我试图使用反射来创建匿名类的实例。但讽刺的是,我在瞬间看到了奇怪的行为。匿名类混淆的动态构造
请看看这些代码相似的片段
public class HideAndSeek {
@SuppressWarnings("unchecked")
public static void main(String[] args) throws IllegalAccessException, InstantiationException{
final String finalString = "I'm final :)";
Object object2 = new Object(){
{
System.out.println("Instance initializing block");
System.out.println(finalString);
}
private void hiddenMethod() {
System.out.println("Use reflection to find me :)");
}
};
Object tmp = object2.getClass().newInstance();
}
}
此代码的工作很好,输出预计
Instance initializing block
I'm final :)
Instance initializing block
I'm final :)
这个我决定用简单的方式来改变代码后(刚添加java.util.Calendar)
import java.util.Calendar;
public class HideAndSeek {
@SuppressWarnings("unchecked")
public static void main(String[] args) throws IllegalAccessException, InstantiationException{
final String finalString = "I'm final :)";
final Calendar calendar = Calendar.getInstance();
System.out.println(calendar.getTime().toString()); //works well
Object object2 = new Object(){
{
System.out.println("Instance initializing block");
System.out.println(finalString);
//simply added this line
System.out.println(calendar.getTime().toString());
}
private void hiddenMethod() {
System.out.println("Use reflection to find me :)");
}
};
Object tmp = object2.getClass().newInstance();
}
}
这里是输出,我得到了:
Wed Aug 17 02:08:47 EEST 2011
Instance initializing block
I'm final :)
Wed Aug 17 02:08:47 EEST 2011
Exception in thread "main" java.lang.InstantiationException: HideAndSeek$1
at java.lang.Class.newInstance0(Unknown Source)
at java.lang.Class.newInstance(Unknown Source)
at HideAndSeek.main(HideAndSeek.java:29)
如您所见 - 新实例尚未创建。
有没有人可以解释我,这种变化的原因?
谢谢
如果日历instnace不是最终的呢? – SJuan76
@ SJuan76。 ...那么你就不能将它传递给匿名的内部类。 –