ArrayList Contains with Object always returns false

Here is my code:

package bikeproject;
import java.util.ArrayList;
import java.util.Random;
public class BikerList {
public static void main(String[] args) {
ArrayList<Bike> bikes = new ArrayList<Bike>();
int mountainBikeSales = 0;
int roadBikeSales = 0;
fillArray(bikes);
displayStock(bikes);
//		calculateStock(bikes);
System.out.println(displayBkeNumbers(bikes));
}
static void fillArray(ArrayList<Bike> bikes) {
Random rand = new Random();
//		int number = 2;
//		int a = rand.nextInt(2);
for (int i = 0; i < 10; i++) {
if (rand.nextInt(2) < 1) {
//				System.out.println(rand.nextInt(2));
bikes.add(new MountainBike());
} else {
//				System.out.println(rand.nextInt(2));
bikes.add(new RoadBike());
}
}
}
static void displayStock(ArrayList<Bike> bikes) {
for (Bike bike : bikes) {
System.out.println(bike);
}
}
static int calculateStock(ArrayList<Bike> bikes) {
int bikesSold = 0;
for (Bike bike : bikes) {
if (bikes.contains(new MountainBike())) {
bikesSold++;
}
}
return bikesSold;
}
static String displayBkeNumbers(ArrayList<Bike> bikes) {
int mb = 0;
int rb = 0;
mb = calculateStock(bikes);
rb = bikes.size() - mb;
return "\nStock Levels" + "\nWe have " + mb + " mountain Bike in Stock" + "\nWe have " + rb
+ " Road bikes in Stock";
}
}

I really believe there is an error in the calculateStock() method because it always returns false, In the calculateStock() method I want to add the value to the bikesSold variable if each bike in the array is an instance of a mountain bike.

The output generated by the code above:

Stock Levels
We have 0 mountain Bike in Stock
We have 10 Road bikes in Stock

Mountain Bike is always 0 although it is already in the ArrayList.

The expected output, something like this:

Stock Levels
We have 4 Mountain Bikes in stock
We have 6 Road Bikes in stock

static int calculateStock(ArrayList<Bike> bikes) {
    int bikesSold = 0;
    for (Bike bike : bikes) {
        if (bikes.contains(new MountainBike())) { //problematic line
            bikesSold++;
        }
    }
    return bikesSold;
}

does not work, because, .contains(Object o):
> returns true if and only if this list contains at least one element e such that Objects.equals(o, e).

So, bikes.contains(new MountainBike()) will always return true as long as there is, at least, one instance of the MountainBike contained (according to the .equals(Object o) method) in the bikes list.

Rather, you should want to check if the current object is an instance of a particular type you would want to check it against (MountainBike, in this case), like this:

static int calculateStock(ArrayList<Bike> bikes) {
    int bikesSold = 0;
    for (Bike bike : bikes) {
        if (bike instanceof MountainBike) {
            bikesSold++;
        }
    }
    return bikesSold;
}

This if (bikes.contains(new MountainBike())) creates a new object and checks if it's already in the list. It's not.

You need to do something like if (bike instanceof Mountainbike) .

There are better ways, but that will solve your problem.