Arrays类

Arrays类

一、简介

java.util.Arrays

java用于管理数组的类。

二、常用方法

1.Arrays.fill()

• fill(int[] a, int val)
  将指定的val值赋值给数组a的每个元素。

/**
     * Assigns the specified int value to each element of the specified array
     * of ints.
     *
     * @param a the array to be filled
     * @param val the value to be stored in all elements of the array
     */
    public static void fill(int[] a, int val) {
        for (int i = 0, len = a.length; i < len; i++)
            a[i] = val;
    }

• fill(int[] a, int fromIndex, int toIndex, int val)
  将指定的val值赋值给数组a[fromIndex]到a[toIndex]

 /**
     * Assigns the specified int value to each element of the specified
     * range of the specified array of ints.  The range to be filled
     * extends from index <tt>fromIndex</tt>, inclusive, to index
     * <tt>toIndex</tt>, exclusive.  (If <tt>fromIndex==toIndex</tt>, the
     * range to be filled is empty.)
     *
     * @param a the array to be filled
     * @param fromIndex the index of the first element (inclusive) to be
     *        filled with the specified value
     * @param toIndex the index of the last element (exclusive) to be
     *        filled with the specified value
     * @param val the value to be stored in all elements of the array
     * @throws IllegalArgumentException if <tt>fromIndex &gt; toIndex</tt>
     * @throws ArrayIndexOutOfBoundsException if <tt>fromIndex &lt; 0</tt> or
     *         <tt>toIndex &gt; a.length</tt>
     */
    public static void fill(int[] a, int fromIndex, int toIndex, int val) {
        rangeCheck(a.length, fromIndex, toIndex);//检查数组下标的输入是否正确;
        for (int i = fromIndex; i < toIndex; i++)
            a[i] = val;
    }

2. Arrays.asLink()

返回包含参数数组中所有元素的列表。

/**
     * Returns a fixed-size list backed by the specified array.  (Changes to
     * the returned list "write through" to the array.)  This method acts
     * as bridge between array-based and collection-based APIs, in
     * combination with {@link Collection#toArray}.  The returned list is
     * serializable and implements {@link RandomAccess}.
     *
     * <p>This method also provides a convenient way to create a fixed-size
     * list initialized to contain several elements:
     * <pre>
     *     List&lt;String&gt; stooges = Arrays.asList("Larry", "Moe", "Curly");
     * </pre>
     *
     * @param <T> the class of the objects in the array
     * @param a the array by which the list will be backed
     * @return a list view of the specified array
     */
    @SafeVarargs
    @SuppressWarnings("varargs")
    public static <T> List<T> asList(T... a) {
        return new ArrayList<>(a);
    }