如果要扩展或实现任何使用泛型的类/接口，则可以获得父类/接口的泛型类型，而不必修改任何现有类/接口。

可能有三种可能性，

案例1当您的类正在扩展使用泛型的类时

public class TestGenerics {
    public static void main(String[] args) {
        Type type = TestMySuperGenericType.class.getGenericSuperclass();
        Type[] gTypes = ((ParameterizedType)type).getActualTypeArguments();
        for(Type gType : gTypes){
            System.out.println("Generic type:"+gType.toString());
        }
    }
}

class GenericClass<T> {
    public void print(T obj){};
}

class TestMySuperGenericType extends GenericClass<Integer> {
}

案例2当类实现使用泛型的接口时

public class TestGenerics {
    public static void main(String[] args) {
        Type[] interfaces = TestMySuperGenericType.class.getGenericInterfaces();
        for(Type type : interfaces){
            Type[] gTypes = ((ParameterizedType)type).getActualTypeArguments();
            for(Type gType : gTypes){
                System.out.println("Generic type:"+gType.toString());
            }
        }
    }
}

interface GenericClass<T> {
    public void print(T obj);
}

class TestMySuperGenericType implements GenericClass<Integer> {
    public void print(Integer obj){}
}

案例3当您的接口扩展使用Generics的接口时

public class TestGenerics {
    public static void main(String[] args) {
        Type[] interfaces = TestMySuperGenericType.class.getGenericInterfaces();
        for(Type type : interfaces){
            Type[] gTypes = ((ParameterizedType)type).getActualTypeArguments();
            for(Type gType : gTypes){
                System.out.println("Generic type:"+gType.toString());
            }
        }
    }
}

interface GenericClass<T> {
    public void print(T obj);
}

interface TestMySuperGenericType extends GenericClass<Integer> {
}

然而，有一个小漏洞：如果您将Foo类定义为抽象类。这意味着您必须将类实例化为：

Foo<MyType> myFoo = new Foo<MyType>(){};

（注意末端的双撑杆。）

现在，您可以在运行时检索T的类型：

Type mySuperclass = myFoo.getClass().getGenericSuperclass();
Type tType = ((ParameterizedType)mySuperclass).getActualTypeArguments()[0];

然而，请注意，mySuperclass必须是实际定义T的最终类型的类定义的超类。

它也不是很优雅，但你必须决定你喜欢新的Foo＜MyType＞（）｛｝还是新的Foo＜MyType＜（MyType.class）；在您的代码中。

例如：

import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;

import java.util.ArrayDeque;
import java.util.Deque;
import java.util.NoSuchElementException;

/**
 * Captures and silently ignores stack exceptions upon popping.
 */
public abstract class SilentStack<E> extends ArrayDeque<E> {
  public E pop() {
    try {
      return super.pop();
    }
    catch( NoSuchElementException nsee ) {
      return create();
    }
  }

  public E create() {
    try {
      Type sooper = getClass().getGenericSuperclass();
      Type t = ((ParameterizedType)sooper).getActualTypeArguments()[ 0 ];

      return (E)(Class.forName( t.toString() ).newInstance());
    }
    catch( Exception e ) {
      return null;
    }
  }
}

然后：

public class Main {
    // Note the braces...
    private Deque<String> stack = new SilentStack<String>(){};

    public static void main( String args[] ) {
      // Returns a new instance of String.
      String s = stack.pop();
      System.out.printf( "s = '%s'\n", s );
    }
}

你不能这样做，因为类型删除。另请参阅堆栈溢出问题Java泛型-类型擦除-何时发生以及发生什么。

这很直接。如果您需要来自同一类：

Class clazz = this.getClass();
ParameterizedType parameterizedType = (ParameterizedType) clazz.getGenericSuperclass();
try {
        Class typeClass = Class.forName( parameterizedType.getActualTypeArguments()[0].getTypeName() );
        // You have the instance of type 'T' in typeClass variable

        System.out.println( "Class instance name: "+  typeClass.getName() );
    } catch (ClassNotFoundException e) {
        System.out.println( "ClassNotFound!! Something wrong! "+ e.getMessage() );
    }

