Ifs com Helder

main.java

import java.util.Scanner;

public class condici {

    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        double l1, l2, l3;

        System.out.println("É triângulo?");

        System.out.println("Lado 1:");
        l1 = input.nextDouble();

        System.out.println("Lado 2:");
        l2 = input.nextDouble();

        System.out.println("Lado 3:");
        l3 = input.nextDouble();

        if (this.isTriangle(this.l1, this.l2, this.l3)) {
            System.out.println("É um triângulo");
            if (this.isTriangleEquilatero(this.l1, this.l2, this.l3)) {
                System.out.println("O triângulo é equilátero");
            } else if (this.isTriangleIsoceles(this.l1, this.l2, this.l3)) {
                System.out.println("O triângulo é isóceles");
            } else if (this.isTriangleEscaleno(this.l1, this.l2, this.l3) {
                System.out.println("O triângulo é escaleno");
            }
        } else {
            System.out.println("Não é triângulo");
        }

        input.close();

    }

    public boolean isTriangle(double l1, double l2, double l3) {
        return (l1 + l2 > l3) && (l2 + l3 > l1) && (l1 + l3 > l2);
    }
    public boolean isTriangleEquilatero(double l1, double l2, double l3) {
        return l1 == l2 && l2 == l3;
    }

    public boolean isTriangleIsoceles(double l1, double l2, double l3) {
        return (l1 == l2 && l2 != l3) || (l1 != l2 && l1 == l3) || (l2 == l3 && l3 != l1);
    }
    
    public boolean isTriangleEscaleno(double l1, double l2, double l3) {
        return l1 != l2 && l2 != l3;
    }

}