我怎样才能做到这一点呢?
public class GenericClass<T>
{
public Type getMyType()
{
//How do I return the type of T?
}
}
到目前为止,我所尝试的一切总是返回Object类型,而不是使用的特定类型。
我怎样才能做到这一点呢?
public class GenericClass<T>
{
public Type getMyType()
{
//How do I return the type of T?
}
}
到目前为止,我所尝试的一切总是返回Object类型,而不是使用的特定类型。
当前回答
如果你有这样一个类:
public class GenericClass<T> {
private T data;
}
T变量,那么你可以打印T名称:
System.out.println(data.getClass().getSimpleName()); // "String", "Integer", etc.
其他回答
我不认为你可以,Java在编译时使用类型擦除,这样你的代码就可以与在泛型之前创建的应用程序和库兼容。
来自Oracle文档:
Type Erasure Generics were introduced to the Java language to provide tighter type checks at compile time and to support generic programming. To implement generics, the Java compiler applies type erasure to: Replace all type parameters in generic types with their bounds or Object if the type parameters are unbounded. The produced bytecode, therefore, contains only ordinary classes, interfaces, and methods. Insert type casts if necessary to preserve type safety. Generate bridge methods to preserve polymorphism in extended generic types. Type erasure ensures that no new classes are created for parameterized types; consequently, generics incur no runtime overhead.
http://docs.oracle.com/javase/tutorial/java/generics/erasure.html
你不能。如果向类中添加类型为T的成员变量(甚至不需要初始化它),则可以使用它来恢复类型。
这里有一个方法,我用过一两次:
public abstract class GenericClass<T>{
public abstract Class<T> getMyType();
}
随着
public class SpecificClass extends GenericClass<String>{
@Override
public Class<String> getMyType(){
return String.class;
}
}
如果你有这样一个类:
public class GenericClass<T> {
private T data;
}
T变量,那么你可以打印T名称:
System.out.println(data.getClass().getSimpleName()); // "String", "Integer", etc.
这是我的解决方案
public class GenericClass<T>
{
private Class<T> realType;
public GenericClass() {
findTypeArguments(getClass());
}
private void findTypeArguments(Type t) {
if (t instanceof ParameterizedType) {
Type[] typeArgs = ((ParameterizedType) t).getActualTypeArguments();
realType = (Class<T>) typeArgs[0];
} else {
Class c = (Class) t;
findTypeArguments(c.getGenericSuperclass());
}
}
public Type getMyType()
{
// How do I return the type of T? (your question)
return realType;
}
}
不管你的类层次结构有多少层, 这个解决方案仍然有效,例如:
public class FirstLevelChild<T> extends GenericClass<T> {
}
public class SecondLevelChild extends FirstLevelChild<String> {
}
在本例中,getMyType() = java.lang.String