(Java) Calling methods in constructor?

Question

***I tried searching but I just can't understand what comes up. Sorry.

I am working on a server/client project for school. I am at my wit's end and I am about to give up. I do not have notes from class so I need some help. First I will post the directions I was given, then my current code, then my problem.

SERVER DIRECTIONS:

• The Triangle class must have the following instance variables: side_a, side_b, side_c. Create a static variable to keep track of the number of Triangle objects created. Also create a static variable to hold the total of the perimeters of all Triangle objects created.

• A three parameter constructor of the Triangle class should assign a trio of input values to the instance variables of the object. If not a valid triangle set all of the sides to 1. Create a separate private method called isValid(). The sum of any two sides of a triangle must be greater than the third in order to represent a valid triangle. No side may be 0 or negative. The constructor should also add 1 to the count and also call a method to calculate and then add the perimeter for that object to an accumulator.

• The Triangle class must have the following methods as stated above:

• public boolean is_right() public boolean is_isoc()
• public boolean is_equil() public boolean is_scal()

• public String toString() – returns the values for the 3 sides of the Triangle

• You should also add a method to the Triangle class called calc_perim. This method will use the sides of the Triangle object to calculate the perimeter for that object.

• addTotalPerim. This method will call calc_perim and add the perimeter for that object to an accumulator.
• reduceTotalPerim. This method should subtract the perimeter for that object from the accumulator.

SERVER CODE:

public class Triangle {
private int side_a, side_b, side_c;
private static int count;
**//PROBLEM 1: Java tells me 'perim' is not used.**
private static int perim; 
private boolean valid;




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

  side_a = s1; side_b = s2; side_c = s3;

  **//PROBLEM 2: Java tells me 'v' is not used.**

  boolean v = isValid();

  if (v = false)
  {side_a = 1; side_b = 1; side_c = 1;}



  Triangle.count++;
  calc_perim(s1,s2,s3);
  addTotalPerim();
  reduceTotalPerim();



  }

    private int calc_perim()    
   {
    int perimeterCalc = side_a + side_b + side_c;


    return perimeterCalc;
    }

   private void addTotalPerim()
   {


  Triangle.perim += calc_perim();

   }

   private void reduceTotalPerim()
   {
    Triangle.perim -= calc_perim();

  }

    private boolean isValid()
   {

    boolean valid1;    

   if  (side_a < 1)
       { valid1 = false;}
   else if (side_b < 1)
       { valid1 = false;}
   else if (side_c < 1)
       { valid1 = false;}
   else if ((side_a + side_b) < side_c || (side_a + side_b) == side_c)
       { valid1 = false;}
   else
       { valid1 = true;}

   return valid1;

   }

   public boolean is_right()
   {
   boolean right;
   if (((side_a * side_a) + (side_b * side_b)) == (side_c * side_c))
       right = true;
   else
       right = false;

   return right;
  }

  public boolean is_isoc()
  {
     boolean isoc;

   if (side_a == side_b)
       isoc = true;
   else if (side_a == side_c)
       isoc = true;
   else if (side_b == side_c)
       isoc = true;
   else
       isoc = false;

   return isoc;

  }

  public boolean is_equil()
  {
   boolean equil;

   if (side_a == side_b && side_a == side_c)
       equil = true;
   else
       equil = false;

   return equil;

   }

   public boolean is_scal()
  {
   boolean scal;

   if (side_a == side_b || side_a == side_c || side_b == side_c)
       scal = false;
   else 
       scal = true;

   return scal;
  }

   public String toString()

  {
  return "Side 1: " + side_a + " Side 2: " + side_b + " Side 3: " + side_c;

  }

  }

Sorry about formatting but this site has a terrible way of formatting code, unless I'm misunderstanding something...

SERVER PROBLEMS:

What is the correct way to add/subtract the perimeter obtained via method calc_perim to varible perim? The directions say to call the calc_perim method in the constructor but I can't figure out how, so I just made it do its calculations on its own.

In the constructor, after calling method isValid(), why am I told by Java that variable 'v' is not used? Did I call isValid() incorrectly? >>>>> How do I call a method in the constructor? <<<<<

Other than that major issue, the server class works fine.

Answer 1

The "is not used" message from the Java compiler is technically a warning, not an error, so you could run your program even with the message still in effect if you really wanted to. But your instincts are correct- it's a bad idea to ignore those messages.

In this case, your code has a serious problem. You're calling v = false , which means that you're assigning a value of false to v . Change it to v == false . By using == , you're doing a comparison, which is what you really want.

Answer 2

Suggestions:

1. Within Triangle class, initialize the static variables.

   private static int count = 0; private static int perim = 0;

2. Within Triangle constructor, change,

   if (v = false)

to

if (v == false)

3. Change calc_perim as:

   private void addTotalPerim() { perim += calc_perim(); } private void reduceTotalPerim() { perim -= calc_perim(); }

4. Why you call reduceTotalPerim() after addTotalPerim(), didn't get this clear.

5. isValid function should check all combinations like a+b>c, b+c>a, c+a>b, if any one fails should be invalid