuppressWarnings("unchecked")
ImmutableList<E> empty = (ImmutableList<E>) EMPTY;
return empty;
}
@SafeVarargs
static <E> ImmutableList<E> of(E... elements) {
return new ImmutableList<>(elements.clone());
}
static <E> ImmutableList<E> copyOf(List<E> list) {
@SuppressWarnings("unchecked")
E[] elements = (E[]) new Object[list.size()];
list.toArray(elements);
return new ImmutableList<>(elements);
}
static <E> Builder<E> builder() {
return new Builder<E>();
}
static class Builder<E> {
private final List<E> list = new ArrayList<>();
void add(E element) {
list.add(element);
}
ImmutableList<E> build() {
if (list.isEmpty()) {
return ImmutableList.of();
}
@SuppressWarnings("unchecked")
E[] elements = (E[]) new Object[list.size()];
list.toArray(elements);
return new ImmutableList<>(elements);
}
}
}
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