Triangle Problem

[Menios Menelaos]

Hey guys.

I hope someone can help me on this very irritating problem i cant seem to solve. Heres the brief of what i have to do:

Design and implement a program that accepts three integer values from the user and then evaluates them to see if they would correspond to an equilateral, isosceles, or scalene triangle. (An equilateral triangle has three sides of equal length, an isosceles triangle has two sides of equal length, and a scalene triangle has no sides of equal length.) The result of the evaluation is then revealed to the user.

*Note -
you got to make use of the javax.swing class JOptionPane for all user interaction.

two classes (in two files): the first being a “MyApplication” class that contains a main() method which instantiates an instance of a Triangle; and a second, separate class “Triangle”, that encapsulates the methods and data of a Triangle.

Ok so basically from this, i have come up with this:

*
* MyApplication.java
*/
import javax.swing.JOptionPane;
 
public class MyApplication {
 
/** Creates a new instance of myApplication */
public MyApplication() {
}
/**
* @param args the command line arguments
*/
 

public static void main(String[] args, Object outcome)
{
String message = "The Triangle Problem";
JOptionPane.showMessageDialog( null, message );
 
// obtain three integer values representing side lengths
int[ ] intArray = new int[ 3 ];
for( int i = 0; i < intArray.length; i++ )
{
message = "Enter an integer value for triangle side "
+ ( i + 1 ) + ":";
 
        // gather integer value representing side here…
        //String input = JOptionPane.showInputDialog(null, message );
        //intArray[i] = Integer.parseInt(input);
}
        // construct and evaluate the triangle
        //Triangle triangle = new Triangle(intArray[0], intArray[1], intArray[2]);
        //String outcome = triangle.evaluate( );
 
        //intArray[0] = Side1
        //intArray[1] = Side2 
        //intArray[2] = Side3
        //New Triangle = triangle1(intArray)
        //Triangle.evaluate()
 
// present the outcome to the user
JOptionPane.showMessageDialog( null, outcome );
}
}
//------- end of file -------------------------------------/    

&

  /**
* Triangle.java
*/
import javax.swing.JOptionPane;
public class Triangle
{
   private static int Side1, Side2, Side3;

    public Triangle() {}
    
        private static void acceptThreeIntegers( )
    {
    String strSide1 = JOptionPane.showInputDialog( "Enter side 1: ");
        Side1 = Integer.parseInt( strSide1 );
        
    String strSide2 = JOptionPane.showInputDialog( "Enter Side 2: ");
        Side2 = Integer.parseInt( strSide2 );
        
    String strSide3 = JOptionPane.showInputDialog( "Enter Side 3: ");
        Side3 = Integer.parseInt( strSide3 );
    }
        
        private static void useMethod( )
    {
    if( checkForNegatives( ) == false )
    {
    if (checkForTriangle() == true)
    {    
       String result = evaluate( );
       JOptionPane.showMessageDialog( null, result );
    }
    else
       JOptionPane.showMessageDialog( null, "Impossible", "Results", JOptionPane.PLAIN_MESSAGE );   
    }
   else
       JOptionPane.showMessageDialog( null, "Impossible", "Results", JOptionPane.PLAIN_MESSAGE  );   
    
   }
   private static boolean checkForNegatives( )
    {
    if (Side1 <=0 || Side2 <=0 || Side3 <=0)
       return true;
    else return false; 
    }
    
/** evaluate if a triangle is physically possible*/
    private static boolean checkForTriangle( )
    {
    if (Side1 + Side2 - Side3 <=0 ||
        Side1 + Side3 - Side2 <=0 ||
        Side2 + Side3 - Side1 <=0)
    return false;
    else return true;
    }
 
 
    private static String evaluate( )
    {
    if (Side1 == Side2 && Side2 == Side3)
    {
    return "Equilateral";
    }
    if (Side1 == Side2 && Side2 != Side3 ||
        Side1 == Side3 && Side2 != Side3 ||
        Side2 == Side3 && Side1 != Side2)
    {
    return "Isosceles ";
    }
    if (Side1 != Side2 && Side2 != Side3 ||
        Side1 != Side2 && Side1 != Side3)
    {
    return "Scalene";
    }
    return "test value";
    }
    
    public static void main (String[] args)
    {
    acceptThreeIntegers( );
    useMethod( );
    }
    
    //public static void Triangle(intArray) {
        //Side1 = intArray[0]
        //Side2 = intArray[1]
        //Side3 = intArray[2]
    //}
 
}  

My problem is im confused on what parts i need to cut over to the myapplication file and the triangle file. I know this may seem basic stuff, but im not used to doing this in java.

