Question

methods

Answer 1

Hey

Answer 2

hey

Answer 3

Write a program that will read an arbitrary number of sets of triangle sides using only
integer values. The program should:
1. Prompt the user for sets of numbers and process them until the user submits the
numbers 0 0 0, which will terminate the program.
2. For each set of three numbers, the program should print the values read.
3. For each set of three numbers, the program should decide if the numbers represent
the sides of a valid triangle.
4. If the numbers could not represent a valid triangle, display an appropriate error
message.
5. If the numbers are valid, the program should determ

Answer 4

this is what i am working on

Answer 5

I want to create my own methods to calculate the Pythagorean Theorem, then do the side type and then angle type then print all the info about the triangle together.

Answer 6

so, how would I set up the part inside the method to make it so that it identifies it, but then doens't print anything until the end.

Answer 7

you can just call they pythagorean method at the end and print it there?

Answer 8

Right, but then I would be fitting in the angle and side classification to the Pythagorean method? So it would end up being just one method???

Answer 9

eh doesn't have to be. If you keep it as it is now, and just have the pythagorean method 'return' the information to the main method-- then you can manipulate that information when/where you want.

Answer 10

so how would I code that, as in how would I code so that the method returns the info to the main method?

Answer 11

```
public class HypotenuseCalc {
public static void main(String[]args) {
double hypotenuse = 0;
int side1 = 4;
int side2 = 3;
hypotenuse = pythag(side1, side2);
System.out.print(hypotenuse);
playWithHypotenuse(hypotenuse);
}
public static double pythag(int s1, int s2) {
return Math.sqrt((Math.pow(s1, 2)) + (Math.pow(s2, 2)));
}
public static void playWithHypotenuse(int hyp) {
int bignum = hyp*1000000;
System.out.println("\nHypotenuse*1million= " + bignum);
}
}
```
using methods is an art, and takes on more levels of meaning when you learn the significance of static, inheritance ect...

That may be the syntax, though I didn't explain what each part did exactly - let me know what parts you want me to clarify

Answer 12

note- change the parameter in method playWithHypotenuse to (double hyp) & change bignum to a double. Mistakes

Answer 13

You could make each triangle an object and have methods on it to say if it is valid or not. Or, yo can make a boolian method that returns true or false based on evaluation the triangle. Also, I don;t know why you said Pythagorean. It does not say these are right traingles.

Answer 14

true but the Pythagorean theorem also determines whether the angle is obtuse acute or right based on if a^2 + b^2 is equal to greater than or less than c^2

Answer 15

Is that the rest of #5? Cause that got cut off...

Answer 16

You could return a variable code or string. A numberic code would be 0 for invalid, 1 for accute, etc. A string would be just the descriptive word.

Answer 17

And, woodrow73
```
public static double pythag(int s1, int s2) {
return Math.sqrt((Math.pow(s1, 2)) + (Math.pow(s2, 2)));
```

That is not needed for the types of evaluations this is doing. A simple comparison of s1*s1 + s2*s2 to s3*s3.

Answer 18

Well, you need to find the longest (largest) first...

Answer 19

To solve the intial problem of determing if the three values makes a valid triangle I suggest that you take look at the Triangle Inequality Theorem.

Answer 20

yes, got that.

Answer 21

so how would I do a loop so that if an invalid triangle is given, I keep asking the user to input a correct value until valid output is given?

Answer 22

and how would I do a boolean so that if .... = true else = false sort of thing

Answer 23

By valid input for the triangles, would you be testing for whether 1) all 3 inputs are numbers 2) all 3 inputs are positive 3) all 3 inputs are not decimals?

Answer 24

& by your boolean statement- could you elaborate more?

Answer 25

You can use an if/else to get the results of the true/false. Might want to sort the input before sending to the method so you can say what the shorter and longer are if needed.

Answer 26

A boolean method, in general:
```
public static boolean someMethod(int a){
if (a > 5) return true;
return false;
}
```
This could be used in main code in the form of:
```
if someMethod(userInput) {
System.out.println("You input a number greater than 5.");
} else {
System.out.println("You input 5 or less.");
}
```
While this is a trivial example, I hope it shows how a boolean methiod can be used to trigger an if/else inside a different block of code.

