/*
* Copyright DataStax, 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.datastax.oss.driver.internal.core.util;
import edu.umd.cs.findbugs.annotations.NonNull;
import java.util.concurrent.ThreadLocalRandom;
public class ArrayUtils {
public static <ElementT> void swap(@NonNull ElementT[] elements, int i, int j) {
if (i != j) {
ElementT tmp = elements[i];
elements[i] = elements[j];
elements[j] = tmp;
}
}
Moves an element towards the beginning of the array, shifting all the intermediary elements to the right (no-op if targetIndex >= sourceIndex
). /**
* Moves an element towards the beginning of the array, shifting all the intermediary elements to
* the right (no-op if {@code targetIndex >= sourceIndex}).
*/
public static <ElementT> void bubbleUp(
@NonNull ElementT[] elements, int sourceIndex, int targetIndex) {
for (int i = sourceIndex; i > targetIndex; i--) {
swap(elements, i, i - 1);
}
}
Moves an element towards the end of the array, shifting all the intermediary elements to the left (no-op if targetIndex <= sourceIndex
). /**
* Moves an element towards the end of the array, shifting all the intermediary elements to the
* left (no-op if {@code targetIndex <= sourceIndex}).
*/
public static <ElementT> void bubbleDown(
@NonNull ElementT[] elements, int sourceIndex, int targetIndex) {
for (int i = sourceIndex; i < targetIndex; i++) {
swap(elements, i, i + 1);
}
}
Shuffles the first n elements of the array in-place.
Params: - elements – the array to shuffle.
- n – the number of elements to shuffle; must be
<= elements.length
.
See Also:
/**
* Shuffles the first n elements of the array in-place.
*
* @param elements the array to shuffle.
* @param n the number of elements to shuffle; must be {@code <= elements.length}.
* @see <a
* href="https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle#The_modern_algorithm">Modern
* Fisher-Yates shuffle</a>
*/
public static <ElementT> void shuffleHead(@NonNull ElementT[] elements, int n) {
shuffleHead(elements, n, ThreadLocalRandom.current());
}
Shuffles the first n elements of the array in-place.
Params: - elements – the array to shuffle.
- n – the number of elements to shuffle; must be
<= elements.length
. - random – the
ThreadLocalRandom
instance to use. This is mainly intended to facilitate tests.
See Also:
/**
* Shuffles the first n elements of the array in-place.
*
* @param elements the array to shuffle.
* @param n the number of elements to shuffle; must be {@code <= elements.length}.
* @param random the {@link ThreadLocalRandom} instance to use. This is mainly intended to
* facilitate tests.
* @see <a
* href="https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle#The_modern_algorithm">Modern
* Fisher-Yates shuffle</a>
*/
public static <ElementT> void shuffleHead(
@NonNull ElementT[] elements, int n, @NonNull ThreadLocalRandom random) {
if (n > elements.length) {
throw new ArrayIndexOutOfBoundsException(
String.format(
"Can't shuffle the first %d elements, there are only %d", n, elements.length));
}
if (n > 1) {
for (int i = n - 1; i > 0; i--) {
int j = random.nextInt(i + 1);
swap(elements, i, j);
}
}
}
Rotates the elements in the specified range by the specified amount (round-robin). /** Rotates the elements in the specified range by the specified amount (round-robin). */
public static <ElementT> void rotate(
@NonNull ElementT[] elements, int startIndex, int length, int amount) {
if (length >= 2) {
amount = amount % length;
// Repeatedly shift by 1. This is not the most time-efficient but the array will typically be
// small so we don't care, and this avoids allocating a temporary buffer.
for (int i = 0; i < amount; i++) {
bubbleDown(elements, startIndex, startIndex + length - 1);
}
}
}
}