Also, im not 100% sure on setting the values into an array and then passing it to the triangle class. As you can see from the lines ive commented out, i tried something like this:
intArray[0] = side1 intArray[1] = side2 etc...then call the triangle using New Triangle = triangle1(intArray) then Triangle.evaluate().
but this didnt work.

So yes, please can someone help me out, ive been trying and trying and i really wanna get this to work.

Many thanks
Menios

[fred rosenberger]

looking at your code for about 2 seconds, two things popped out:

public static void Triangle(intArray) {
   Side1 = intArray[0]
   Side2 = intArray[1]
   Side3 = intArray[2]
}

1) you need semicolons at the end of each line

public static void Triangle(intArray) {
   Side1 = intArray[0][B];[/B]
   Side2 = intArray[1][B];[/B]
   Side3 = intArray[2][B];[/B]
}

2) in your method declaration, you need to tell it what intArray IS:

public static void Triangle([B]int [] [/B]intArray) {
   Side1 = intArray[0]
   Side2 = intArray[1]
   Side3 = intArray[2]
}

[Campbell Ritchie]

Welcome to JavaRanch

I wouldn't have told you to use the old-fashioned JOptionPane data entry rather than the more recent Scanner? Pass System.in to the Scanner constructor then you get methods which read input directly into primitives. They are usually called nextSomething. You can the print: "Enter the three sides" and enter 3 4 5 and when you push enter all three values are set up.
You need to watch Scanner; you may need to call nextLine() and discard the line every now and again otherwise it gets ahead of you, but I don't think you will have that problem in your little application.

I would have preferred to call the class with the main method in TriangleDemo or similar. But you are stuck with that name.

Set up a Triangle class with non-static fields for the three sides. Don't use an empty constructor. Set up the three sides in the constructor. You can do this simply by putting the 3 JOptionPane.showInputDialog calls in the constructor.
You will probably need to pass null as the first parameter to the input dialog, before "Enter side 1:".
If you pass negative lengths or values like 1 2 4 which won't make a triangle, throw an Exception from the constructor. If you don't know how to throw an Exception, show a JOptionPane with an error message and set the triangle to a default size) eg 3, 4, 5. Using private methods to test the lengths as you have done is a good idea; if those private methods access the fields, then they mustn't be "static."

Now you have reached the Triangle class with its class invariant intact (ie 3 sides with "real" lengths).

Never, never write == false or == true. You can get all sorts of serious errors if you write = instead of == by mistake.

Now you can set up a method which tests the type of triangle, and either returns it or displays it on a JOptionPane. You have got most of the logic in the evaluate() method, but you can make it much simpler with else if and else. Don't call the evaluate method static. Once you have tested that all three sides are equal, an else if makes it easier to test whether two sides are equal, then an else will assume all three sides are different lengths.
If you change your evaluate method to public void displayType(), you can then reduce your main method to a single line:

new Triangle().displayType();

You can make your boolean methods much simpler by looking at the Java Style Guidelines �10.5.2. Most of the members of the Triangle class which you have called static ought not to be static.

Hope I haven't confused you too much and good luck with it.

[Menios Menelaos]

Thanks for all the corrections up to now. I have to use the javax.swing class JOptionPane for all user interaction. After fixing the code a bit Triangle.java does what its suppossed to do but since i uncommented the rest of the code in MyApplication i get all type of errors. Any clues about what i m doing wrong?