A more common use of this would be using if a file handle opens, do the work on the flie but else send a message to the user that it was not valid.

Answer 27

@woodrow73 For any triangle, the sum of two sides cn not be shorter than the third.

Answer 28

a ha.. good point.

Answer 29

public class Triangle
{
public static boolean someMethod(int a, int b, int c){
if (a + b > c && b + c > a && a + c > b) return true;
return false;
}

public Triangle sideLengths (double side1, double side2, double side3)
{
System.out.println("Please enter the value for side 1.");
side1 = In.getDouble();
side2 = In.getDouble();
side3 = In.getDouble();
if someMethod
System.out.println("Please enter a valid number.");
else
System.out.print(side1 + side2 + side3);
}

Answer 30

public class TriangleClassification
{
public static void main [String [] args)
{
System.out.println("Please provide three side lengths of a triangle. Enter 0 0 0 to terminate the program.");
double side1 = In.getDouble();
double side2 = In.getDouble();
double side3 = In.getDouble();
}
do {
if (side1 == side2 == side3)
{
System.out.println("This triangle is equilateral.");
}
else if (side1 == side2 != side3 || side1 != side2 == side3 || side2 != side1 == side3)
{
System.out.println("This triangle is isoceles.");
}
else if (side1 != side2 != side3)
{
System.out.println("This triangle is scalene.");
}
else if (side1 <= 0 || side2 <= 0 || side3 <= 0)
{
System.out.println("Error! Invalid entry!");
{ while (side1 != 0 && side2 !=0 && side3 != 0);
{
System.out.println("The program was terminated by the user.");
}
}
//I have created a method to calculate the Pythagorean Theorem in order to determine whether the traingle is acute, obtuse or right.
public static double Pythagorean Theorem()
{
if (side1 > side2 && side1 > side3)
double c = side1;
double a = side2;
double b = side3;
else if (side2 > side1 && side2 > side3)
double c = side2;

else if (side3 > side1 && side3 > side2)
double c = side3;

if ((c*c) = Math.sqrt((a*a) + (b * b)));
{
System.out.println("This triangle is a right triangle.");
}
if ((c*c) < Math.sqrt((a*a) + (b*b)));
{
System.out.println("This triangle is an acute triangle.");
}
else
{
System.out.println("This triangle is obtuse.");
}
}

Answer 31

I realize that I need a loop for prompting the user and another loop around the whole program until program is terminated by user, and I have to put them together as methods, but I'm having some issues working that into what I have so far.

Answer 32

for starters - the closing bracket in your do - while loop is facing the wrong way --
should be:
```
} while(boo);
```
instead of:
```
{ while(boo);
```

Answer 33

and your do-while loop will continue looping as long as none of the 3 sides equal to 0.

Answer 34

In addition to what woodrow73 pointed out, you did your code as raw text. Sadly, raw text does not copy very well due to some issues with how information is displayed on OpenStudy.

If you put a ``` (the one with the ~ on the key) above and below the code, it fixes this. It also does code highlighting. Other ways of fixing this are to use http://dpaste.com/ or http://pastebin.com/

Without being able to copy the code, it can be hard to test it.

Answer 35

public boolean isIsosceles()
if (side1 == side2 != side3 || side2 == side3 != side1|| side1 == side3 != side2)
{
return true;
}
else
{
return false;
}

Answer 36

@e.mccormick would this be acceptable? To do a boolean method for each classification (isoceles, equilateral and scalene, obtuse, acute and right angle) and then at the end have it print Ex: You triangle is obtuse and isoceles. If so, how would I go about doing that at the end?

Answer 37

You could just return the type as a string and use one function to type them. Inside it, if it needs helpers, that is fine too.

Answer 38

Right, it would be returned at the end as a string though but I couldn't just do this kind of setup because then it would print the classifications at different times, right?
if (side1 == side2 == side3)
{
System.out.println("This triangle is equilateral.");
}
else if (side1 == side2 != side3 || side1 != side2 == side3 || side2 != side1 == side3)
{
System.out.println("This triangle is isoceles.");
}
else if (side1 != side2 != side3)
{
System.out.println("This triangle is scalene.");
}
else if (side1 <= 0 || side2 <= 0 || side3 <= 0)
{
System.out.println("Error! Invalid entry!");

Answer 39

So how would you recommend approaching this problem using methods?

