New to java stuck on Decision Making in java

Question

I have created a class named Bicycle now I want to limit the gear of my bicycle to 6. A value greater than 6 will give an error and message will be displayed:

System.out.println "Error...!! Please enter a number between 1-6".

Can someone tell me what needs to be done to get the desired result in the below mentioned program? And for Decision Making in java where do I need to declare the condition so it gets executed?

public class Bicycle {
   
        int cadence = 0;
        int speed = 0;
        int gear = 1;

    void changeCadence(int newValue) {
        cadence = newValue;
    }

    void changeGear(int newValue) {
        gear = newValue;
    }

    void speedUp(int increment) { speed = speed + increment; }

    void applyBrakes(int decrement) { speed = speed - decrement;}

    void printStates() {
        System.out.println("cadence:" + cadence + " speed:" + speed + " gear:" + gear);
    }

    void vehicleType() {
        System.out.println("Vehicle Type: Bicycle");
    }
}
   class BicycleDemo {

       public static void main(String[] args) {

                Bicycle bike1 = new Bicycle();
                Bicycle bike2 = new Bicycle();

                bike1.changeCadence(50);
                bike1.applyBrakes(0);
                bike1.changeGear(1);
                bike1.printStates();

                bike2.changeCadence(50);
                bike2.speedUp(10);
                bike2.changeGear(2);
                bike2.changeCadence(40);
                bike2.speedUp(20);
                bike2.changeGear(4);
                bike2.printStates();
            } 
        }

Answer 1

Change

void changeGear(int newValue) {
    gear = newValue;
}

To

void changeGear(int newValue) {
    if (newValue < 1 || newValue > 6) {
        System.out.println("Error...!! Please enter a number between 1-6");
    } else {
    gear = newValue;
    }
}