实际上，这是可能的（没有外部库！）

以下是我对这个问题的（丑陋但有效的）解决方案：

import java.lang.reflect.TypeVariable;


public static <T> Class<T> getGenericClass() {
    __<T> instance = new __<T>();
    TypeVariable<?>[] parameters = instance.getClass().getTypeParameters(); 

    return (Class<T>)parameters[0].getClass();
}

// Generic helper class which (only) provides type information. This avoids the
//   usage of a local variable of type T, which would have to be initialized.
private final class __<T> {
    private __() { }
}

我根据这个问题中两个最有希望的解决方案之一创建了一个示例。

然而，至少在我的用例中，结果并不那么有希望。

只有一种方法有效，但您需要一个包含方法的超级类，泛型必须在子类中设置，并且不能动态分配（我的用例很遗憾）

import org.junit.jupiter.api.Test;

import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertThrows;


public class GenericTest {

    /**
     * only this will work!
     */
    @Test
    void testGetGenericTypeClassFromChildClassWithSpecifiedType() {
        TestClassWithSpecifiedType parent = new TestClassWithSpecifiedType();
        assertEquals(SomeGenericType.class, parent.getGenericTypeClass());
    }

    /**
     * won't work!
     */
    @Test
    void testGetGenericTypeClassFromChildClassWithUnspecifiedType() {
        TestClassWithUnspecifiedType<SomeGenericType> parent = new TestClassWithUnspecifiedType<>();
        assertThrows(IllegalStateException.class, parent::getGenericTypeClass);
    }

    /**
     * won't work
     */
    @Test
    void testGetGenericTypeClassWithUnspecifiedType() {
        SomeGenericTypedClass<SomeGenericType> parent = new SomeGenericTypedClass<>();
        assertThrows(IllegalStateException.class, parent::getGenericTypeClass);
    }

    /**
     * won't work
     * returns object instead!
     */
    @Test
    void testGetLoadedClassFromObject() {
        Foo<SomeGenericType> foo = new Foo<>();
        Class<?> barClass = foo.getBarClass();
        assertEquals(SomeGenericType.class, barClass);
    }

    /**
     * A class that has specified the type parameter
     */
    public static class TestClassWithSpecifiedType extends AbstractGenericTypedClass<SomeGenericType> {

    }

    /**
     * A class where the type parameter will be specified on demand
     *
     * @param <T>
     */
    public static class TestClassWithUnspecifiedType<T> extends AbstractGenericTypedClass<T> {

    }

    /**
     * An abstract class, because otherwise finding the parameter will not work
     */
    @SuppressWarnings("unchecked")
    public static abstract class AbstractGenericTypedClass<T> {
        @SuppressWarnings("unchecked")
        public Class<T> getGenericTypeClass() {
            try {
                String className = ((ParameterizedType) getClass().getGenericSuperclass()).getActualTypeArguments()[0].getTypeName();
                Class<?> clazz = Class.forName(className);
                return (Class<T>) clazz;
            } catch (Exception e) {
                throw new IllegalStateException("Class is not parametrized with generic type!!! Please use extends <> ");
            }
        }
    }

    /**
     * A typed class without abstract super class
     *
     * @param <T>
     */
    public static class SomeGenericTypedClass<T> {
        @SuppressWarnings("unchecked")
        public Class<T> getGenericTypeClass() {
            try {
                String className = ((ParameterizedType) getClass().getGenericSuperclass()).getActualTypeArguments()[0].getTypeName();
                Class<?> clazz = Class.forName(className);
                return (Class<T>) clazz;
            } catch (Exception e) {
                throw new IllegalStateException("Class is not parametrized with generic type!!! Please use extends <> ");
            }
        }
    }


    /**
     * Some generic type - won't work with primitives such as String, Integer, Double!
     */
    public static class SomeGenericType {

    }

    public static class Foo<T> {
        // The class:
        private final Class<?> barClass;

        public Foo() {
            try {
                // Im giving it [0] cuz Bar is the first TypeParam
                Type[] bounds = getClass().getTypeParameters()[0].getBounds();
                // Here, we get the class now:
                barClass = Class.forName(bounds[0].getTypeName());
            } catch (ClassNotFoundException e) {
                // will never happen!
                throw new Error("Something impossible happened!", e);
            }
        }

        public Class<?> getBarClass() {
            return barClass;
        }
    }
}

我真的不明白为什么这必须如此复杂，但我敢打赌，动态设置参数必须有一些技术限制。