     Triangle triangle = new [I]Triangle[/I](intArray[0], intArray[1], intArray[2]);
        [I]String outcome = triangle.evaluate( );[/I]
 
        intArray[0] = [I]Side1[/I] ;
        intArray[1] = [I]Side2[/I] ;
        intArray[2] = [I]Side3[/I] ;
        New Triangle = triangle1(intArray);
        Triangle.[I]evaluate[/I]() ;   

*all italics are shown as errors in Netbeans
Here is the Compile errors also

 init:
deps-jar:
Compiling 1 source file to C:\Users\Tier\Documents\NetBeansProjects\Triangle_Project\build\classes
C:\Users\Tier\Documents\NetBeansProjects\Triangle_Project\src\MyApplication.java:33: cannot find symbol
symbol  : constructor Triangle(int,int,int)
location: class Triangle
        Triangle triangle = new Triangle(intArray[0], intArray[1], intArray[2]);
C:\Users\Tier\Documents\NetBeansProjects\Triangle_Project\src\MyApplication.java:34: outcome is already defined in main(java.lang.String[],java.lang.Object)
        String outcome = triangle.evaluate( );
C:\Users\Tier\Documents\NetBeansProjects\Triangle_Project\src\MyApplication.java:34: evaluate() has private access in Triangle
        String outcome = triangle.evaluate( );
C:\Users\Tier\Documents\NetBeansProjects\Triangle_Project\src\MyApplication.java:36: cannot find symbol
symbol  : variable Side1
location: class MyApplication
        intArray[0] = Side1 ;
C:\Users\Tier\Documents\NetBeansProjects\Triangle_Project\src\MyApplication.java:37: cannot find symbol
symbol  : variable Side2
location: class MyApplication
        intArray[1] = Side2 ;
C:\Users\Tier\Documents\NetBeansProjects\Triangle_Project\src\MyApplication.java:38: cannot find symbol
symbol  : variable Side3
location: class MyApplication
        intArray[2] = Side3 ;
C:\Users\Tier\Documents\NetBeansProjects\Triangle_Project\src\MyApplication.java:39: cannot find symbol
symbol  : class New
location: class MyApplication
        New Triangle = triangle1(intArray);
C:\Users\Tier\Documents\NetBeansProjects\Triangle_Project\src\MyApplication.java:39: cannot find symbol
symbol  : method triangle1(int[])
location: class MyApplication
        New Triangle = triangle1(intArray);
8 errors
BUILD FAILED (total time: 0 seconds)   

[Menios Menelaos]

After some editing i m facing this error. What i m doing wrong here?
Thanks in advance

  init:
deps-jar:
Compiling 2 source files to C:\Users\Tier\Documents\NetBeansProjects\Triangle_Project\build\classes
C:\Users\Tier\Documents\NetBeansProjects\Triangle_Project\src\MyApplication.java:38: '(' or '[' expected
        new Triangle = triangle1(intArray);
1 error
BUILD FAILED (total time: 0 seconds)
  

   /**
* MyApplication.java
**/
import javax.swing.JOptionPane;
public class MyApplication {
 
/** Creates a new instance of myApplication */
public MyApplication() {
}
/**
* @param args the command line arguments
*/
 

public static void main(String[] args, Object outcome)
{
String message = "The Triangle Problem";
JOptionPane.showMessageDialog( null, message );
 
// obtain three integer values representing side lengths
int[ ] intArray = new int[ 3 ];
for( int i = 0; i < intArray.length; i++ )
{
message = "Enter an integer value for triangle side "
+ ( i + 1 ) + ":";
 
        // gather integer value representing side here…
        String input = JOptionPane.showInputDialog(null, message );
        intArray[i] = Integer.parseInt(input);
}
        // construct and evaluate the triangle
       Triangle triangle = new Triangle(intArray[0], intArray[1], intArray[2]);
       String outcome = triangle.evaluate( );
 
        intArray[0] = Side1 ;
        intArray[1] = Side2 ;
        intArray[2] = Side3 ;
        new Triangle = triangle1(intArray);
        Triangle.evaluate() ;
 
// present the outcome to the user
JOptionPane.showMessageDialog( null, outcome );
}
}
//------- end of file -------------------------------------/ 

[fred rosenberger]

I just may not be seeing it, but I don't see a constructor for a triangle that takes three ints, as you are calling here:

Triangle triangle = new Triangle(intArray[0], intArray[1], intArray[2]);

In fact, that is what your first error says, too:

C:\Users\Tier\Documents\NetBeansProjects\Triangle_Project\src\MyApplication.java:33: cannot find symbol
symbol : constructor Triangle(int,int,int)
location: class Triangle

Basically, you are calling a method that you never defined/declared. You have a no-arg constructor declared in the triangle class:

public Triangle() {}

You need something like this:

public Triangle(int side1, int side 2, int side3) 
{
   //code goes here that saves those passed values
   //but i'll let you try and figure out a little more
   //what is should be
}

