"Triangle 1 is abstract; Cannot be instantiated" Driver error

Question

Coming across problems with not being able to to be instantiated even extending and trying to override it does nothing to fix it. Trying with a driver file and 2 other files to print results back. Been stuck for awhile, anything is appreciated at this point.

public abstract class Triangle extends Lot implements Comparable< TestTriangle> {

public abstract double calculateArea();

public abstract String getID();

public int compareTo(LotType1 o) {
    if (calculateArea() > o.calculateArea()) {
        return 1;
    } else if (calculateArea() < o.calculateArea()) {
        return -1;
    } else {
        return 0;
    }
}

@Override 
public String toString() {
    return "Lot ID: " + getID()
            + " Area: " + calculateArea();
}

}

Driver File =====

public class TestLots {

public static void main(String args[]){

Lot[] lots = {new Triangle1("L1",350, 200) {},
              new Triangle2("L2",100,270),
              new Triangle1("L3",100, 270),
              new Triangle2("L4",350,200)
             };


java.util.Arrays.sort(lots);

// print out sorted results
for (Lot lot: lots) {
  System.out.print(lot + " "); 
  System.out.println();
}

Hey! `Triangle` is abstract and therefore you cannot instantiate it. You need to implement `getID` and `calculateArea`. In case you've done that with `Triangle1` and `Triangle2`; please post those classes as well. — akuzminykh, Jun 21 '20 at 20:30
First, you dont have any class called Triangle1 or TriangleX, and Triangle is an abstract class, why? i preffer to you to remove the abstract and implement all the methods, like calculateArea and getID — Timor, Jun 21 '20 at 20:30

score 0 · Answer 1 · answered Jun 21 '20 at 20:38

An abstract class cannot be initiated. For you needs, first remove the abstract keyword from the class implementation. Then, Create an constructor which get your 3 parameters, implement the 2 methods, calculateArea and getID. Please try to start with this following code

import java.util.Comparator;

public class Triangle implements Comparator<Triangle> {
    private String id;

    public Triangle(String id) {
        this.id = id;
    }


    public double calculateArea() {
        int area = 0;
        //calculate your area
        return area;
    }

    public String getID() {
        return id;

    }

    @Override
    public String toString() {
        return "Triangle ID: " + getID()
                + " Area: " + calculateArea();
    }

    @Override
    public int compare(Triangle t1, Triangle t2) {
        if (t1.calculateArea() > t2.calculateArea()) {
            return 1;
        } else if (t1.calculateArea() < t2.calculateArea()) {
            return -1;
        } else {
            return 0;
        }
    }
}

score 0 · Answer 2 · answered Jun 22 '20 at 01:46

Java does not allow instantiation of abstract class directly for itself.

Can we instantiate an abstract class?

Create an abstract class called Shape -> it contains an abstract method calculateArea.

Then triangle can extend this class to become an concrete implementation. Then you can instantiate objects from it.

"Triangle 1 is abstract; Cannot be instantiated" Driver error

2 Answers2