Answer 40

You can return a string. Don't print it. Return it.

Answer 41

As an incomplete example:

```
public String triangleType(int a, int b, int c) // or whatever your inputs are
{
\\ if some evaluation
return new String("equilateral")
\\ else if some evaluation
return new String("scalene")
\\ else if some evaluation
return new String("invalid")
}
```

That will just pass back a word. So you make a string in the main method or whatever that is the typeOfTriangle.

typeOfTriangle = triangleType(5, 10, 7)

Perhaps the input will need to be angles or the order things are put in may need to be highest to lowest.

Answer 42

Ok, so after I have created all of these methods for classification, I can just return them in the main method like you said, and enclose the entire program with a do while loop if I want the program to keep repeating until the user enters 0 0 0 in which case it would be termianted?

Answer 43

Yah.

So all the main has is the while loop and calls to the other methods.

Answer 44

To be object based, each triangle under evaluation would be an object with methods to talk about it... but for what you are doing, static methinds should work very well and are probably less coding!

Answer 45

Yes! Thank you!

Answer 46

So here is what I have up to this point
public class Triangle
{
public static void main (String [] args)
{

public static void setSides()
{
System.out.println("Please enter three side lengths for a triangle. Enter 0 0 0 to terminate the program.");
int side1 = In.getInt();
int side2 = In.getInt();
int side3 = In.getInt();
}
public static void isPossible()
if (side1 + side2 > side3 && side2 + side3 > side1 && side1 + side3 > side2)
{
return true;
}
else
}
return false;
}
public String sideType(int side1, int side2, int side3)
{
\\ if (side1 == side2 == side3)
return new String("equilateral")
\\ else if (side1 != side2 != side3)
return new String("scalene")
\\ else if (side1 == side2 != side3 || side2 == side3 != side1 || side1 == side3 != side2)
return new String("isoceles")
}

public String angleType (int side1, int side2, int side3)
{
if (side1*side1 + side2*side2 == side3*side3 || side1*side1 + side3*side3 == side2*side2 || side2*side2 + side3*side3 == side1*side1)
return new String("right angle")
else if (side1*side1 + side2*side2 > side3*side3 || side1*side1 + side3*side3 > side2*side2 || side2*side2 + side3*side3 > side1*side1)
return new String("acute")
else if (side1*side1 + side2*side2 < side3*side3 || side1*side1 + side3*side3 < side2*side2 || side2*side2 + side3*side3 < side1*side1)
return new String("obtuse")
}
So, in order for the program to check, after receiving input is the triangle is possible before moving on and printing an error message accordingly, should this be part of the the setSide value, or should I have isPossible as part of my if statements in the other methods, or how would that work?

Answer 47

Well, in mine, I did that as comments, so the cod won't work. It was just a template for you to see how you could go about it. You need real code rather than comments. Hehe.

Also, it is basically impossible to read the code in a post. And if I try to copy it out, it becomes one line because you don't use the code highlighting system...

Answer 48

See, to me, your code becomes:
public class Triangle { public static void main (String [] args) { public static void setSides() { System.out.println("Please enter three side lengths for a triangle. Enter 0 0 0 to terminate the program."); int side1 = In.getInt(); int side2 = In.getInt(); int side3 = In.getInt(); } public static void isPossible() if (side1 + side2 > side3 && side2 + side3 > side1 && side1 + side3 > side2) { return true; } else } return false; } public String sideType(int side1, int side2, int side3) { \\ if (side1 == side2 == side3) return new String("equilateral") \\ else if (side1 != side2 != side3) return new String("scalene") \\ else if (side1 == side2 != side3 || side2 == side3 != side1 || side1 == side3 != side2) return new String("isoceles") } public String angleType (int side1, int side2, int side3) { if (side1*side1 + side2*side2 == side3*side3 || side1*side1 + side3*side3 == side2*side2 || side2*side2 + side3*side3 == side1*side1) return new String("right angle") else if (side1*side1 + side2*side2 > side3*side3 || side1*side1 + side3*side3 > side2*side2 || side2*side2 + side3*side3 > side1*side1) return new String("acute") else if (side1*side1 + side2*side2 < side3*side3 || side1*side1 + side3*side3 < side2*side2 || side2*side2 + side3*side3 < side1*side1) return new String("obtuse") }

Answer 49

oh ok let me fix that. Also, wouldn't your template work though the same way except without comment slashes?

