我对JAVA泛型引出的思考

class Info<T extends Number>
{
private T var;
public T getVar()
{
return var;
}
public void setVar(T var)
{
this.var=var;
}
public String toString()
{
return this.var.toString();
}
}
public class Demo21
{
public static void main(String[] args)
{
Info<Integer> i= fun(30);
System.out.println(i.getVar());
}
public static <T extends Number> Info<T> fun (T param)//关于这段代码的声明
{
Info<T> temp=new Info<T>();
temp.setVar(param);
return temp;
}
}