[Menios Menelaos]

ACtually i can't figure out what i m doing so wrong. After some minor changes i get this errors

 init:
deps-jar:
Compiling 2 source files to C:\Users\Tier\Documents\NetBeansProjects\Triangle_Project\build\classes
C:\Users\Tier\Documents\NetBeansProjects\Triangle_Project\src\Triangle\MyApplication.java:41: cannot find symbol
symbol  : variable Side1
location: class Triangle.MyApplication
          intArray[0] = Side1;
C:\Users\Tier\Documents\NetBeansProjects\Triangle_Project\src\Triangle\MyApplication.java:42: cannot find symbol
symbol  : variable Side2
location: class Triangle.MyApplication
          intArray[1] = Side2; 
C:\Users\Tier\Documents\NetBeansProjects\Triangle_Project\src\Triangle\MyApplication.java:43: cannot find symbol
symbol  : variable Side3
location: class Triangle.MyApplication
          intArray[2] = Side3;
C:\Users\Tier\Documents\NetBeansProjects\Triangle_Project\src\Triangle\MyApplication.java:44: cannot find symbol
symbol  : constructor Triangle(int[])
location: class Triangle.Triangle
          Triangle Triangle = new Triangle(intArray);
4 errors
BUILD FAILED (total time: 0 seconds)
   

I ve also added the constructor but still no change.

           public Triangle (int s1,int s2, int s3)
{
     Side1 = s1; 
     Side2 = s2;
     Side3 = s3;
} 

[fred rosenberger]

It's very difficult to help you at this point, because we don't have access to what your code currently is. Even when you DO post it, it's hard to follow since there is so much of it.

Generally, the best way to code it to write as little as possible, compile it, and test it until you are SURE it works. THEN add another line or two of code.

You seem to have written 200 or so lines, and now it doesn't work, so it's VERY hard to track where the issues are.

Now, having said all that... The compiler seems to be complaining that on line 41 of the MyApplication.java file, you are trying to use the Side1 variable. WHERE is the Side1 variable declared?

[Menios Menelaos]

As a single program it works but i must have 2 java files.

My code right now

  
package Triangle;
import javax.swing.JOptionPane;
 
public class MyApplication {
 
/** Creates a new instance of myApplication */
public MyApplication() {
}
 
public static void main(String[] args  )
{
String message = "The Triangle Problem";
JOptionPane.showMessageDialog( null, message );
 
// obtain three integer values representing side lengths
int[ ] intArray = new int[ 3 ];
for( int i = 0; i < intArray.length; i++ )
{
message = "Enter an integer value for triangle side "
+ ( i + 1 ) + ":";
 
        // gather integer value representing side here…
        String input = JOptionPane.showInputDialog(null, message );
        intArray[i] = Integer.parseInt(input);
}
        // construct and evaluate the triangle
        Triangle triangle = new Triangle(intArray[0], intArray[1], intArray[2]);
        String outcome = Triangle.evaluate( );
 
          intArray[0] = Side1;             //Here is where i get the errors
          intArray[1] = Side2;             //Side doesn't seem to work for
          intArray[2] = Side3;             //some reason
          Triangle triangle = new Triangle(intArray);
          Triangle.evaluate();
 
// present the outcome to the user
JOptionPane.showMessageDialog( null, outcome );
}
}
 

&
The triangle.java is doing the math but i can't pass the values from Sides to intArrays back in MyApplication.java
Side1 = intArray[0] ;
Side2 = intArray[1] ;
Side3 = intArray[2] ;

package Triangle;
/**
* Triangle.java
*/
import javax.swing.JOptionPane;
 
 
public class Triangle
{
   private static int Side1, Side2, Side3 ;
       
 
      
        
        public Triangle (int s1 ,int s2, int s3)
{
     Side1 = s1; 
     Side2 = s2;
     Side3 = s3;
}
        
    
        private static void acceptThreeIntegers( )
    {
    String strSide1 = JOptionPane.showInputDialog( "Enter side 1: ");
        Side1 = Integer.parseInt( strSide1 );
        
    String strSide2 = JOptionPane.showInputDialog( "Enter Side 2: ");
        Side2 = Integer.parseInt( strSide2 );
        
