I just started learning Java and am having difficulty with understanding classes. One of my most recent assignments was to create a class called Triangle that would - given user input from the main method - take in the input to test if the hypothetical "triangle" is equilateral, isosceles, or scalene and then return that to main. I was able to get the program to work.

However, I did not follow the assignment's implementation guidelines, which specified having two additional methods that calculated largest and smallest side-length. I am wondering, after the fact, if anyone can look at what I did and let me know if they can see and or explain - in beginner terms - why having those two methods would be needed if it works without them (i.e. is my program somehow at a disadvantage by nature of NOT having them) and if so, what was I doing wrong that kept throwing errors when I tried to implement those methods?

I'll include both the assignment guidelines (for reference since I do not assume anyone is a mind reader) and then my code:

The assignment guidelines:

Your assignment is to write a class definition (not a program, there is no main method) named Triangle (saved in a file Triangle.java). Triangle has 3 instance variables: int side1, side2, side3; The class Triangle must include the following constructors and methods: (If your class does not contain any of the following methods, points will be deducted).

public Triangle (int s1, int s2, int s3) 

• Sets up a triangle with the specified side lengths.

private int largest() 

• Returns the length of the longest side of the triangle. This is a helper method.

private int shortest() 

• Returns the length of the shortest side of the triangle. This is a helper method.

public boolean is_equilateral() 

• Determines whether a triangle is equilateral. If the longest side is equal to the shortest side, then the triangle is equilateral.

public boolean is_isosceles() 

• Determines whether a triangle is isosceles. Any (and at least) two sides must be equal.

public boolean is_scalene() 

• Determines whether a triangle is scalene. No two sides are equal.

public String toString() 

• Prints the sides of the triangle.

My code:

public class Triangle {

private int side1, side2, side3;   // 3 sides for user-input of triangle side length    

public Triangle (int s1, int s2, int s3){  // instance variables
    
        side1 = s1;
    
        side2 = s2;
    
        side3 = s3;
    
    
}

// My largest and shortest helper methods never got off the ground
// I left them in for kicks and giggles as comments

//      private int largest(int s1, int s2, int s3) {   <------ Why are these supposed to be declared as private?
//
//          int max = Math.max(Math.max(s1, s2), s3);                                                                   // and is_scalene to determine what type of     
//          return max;
//          }

//      private int shortest(int s1, int s2, int s3) { 
//        // all the other is_x methods below   
//          int min = Math.min(Math.min(s1, s2), s3);   
//          return min;
//          }
    
    
    public boolean is_equilateral() { // These methods will return a true or false back to main()
        
        int max = Math.max(Math.max(side1, side2),side3);  // Because I couldn't get largest/smallest
        int min = Math.min(Math.min(side1, side2), side3); // to work, I opted to use Java's Math.max/min
                                                           // methods instead.  
        boolean answer = false;     // default answer set to false                              
        
        if (max == min)     // if the largest # is also equal to the smallest # (i.e. all equal) 
                            // then true else false
        {
            answer = true;
        }
        
        else
        {
            answer = false;
        }

        return answer;
    }
    
    
    public boolean is_isosceles() {
        
        boolean answer = false; 
        
        if(side1 == side2 || side1 == side3 || side2 == side3)
        {
            answer = true;  // if any 2 sides are equal then true, else false
        }
        
        else
        {
            answer = false;
        }
        
        return answer;
        
    }
    
    public boolean is_scalene() {
        
        boolean answer = false;
        
        if(side1 != side2 && side2 != side3) 
        {
            answer = true;  // if all #'s are different, then true, else false
        }
        
        else 
        {
            answer = false;
        }
        
        return answer;
    }
    
    public String toString() {  // print results on same line
        
        return "" + this.side1 + " " + this.side2 + " " + this.side3 + "\n\n";
        
    }



}

// Then the test file that we use to ensure that the class is working is below

import java.util.Scanner;
public class Assignment4 
{

//===========================================================
// Create and determine properties of various triangles.
//===========================================================
public static void main (String[] args) 
{
  Scanner console = new Scanner(System.in);
  int num1, num2, num3;
  String another;
  
  // repeat until the user enter 'n'
  do
  {
     // get the input
     System.out.println("Enter the sides of the triangle: ");
     num1 = console.nextInt();
     num2 = console.nextInt();
     num3 = console.nextInt();
  

     // create the Triangle
     Triangle myTriangle = new Triangle (num1, num2, num3);

     // print the Triangle
     System.out.println(myTriangle.toString() + " triangle:");

     //check the isosceles
     if (myTriangle.is_isosceles())
       System.out.println("It is isosceles");
     else
       System.out.println("It is not isosceles");
    
     //check the equilateral
     if (myTriangle.is_equilateral())
       System.out.println("It is equilateral");
     else
       System.out.println("It is not a equilateral");
    
     //check the scalene
     if (myTriangle.is_scalene())
       System.out.println("It is scalene");
     else
       System.out.println("It is not scalene");

     // find if the user want to repeat
     System.out.println();
     System.out.print("Check another Triangle (y/n)? ");
     another = console.next();

  } while (another.equalsIgnoreCase("y"));


  }  // method main

}  // class Assignment4