我有一个抽象类:
public abstract class Room {
}
以及编译时未知的继承类,例如:
public class MagicRoom extends Room {
public MagicRoom(){
System.out.println("Creating a MagicRoom.");
}
public String magic = "";
}
或者:
public class Dungeon extends Room {
public Dungeon(){
System.out.println("Creating a Dungeon");
}
public String keeper = "";
}
我有一个类,我将从中创建这些类的实例:
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
public class MazeGame {
public static Room makeRoom(Class roomClass)
throws IllegalArgumentException, InstantiationException,
IllegalAccessException, InvocationTargetException,
SecurityException, NoSuchMethodException{
Constructor c = roomClass.getConstructor();
return c.newInstance();
}
}
makeRoom 是我尝试创建一个从 Room 继承的类,该类在编译时我不知道其类型,但我不确定将什么作为其返回类型而不是 Room。因为 makeRoom 返回一个 Room,所以如果我尝试使用属于继承类的字段,则会出现异常:
import java.lang.reflect.InvocationTargetException;
public class FactoryTest {
public static void main(String[] args)
throws IllegalArgumentException, SecurityException,
InstantiationException, IllegalAccessException,
InvocationTargetException, NoSuchMethodException{
MazeGame game = new MazeGame();
Room magicRoom = MazeGame.makeRoom(MagicRoom.class);
/*
* Exception in thread "main" java.lang.Error: Unresolved compilation problem:
* magic cannot be resolved or is not a field
*/
magicRoom.magic = "a";
}
}
最佳答案
使该方法通用:
public static <T extends Room> T makeRoom(Class<T> roomClass)
throws IllegalArgumentException, InstantiationException,
IllegalAccessException, InvocationTargetException,
SecurityException, NoSuchMethodException{
// This is enough, if you have 0-arg constructor in all your subclasses
return roomClass.newInstance();
}
然后像这样调用它:
MagicRoom magicRoom = MazeGame.makeRoom(MagicRoom.class);
关于java - 创建编译时未知的类的实例,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/21632979/