Java Reflect 反射 学习笔记3 操作

       Java Reflect编写 通用数组扩展类
 
package com.accp.array;

import java.lang.reflect.Array;

public class GrowArrayTest {
public static void main(String[] args) {
Integer[] array = {1,2,3,4}; //通用扩展
arrayPrint(array);
array = (Integer[])goodArrayGrow(array);
arrayPrint(array);


String[] str = {"xw","xz"};
arrayPrint(str);
str = (String[])badArrayGrow(str); //会报ClassCastException异常,无法将Object转换成String类型
arrayPrint(str);

int[] a = null;
goodArrayGrow(a);
arrayPrint(a);

}

public static Object goodArrayGrow(Object o) {
Class clazz = o.getClass(); //得到类型信息
if (!clazz.isArray())
return null;

Class type = clazz.getComponentType(); //得到o的类型
int newLength = Array.getLength(o) * 11 / 10 + 10;

Object newArray = Array.newInstance(type, newLength); //创建一个新的Array, type = clazz.getComponentype()
System.arraycopy(o, 0, newArray, 0, Array.getLength(o));
return newArray;
}

public static Object[] badArrayGrow(Object[] o){
int newLength = o.length * 11 /10 +10;
Object[] newArray = new Object[o.length];
System.arraycopy(o, 0, newArray, 0, o.length);
return newArray;
}

public static void arrayPrint(Object a) { // 遍历输出数组值


Class clazz = a.getClass(); // 得到类型信息
if (!clazz.isArray())
return;

Class type = clazz.getComponentType(); // 得到类型
Integer length = Array.getLength(a); // 得到长度

System.out.print(type.getName() + "[" + length + "]={"); // 格式化输出

for (int i = 0; i < Array.getLength(a); i++)
System.out.print(Array.get(a, i) + " ");
System.out.println("}");

}
}