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Copy pathE21_ClassTypeCapture.java
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51 lines (49 loc) · 1.55 KB
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package generics;
import java.util.HashMap;
import java.util.Map;
import static net.mindview.util.Print.*;
//: generics/ClassTypeCapture.java
class ClassTypeCapture2 {
Map<String, Class<?>> types = new HashMap<String, Class<?>>();
public Object createNew(String typename) {
Class<?> cl = types.get(typename);
try {
return cl.newInstance();
} catch (NullPointerException e) {
// TODO Auto-generated catch block
// e.printStackTrace();
print("Not a registered typename: "+typename);
} catch (IllegalAccessException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (InstantiationException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return null;
}
public void addType(String typename, Class<?> kind) {
types.put(typename, kind);
}
}
public class E21_ClassTypeCapture<T> {
public static void main(String[] args) {
ClassTypeCapture2 ctt = new ClassTypeCapture2();
ctt.addType("Building", Building.class);
ctt.addType("House", House.class);
ctt.addType("Product", Product.class);
print(ctt.createNew("Building").getClass());
print(ctt.createNew("House").getClass());
// Product类没有无参构造器
ctt.createNew("Product");
ctt.createNew("Car");
}
} /* Output:
class generics.Building
class generics.House
java.lang.InstantiationException: generics.Product
at java.lang.Class.newInstance(Class.java:364)
at generics.ClassTypeCapture2.createNew(E21_ClassTypeCapture.java:13)
at generics.E21_ClassTypeCapture.main(E21_ClassTypeCapture.java:39)
Not a registered typename: Car
*///:~