Triangle

Runner.java

public class Runner {
    public static void main(String[] args) {
        Triangle triangle1 = new Triangle(10, 6, 5);
        Triangle triangle2 = new Triangle(20, 15, 10);
        System.out.println(triangle1.getArea());
        System.out.println(triangle2.getArea());
        Triangle triangle3 = new Triangle(20, 150, 10);
        System.out.println(triangle3.getSideA());
        Triangle triangle4 = new Triangle(20, 15, -10);
        System.out.println(triangle4.getSideB());

    }
}

Triangle.java

import java.util.IllegalFormatException;

public class Triangle {
    private double sideA;
    private double sideB;
    private double sideC;

    Triangle(double sideA, double sideB, double sideC) throws IllegalFormatException {
        if (sideA > 0 && sideB > 0 && sideC > 0) {
            if ((sideA + sideB) > sideC && (sideB + sideC) > sideA && (sideC + sideA) > sideB) {
                this.sideA = sideA;
                this.sideB = sideB;
                this.sideC = sideC;
            } else{
                System.out.println("Triangle with such sides can't exist");
                System.out.println("Create new triangle");
            }
        } else {
            System.out.println("Side can't be below zero");
            System.out.println("Create new triangle");
        }
    }

    public double getSideA() {
        return sideA;
    }

    public double getSideB() {
        return sideB;
    }

    public double getSideC() {
        return sideC;
    }

    public double getArea() {
        double p = (this.getSideA() + this.getSideB() + this.getSideC()) / 2;
        return Math.sqrt(p * (p - this.getSideA()) * (p - this.getSideB()) * (p - this.getSideC()));
    }
}