Java数组的复制Arrays.copyOf()和System.arraycopy()函数

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

public static <T,U> T[] copyOf(U[] original, int newLength, Class<? extends T[]> newType) {  
        T[] copy = ((Object)newType == (Object)Object[].class)  
            ? (T[]) new Object[newLength]  
            : (T[]) Array.newInstance(newType.getComponentType(), newLength);  
        System.arraycopy(original, 0, copy, 0,  
                         Math.min(original.length, newLength));  
        return copy;  
    }  
public static <T> T[] copyOf(T[] original, int newLength) {  
    return (T[]) copyOf(original, newLength, original.getClass());  
}