Arrays数组工具类

Arrays的拷贝CopyOf（）；

把一个就数组拷贝到一个新的数组中。

public class ArrayDemo {
    public static void main(String[] args) {
        int[] arr1 = {1, 2, 3, 4, 5}; 
        int[] arr2 = Arrays.copyOf(arr1, 5);
        int[] arr3 = Arrays.copyOf(arr1, 10);
        for(int i = 0; i < arr2.length; i++) 
            System.out.print(arr2[i] + " "); 
            System.out.println();
        for(int i = 0; i < arr3.length; i++) 
            System.out.print(arr3[i] + " ");
    }
} 

运行结果

1 2 3 4 5 
1 2 3 4 5 0 0 0 0 0

底层方法是

 @SuppressWarnings("unchecked")
    public static <T> T[] copyOf(T[] original, int newLength) {
        return (T[]) copyOf(original, newLength, original.getClass());
    }

 @SuppressWarnings("unchecked")
    public static <T> T[] copyOf(T[] original, int newLength) {
        return (T[]) copyOf(original, newLength, original.getClass());
    }

  public static native void arraycopy(Object src,  int  srcPos,
                                        Object dest, int destPos,
                                        int length);