    String strSide3 = JOptionPane.showInputDialog( "Enter Side 3: ");
        Side3 = Integer.parseInt( strSide3 );
    }
    
        private static void useMethod( )
    {
    if( checkForNegatives( ) == false )
    {
    if (checkForTriangle() == true)
    {    
       String result = evaluate( );
       JOptionPane.showMessageDialog( null, result );
    }
    else
       JOptionPane.showMessageDialog( null, "Impossible", "Results", JOptionPane.PLAIN_MESSAGE );   
    }
   else
       JOptionPane.showMessageDialog( null, "Impossible", "Results", JOptionPane.PLAIN_MESSAGE  );   
    
   }
   private static boolean checkForNegatives( )
    {
    if (Side1 <=0 || Side2 <=0 || Side3 <=0)
       return true;
    else return false; 
    }
    
/** evaluate if a triangle is physically possible*/
    private static boolean checkForTriangle( )
    {
    if (Side1 + Side2 - Side3 <=0 ||
        Side1 + Side3 - Side2 <=0 ||
        Side2 + Side3 - Side1 <=0)
    return false;
    else return true;
    }
 
 
    public static String evaluate( )
    {
    if (Side1 == Side2 && Side2 == Side3)
    {
    return "Equilateral";
    }
    if (Side1 == Side2 && Side2 != Side3 ||
        Side1 == Side3 && Side2 != Side3 ||
        Side2 == Side3 && Side1 != Side2)
    {
    return "Isosceles ";
    }
    if (Side1 != Side2 && Side2 != Side3 ||
        Side1 != Side2 && Side1 != Side3)
    {
    return "Scalene";
    }
    return "test value";
    }
    
    public  void main (String[] args)
    {
    acceptThreeIntegers( );
    useMethod( );
    }
  
    public static void Triangle (int[]intArray) {
        Side1 = intArray[0] ;
        Side2 = intArray[1] ;
        Side3 = intArray[2] ;
    }
 
}
       

Hope i made it as clear as possible

[Bill Shirley]

Originally posted by Menios Menelaos:
� accepts three integer values from the user and then evaluates them to see if they would correspond to an equilateral, isosceles, or scalene triangle. �

what do the three integers represent?
the lengths of the three sides, or are the inputs the 2D or 3D coordinates of the endpoints of the triangle's sides?

[Menios Menelaos]

No its just the length of the sides

[Paul Yule]

couple things...

you probably want to remove static from your triangle object everywhere it is used. I personally don't see a place where class level evaluations or variables should be used.
Once you make the methods and such specific to an instance of your triangle object I think your application class that holds your main will make more sense to you.

public static void Triangle (int[]intArray) {
        Side1 = intArray[0] ;
        Side2 = intArray[1] ;
        Side3 = intArray[2] ;
    }

I think this is suppose to be another constructor? Constructors don't have a return type and being static doesn't make a whole lot of sense. You may want to take some time to review this concept. I would think about how you want your object to be created and go with it, either via 3 ints or an int array holding 3 ints.
I would also remove all of the UI code in your Triangle object. Such as AcceptThreeIntegers and the JOptionPanes you have in there.
The following is what I have for your application class...notice the validateTriangle and evaluateType is tied to an instance of the object that was created.

    public static void main(String[] args) {
        JOptionPane.showMessageDialog(null, "The Triangle Problem");
        // obtain three integer values representing side lengths
        int[] intArray = new int[3];
        String message;
        for (int i = 0; i < intArray.length; i++) {
            message = "Enter an integer value for triangle side " + (i + 1) + ":";
            
            // gather integer value representing side here�
            String input = JOptionPane.showInputDialog(null, message);
            intArray[i] = Integer.parseInt(input);
        }
        // construct and evaluate the triangle
        Triangle myTriangleObject = new Triangle(intArray);
        if(myTriangleObject.validateTriangle()){
            String outcome = myTriangleObject.evaluateType();
            JOptionPane.showMessageDialog(null, outcome);
        }
        else{
            JOptionPane.showMessageDialog( null, "Impossible", "Results", JOptionPane.PLAIN_MESSAGE  );
        }
    }

[ October 28, 2008: Message edited by: Paul Yule ]

[Campbell Ritchie]

Agree the acceptThreeIntegers method should go, but the poster has been told to use JOptionPane throughout.

[Paul Yule]

Yea, I would use a scanner otherwise...I just meant remove it from the Triangle object.

[Campbell Ritchie]

Yes, I see what you mean.