Arrays是数组的工具类，其提供了许多的工具类方法，下面将分别对其一一介绍。
（一）copyOf方法
Arrays当中的copyOf方法主要分为两种类型，一种是对primitive类型数组的复制，一种是对引用类型数组的复制，其最终都是调用System.arraycopy方法。分别将各种类型写成不同的方法，这样做一是充分利用JAVA面向对象多态的思路，二是避免因类型不匹配时出现异常,例子如下：
基本数据类型数组的复制，首先new出一个指定长度的数组，然后调用System.arraycopy方法进行复制。
/** * Copies the specified array, truncating or padding with zeros (if necessary) * so the copy has the specified length. For all indices that are * valid in both the original array and the copy, the two arrays will * contain identical values. For any indices that are valid in the * copy but not the original, the copy will contain <tt>0</tt>. * Such indices will exist if and only if the specified length * is greater than that of the original array. * * @param original the array to be copied * @param newLength the length of the copy to be returned * @return a copy of the original array, truncated or padded with zeros * to obtain the specified length * @throws NegativeArraySizeException if <tt>newLength</tt> is negative * @throws NullPointerException if <tt>original</tt> is null * @since 1.6 */ public static int[] copyOf(int[] original, int newLength) { int[] copy = new int[newLength]; System.arraycopy(original, 0, copy, 0, Math.min(original.length, newLength)); return copy; }