Classify a triangle given the length of its three sides as input.

TriangleDemo.java

package com.example;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashSet;
import java.util.List;
import java.util.Scanner;
import java.util.Set;

public class TriangleDemo {

    public static final int INVALID = -1;
    public static final int EQUILATER = 1;
    public static final int ISOSCELES = 2;
    public static final int SCALENE = 3;
    private static final List<Integer> TYPES = new ArrayList<Integer>(3);

    static {
        TYPES.add(EQUILATER);
        TYPES.add(ISOSCELES);
        TYPES.add(SCALENE);
    }

    public static int triangle(int a, int b, int c) {
        int[] sides = {a, b, c};
        Arrays.sort(sides);
        if (sides[0] + sides[1] <= sides[2]) {
            return INVALID;
        }
        Set<Integer> differentSides = new HashSet<Integer>();
        differentSides.addAll(Arrays.asList(a, b, c));
        return TYPES.get(differentSides.size() - 1);
    }
	
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        String line;
        do {
            System.out.println("Type three numbers separated by a space: ");
            line = input.nextLine().trim();
            if (line.isEmpty()) {
                break;
            }
            String[] sides = line.split("\\s+");
            int triangle = triangle(Integer.parseInt(sides[0]),
                                    Integer.parseInt(sides[1]),
                                    Integer.parseInt(sides[2]));
            String message = "The triangle is: ";
            switch (triangle) {
            case EQUILATER:
                message += "equilater";
                break;
            case ISOSCELES:
                message += "isosceles";
                break;
            case SCALENE:
                message += "scalene";
                break;
            default:
                message += "invalid";
            }
            System.out.println(message);
        } while (!line.isEmpty());
    }

}