【Java面向对象】08 反射，反射泛型数组（2）

public void reflectArrayCreatedTest() {
    try {
        String[] a1 = {"a", "b"};
        String[] r1 = (String[]) badCopy(a1, 2);
        System.out.println(Arrays.toString(r1));
    } catch (ClassCastException e) {
        e.printStackTrace();
    }
    System.out.println("=======");

    // String
    String[] a2 = {"a", "b"};
    String[] r2 = (String[]) goodCopy(a2, 2);
    System.out.println(Arrays.toString(r2)); // [a, b]

    // int
    int[] a3 = {1, 2};
    int[] r3 = (int[]) goodCopy(a3, 2);
    System.out.println(Arrays.toString(r3)); // [1, 2]
}


public static Object[] badCopy(Object[] a, int newLength) {
    Object[] newArray = new Object[newLength];
    System.arraycopy(a, 0, newArray, 0, Math.min(a.length, newLength));
    return newArray;
}


public static Object goodCopy(Object a, int newLength) {
    Class cl = a.getClass();
    if (!cl.isArray()) return null;
    // 确定数组类型
    Class componentType = cl.getComponentType();
    int length = Array.getLength(a);
    // 创建指定类型数组
    Object newArray = Array.newInstance(componentType, newLength);
    System.arraycopy(a, 0, newArray, 0, Math.min(length, newLength));
    return newArray;
}