All Downloads are FREE. Search and download functionalities are using the official Maven repository.

com.google.common.collect.ObjectArrays Maven / Gradle / Ivy

Go to download

Guava is a suite of core and expanded libraries that include utility classes, google's collections, io classes, and much much more.

There is a newer version: 33.3.0-jre
Show newest version
/*
 * Copyright (C) 2007 The Guava 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
 *
 * 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.common.collect;

import static com.google.common.base.Preconditions.checkPositionIndexes;

import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.lang.reflect.Array;
import java.util.Arrays;
import java.util.Collection;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Static utility methods pertaining to object arrays.
 *
 * @author Kevin Bourrillion
 * @since 2.0
 */
@GwtCompatible(emulated = true)
public final class ObjectArrays {

  private ObjectArrays() {}

  /**
   * Returns a new array of the given length with the specified component type.
   *
   * @param type the component type
   * @param length the length of the new array
   */
  @GwtIncompatible // Array.newInstance(Class, int)
  @SuppressWarnings("unchecked")
  public static  T[] newArray(Class type, int length) {
    return (T[]) Array.newInstance(type, length);
  }

  /**
   * Returns a new array of the given length with the same type as a reference array.
   *
   * @param reference any array of the desired type
   * @param length the length of the new array
   */
  public static  T[] newArray(T[] reference, int length) {
    return Platform.newArray(reference, length);
  }

  /**
   * Returns a new array that contains the concatenated contents of two arrays.
   *
   * @param first the first array of elements to concatenate
   * @param second the second array of elements to concatenate
   * @param type the component type of the returned array
   */
  @GwtIncompatible // Array.newInstance(Class, int)
  public static  T[] concat(T[] first, T[] second, Class type) {
    T[] result = newArray(type, first.length + second.length);
    System.arraycopy(first, 0, result, 0, first.length);
    System.arraycopy(second, 0, result, first.length, second.length);
    return result;
  }

  /**
   * Returns a new array that prepends {@code element} to {@code array}.
   *
   * @param element the element to prepend to the front of {@code array}
   * @param array the array of elements to append
   * @return an array whose size is one larger than {@code array}, with {@code element} occupying
   *     the first position, and the elements of {@code array} occupying the remaining elements.
   */
  public static  T[] concat(@Nullable T element, T[] array) {
    T[] result = newArray(array, array.length + 1);
    result[0] = element;
    System.arraycopy(array, 0, result, 1, array.length);
    return result;
  }

  /**
   * Returns a new array that appends {@code element} to {@code array}.
   *
   * @param array the array of elements to prepend
   * @param element the element to append to the end
   * @return an array whose size is one larger than {@code array}, with the same contents as {@code
   *     array}, plus {@code element} occupying the last position.
   */
  public static  T[] concat(T[] array, @Nullable T element) {
    T[] result = Arrays.copyOf(array, array.length + 1);
    result[array.length] = element;
    return result;
  }

  /**
   * Returns an array containing all of the elements in the specified collection; the runtime type
   * of the returned array is that of the specified array. If the collection fits in the specified
   * array, it is returned therein. Otherwise, a new array is allocated with the runtime type of the
   * specified array and the size of the specified collection.
   *
   * 

If the collection fits in the specified array with room to spare (i.e., the array has more * elements than the collection), the element in the array immediately following the end of the * collection is set to {@code null}. This is useful in determining the length of the collection * only if the caller knows that the collection does not contain any null elements. * *

This method returns the elements in the order they are returned by the collection's * iterator. * *

TODO(kevinb): support concurrently modified collections? * * @param c the collection for which to return an array of elements * @param array the array in which to place the collection elements * @throws ArrayStoreException if the runtime type of the specified array is not a supertype of * the runtime type of every element in the specified collection */ static T[] toArrayImpl(Collection c, T[] array) { int size = c.size(); if (array.length < size) { array = newArray(array, size); } fillArray(c, array); if (array.length > size) { array[size] = null; } return array; } /** * Implementation of {@link Collection#toArray(Object[])} for collections backed by an object * array. the runtime type of the returned array is that of the specified array. If the collection * fits in the specified array, it is returned therein. Otherwise, a new array is allocated with * the runtime type of the specified array and the size of the specified collection. * *

If the collection fits in the specified array with room to spare (i.e., the array has more * elements than the collection), the element in the array immediately following the end of the * collection is set to {@code null}. This is useful in determining the length of the collection * only if the caller knows that the collection does not contain any null elements. */ static T[] toArrayImpl(Object[] src, int offset, int len, T[] dst) { checkPositionIndexes(offset, offset + len, src.length); if (dst.length < len) { dst = newArray(dst, len); } else if (dst.length > len) { dst[len] = null; } System.arraycopy(src, offset, dst, 0, len); return dst; } /** * Returns an array containing all of the elements in the specified collection. This method * returns the elements in the order they are returned by the collection's iterator. The returned * array is "safe" in that no references to it are maintained by the collection. The caller is * thus free to modify the returned array. * *

This method assumes that the collection size doesn't change while the method is running. * *

TODO(kevinb): support concurrently modified collections? * * @param c the collection for which to return an array of elements */ static Object[] toArrayImpl(Collection c) { return fillArray(c, new Object[c.size()]); } /** * Returns a copy of the specified subrange of the specified array that is literally an Object[], * and not e.g. a {@code String[]}. */ static Object[] copyAsObjectArray(Object[] elements, int offset, int length) { checkPositionIndexes(offset, offset + length, elements.length); if (length == 0) { return new Object[0]; } Object[] result = new Object[length]; System.arraycopy(elements, offset, result, 0, length); return result; } @CanIgnoreReturnValue private static Object[] fillArray(Iterable elements, Object[] array) { int i = 0; for (Object element : elements) { array[i++] = element; } return array; } /** Swaps {@code array[i]} with {@code array[j]}. */ static void swap(Object[] array, int i, int j) { Object temp = array[i]; array[i] = array[j]; array[j] = temp; } @CanIgnoreReturnValue static Object[] checkElementsNotNull(Object... array) { return checkElementsNotNull(array, array.length); } @CanIgnoreReturnValue static Object[] checkElementsNotNull(Object[] array, int length) { for (int i = 0; i < length; i++) { checkElementNotNull(array[i], i); } return array; } // We do this instead of Preconditions.checkNotNull to save boxing and array // creation cost. @CanIgnoreReturnValue static Object checkElementNotNull(Object element, int index) { if (element == null) { throw new NullPointerException("at index " + index); } return element; } }





© 2015 - 2024 Weber Informatics LLC | Privacy Policy