Ian Robertson在这篇文章中描述的技巧对我很有用。

简单粗暴的例子:

 public abstract class AbstractDAO<T extends EntityInterface, U extends QueryCriteria, V>
 {
    /**
     * Method returns class implementing EntityInterface which was used in class
     * extending AbstractDAO
     *
     * @return Class<T extends EntityInterface>
     */
    public Class<T> returnedClass()
    {
        return (Class<T>) getTypeArguments(AbstractDAO.class, getClass()).get(0);
    }

    /**
     * Get the underlying class for a type, or null if the type is a variable
     * type.
     *
     * @param type the type
     * @return the underlying class
     */
    public static Class<?> getClass(Type type)
    {
        if (type instanceof Class) {
            return (Class) type;
        } else if (type instanceof ParameterizedType) {
            return getClass(((ParameterizedType) type).getRawType());
        } else if (type instanceof GenericArrayType) {
            Type componentType = ((GenericArrayType) type).getGenericComponentType();
            Class<?> componentClass = getClass(componentType);
            if (componentClass != null) {
                return Array.newInstance(componentClass, 0).getClass();
            } else {
                return null;
            }
        } else {
            return null;
        }
    }

    /**
     * Get the actual type arguments a child class has used to extend a generic
     * base class.
     *
     * @param baseClass the base class
     * @param childClass the child class
     * @return a list of the raw classes for the actual type arguments.
     */
    public static <T> List<Class<?>> getTypeArguments(
            Class<T> baseClass, Class<? extends T> childClass)
    {
        Map<Type, Type> resolvedTypes = new HashMap<Type, Type>();
        Type type = childClass;
        // start walking up the inheritance hierarchy until we hit baseClass
        while (!getClass(type).equals(baseClass)) {
            if (type instanceof Class) {
                // there is no useful information for us in raw types, so just keep going.
                type = ((Class) type).getGenericSuperclass();
            } else {
                ParameterizedType parameterizedType = (ParameterizedType) type;
                Class<?> rawType = (Class) parameterizedType.getRawType();

                Type[] actualTypeArguments = parameterizedType.getActualTypeArguments();
                TypeVariable<?>[] typeParameters = rawType.getTypeParameters();
                for (int i = 0; i < actualTypeArguments.length; i++) {
                    resolvedTypes.put(typeParameters[i], actualTypeArguments[i]);
                }

                if (!rawType.equals(baseClass)) {
                    type = rawType.getGenericSuperclass();
                }
            }
        }

        // finally, for each actual type argument provided to baseClass, determine (if possible)
        // the raw class for that type argument.
        Type[] actualTypeArguments;
        if (type instanceof Class) {
            actualTypeArguments = ((Class) type).getTypeParameters();
        } else {
            actualTypeArguments = ((ParameterizedType) type).getActualTypeArguments();
        }
        List<Class<?>> typeArgumentsAsClasses = new ArrayList<Class<?>>();
        // resolve types by chasing down type variables.
        for (Type baseType : actualTypeArguments) {
            while (resolvedTypes.containsKey(baseType)) {
                baseType = resolvedTypes.get(baseType);
            }
            typeArgumentsAsClasses.add(getClass(baseType));
        }
        return typeArgumentsAsClasses;
    }
  }

泛型在运行时不会具体化。这意味着信息在运行时不存在。

在向Java中添加泛型的同时保持向后兼容性是一项壮举(您可以看到关于它的开创性论文:让未来对过去更加安全:向Java编程语言添加泛型)。

关于这个问题有丰富的文献，有些人对目前的状态不满意，有些人说实际上这是一个诱惑，没有真正的需要。你可以阅读这两个链接，我发现它们很有趣。

如果你使用泛型类型存储变量，你可以很容易地解决这个问题，添加getClassType方法，如下所示:

public class Constant<T> {
  private T value;

  @SuppressWarnings("unchecked")
  public Class<T> getClassType () {
    return ((Class<T>) value.getClass());
  }
}

我稍后使用提供的类对象来检查它是否是给定类的实例，如下所示:

Constant<?> constant = ...;
if (constant.getClassType().equals(Integer.class)) {
    Constant<Integer> integerConstant = (Constant<Integer>)constant;
    Integer value = integerConstant.getValue();
    // ...
}

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.

一个简单的解决方案，这种出租车如下

public class GenericDemo<T>{
    private T type;

    GenericDemo(T t)
    {
        this.type = t;
    }

    public String getType()
    {
        return this.type.getClass().getName();
    }

    public static void main(String[] args)
    {
        GenericDemo<Integer> obj = new  GenericDemo<Integer>(5);
        System.out.println("Type: "+ obj.getType());
    }
}

这是我的解决方案:

import java.lang.reflect.Type;
import java.lang.reflect.TypeVariable;

public class GenericClass<T extends String> {

  public static void main(String[] args) {
     for (TypeVariable typeParam : GenericClass.class.getTypeParameters()) {
      System.out.println(typeParam.getName());
      for (Type bound : typeParam.getBounds()) {
         System.out.println(bound);
      }
    }
  }
}