Question

java泛型的问题

class Gen<T>
{
private T o;
public Gen(T a)
{this.o=a;}
public void showTypeName()
{
System.out.println("类型是："+o.getClass().getName());
}
}
Dog dog1=new Dog();
Dog dog2=new Dog();
Gen<Dog> gen1=new Gen<Dog>(dog1);
Gen gen2=new Gen(dog2);
gen1.showTypeName();
gen2.showTypeName();

两个都能输出数据类型，有什么区别？
Gen<Dog> gen1=new Gen<Dog>(dog1);
Gen gen2=new Gen(dog2);

这两有什么区别，第二个简单，为什么大家都用第一个。而且第二个系统会提示：
Multiple markers at this line
- Gen is a raw type. References to generic type Gen<T> should be
parameterized
- Type safety: The constructor Gen(Object) belongs to the raw type Gen.
References to generic type Gen<T> should be parameterized
- Line breakpoint:Demo2 [line: 21] - main(String[])
- Gen is a raw type. References to generic type Gen<T> should be
parameterized

Answer 1

泛型确保了数据类型的唯一性，减少了因为数据类型出现的错误

Answer 2

一样的