转载自  Java编程：Java的反射机制中的 getComponentType() 方法

 

Java 中所有的类都继承自 Object，数组本身也是一个 Class，如果我们能够得到数据的 Class 对象，那么我们可以通过反射生成数组对象。

在Java的反射机制中，通过 数组的 class 对象的getComponentType()方法可以取得一个数组的Class对象， 通过Array.newInstance()可以反射生成数组对象，看示例代码：

package com.ips.reflect;import java.lang.reflect.Array;public class GetComponentType {public static void main(String [] args){Class<char[]>  aa = (Class<char[]>) char.class.getComponentType();System.out.println("the componentType of the char is :" + char.class.getComponentType());System.out.println("the componentType of the char[] is :" + char[].class.getComponentType());System.out.println("the componentType of the String is :" + String.class.getComponentType());System.out.println("the componentType of the String[] is :" + String[].class.getComponentType());System.out.println("the componentType of the int is :" + int.class.getComponentType());System.out.println("the componentType of the int[] is :" + int[].class.getComponentType());System.out.println("the componentType of the Integer is :" + Integer.class.getComponentType());System.out.println("the componentType of the Integer[] is :" + Integer[].class.getComponentType());try {char c = (char)Array.newInstance(char.class.getComponentType(), 10);} catch (Exception e) {e.printStackTrace();}char[] charArray = (char [])Array.newInstance(char[].class.getComponentType(), 100);System.out.println("the length of the charArray is :" + charArray.length);try {String c = (String)Array.newInstance(String.class.getComponentType(), 10);} catch (Exception e) {e.printStackTrace();}String[] strArray = (String [])Array.newInstance(String[].class.getComponentType(), 10);System.out.println("the length of the strArray is :" + strArray.length);}
}

执行结果：

the componentType of the char is :null 
the componentType of the char[] is :char 
the componentType of the String is :null 
the componentType of the String[] is :class java.lang.String 
the componentType of the int is :null 
the componentType of the int[] is :int 
the componentType of the Integer is :null 
the componentType of the Integer[] is :class java.lang.Integer 
java.lang.NullPointerException 
at java.lang.reflect.Array.newArray(Native Method) 
at java.lang.reflect.Array.newInstance(Array.java:70) 
at com.ips.reflect.GetComponentType.main(GetComponentType.java:23) 
the length of the charArray is :100 
java.lang.NullPointerException 
at java.lang.reflect.Array.newArray(Native Method) 
at java.lang.reflect.Array.newInstance(Array.java:70) 
at com.ips.reflect.GetComponentType.main(GetComponentType.java:31) 
the length of the strArray is :10

通过以上代码我们可以发现：

1. 非数组类型无法通过getComponentType()获取到相应的 Class 对象；
2. 非数组类型无法通过(String [])Array.newInstance(String[].class.getComponentType(), 10)方法反射生成数组对象，因为获取不到 Class 对象；
3. 无论基本数据类型（byte short int long float double char boolean）的数组还是引用数据类型（Integer String 等）的数组，都可以通过getComponentType()获取到相应的 Class 对象，都可以通过(String [])Array.newInstance(String[].class.getComponentType(), 10)方法反射生成数组对象。