Java 使用反射实现扩展数组

/**
 * 
 */
package freewill.reflectdemo;

import java.lang.reflect.Array;

/**
 * @author freewill
 * @desc 使用反射实现扩展数组
 * @see Core Java page196
 */
public class ArrayGrowTest {

	/**
	 * @desc bad
	 * @param a源数组
	 * @return 扩展后的数组
	 */
	static Object[] badArrayGrow(Object[] a) {
		int newLength = a.length * 11 / 10 + 10;
		Object[] newArray = new Object[newLength];
		System.arraycopy(a, 0, newArray, 0, a.length);
		return newArray;
	}

	/**
	 * @desc good
	 * @param a源数组
	 * @return 扩展后的数组
	 */
	static Object goodArrayGrow(Object[] a) {
		Class cl = a.getClass();
		if (!cl.isArray())
			return null;
		Class componentType = cl.getComponentType();
		int length = Array.getLength(a);
		int newLength = length * 11 / 10 + 10;

		Object newArray = Array.newInstance(componentType, newLength);
		System.arraycopy(a, 0, newArray, 0, length);
		return newArray;
	}

	/**
	 * 数组内容全部打印方法
	 * 
	 * @param a数组
	 */
	static void arrayPrint(Object a) {
		Class cl = a.getClass();
		if (!cl.isArray())
			return;
		Class componentType = cl.getComponentType();
		int length = Array.getLength(a);
		System.out.println(componentType.getName() + "[" + length + "]={");
		for (int i = 0; i < Array.getLength(a); i++) {
			System.out.println(Array.get(a, i) + " ");
		}
		System.out.println("}");
	}

	/**
	 * @desc Testcase
	 * @param args
	 */
	public static void main(String[] args) {
		Integer[] a = { 1, 2, 3 };
		a = (Integer[]) goodArrayGrow(a);
		arrayPrint(a);

		String[] b = { "Tom", "Dick", "Harry" };
		b = (String[]) goodArrayGrow(b);
		arrayPrint(b);

		// b = (String[]) badArrayGrow(b);
		// arrayPrint(b);
	}
}