我不知道编译器的提示干什么用的

#include<iostream>
using namespace std;
class tricycle
{
public:
    int getspeed();
    void setspeed();
    void pedal();
    void brake();
private:
    int speed;
};
int tricycle::getspeed() {
    return speed;
}
void tricycle::setspeed(int newspeed)
{   if (newspeed>=0)
    {
        speed=newspeed;
    }
}
void tricycle::pedal()
{   setspeed(speed+1);
    cout << "\npedaling;tricyclespeed" <<speed<< endl;
}
void tricycle::brake()
{
setspeed(speed-1);
    cout << "speed" <<speed<< endl;}
int main()
{
    tricycle zxc;
    zxc.setspeed(0);
    zxc.pedal();
    zxc.pedal();
    zxc.brake();
    zxc.brake();
    zxc.brake();
    return 0;
}这代码哪有问题?