Answer 50

I am using a third party, dr. java so I just attached it since it doesn't really work using copy paste

Answer 51

If you put ``` above and below, the copy paste works fine...

Answer 52

```
public class Triangle
{
public static void main (String [] args)
{

public static void setSides()
{
System.out.println("Please enter three side lengths for a triangle. Enter 0 0 0 to terminate the program.");
int side1 = In.getInt();
int side2 = In.getInt();
int side3 = In.getInt();
}
public static void isPossible()
if (side1 + side2 > side3 && side2 + side3 > side1 && side1 + side3 > side2)
{
return true;
}
else
}
return false;
}
public String sideType(int side1, int side2, int side3)
{
\\ if (side1 == side2 == side3)
return new String("equilateral")
\\ else if (side1 != side2 != side3)
return new String("scalene")
\\ else if (side1 == side2 != side3 || side2 == side3 != side1 || side1 == side3 != side2)
return new String("isoceles")
}

public String angleType (int side1, int side2, int side3)
{
if (side1*side1 + side2*side2 == side3*side3 || side1*side1 + side3*side3 == side2*side2 || side2*side2 + side3*side3 == side1*side1)
return new String("right angle")
else if (side1*side1 + side2*side2 > side3*side3 || side1*side1 + side3*side3 > side2*side2 || side2*side2 + side3*side3 > side1*side1)
return new String("acute")
else if (side1*side1 + side2*side2 < side3*side3 || side1*side1 + side3*side3 < side2*side2 || side2*side2 + side3*side3 < side1*side1)
return new String("obtuse")
}
```

Like that.

Answer 53

Your scaline test is flawed.

Answer 54

With that order, something can be isoceles but reported as scalene.

Answer 55

oops yeah, I'll fix that. Thanks for catching that. So, to follow up with what you said before, would the sideType and angleType work ok as they are?

Answer 56

Is this an integer based program? No float/double?

Answer 57

I ask because == and floating point do not play nice.

Answer 58

yes, this is integer based thankfully

Answer 59

Well, do some test cases and see what you get. Rather than use input, you can do a test harness... as in call the functions with predefined valyes and just print the reuslts. If one breaks, you know what broke it.

Answer 60

I keep getting an error message when trying to compile before each new method saying illegal start of expression.

Answer 61

I'm also getting class interface and enum expected before the methods

Answer 62

Does dr. java gibe any pre-cmpile error help?

Answer 63

enum expected generally means it thinks you need something to be declared. It can also mean something is mispelled.

Answer 64

no, unfortunately it provides no error help. Let me check for any undeclared variables.

Answer 65

If that is the entire code, I can toss it into Eclipse.

Answer 66

That would be great if you could, also do you think this would be caused by having multiple methods with int side1, int side2 and int side3??

Answer 67

No, they are local to each.

Answer 68

right, ok good that's what I thought.

Answer 69

There is a lot missing to this code.... hmmm....

int side1 = In.getInt();

But I do not see In.

Answer 70

oh i think that is in the java utilities package so I should probably put that at the start of the program.

Answer 71

Yep, and that would be enumerating it...

Answer 72

public static void isPossible()

You have a return in that. Voids can't return anything. If you need to to return true, it must be a bool, and if it needs to return an int it must be an int, etc.

public static int isPossible(){
bla
return some_int
}

public static double isPossible(){
bla
return some_double
}

those are "valid" as opposed to the void with a return.

Answer 73

ok so if I were to have the method return true as a boolean, how would I make it so that an error message pritns right after input is given saying that the triangle is not possible instead of continuing on with the rest of the program?

Answer 74

You need some sort of end condition that is triggered by the return of the bool. Like an if statement that breaks the while loop if it returns false.

Answer 75

Or if it returns true... It depends on the method.

Break on a true result:
if (is_bad()) break;

Break on a false result
if (is_good() == false) break;

Answer 76

ok let me try that

Answer 77

Are they having you import some class for all the projects you make?

Answer 78

I ask, cause usually inpit from the user needs something like:

Scanner sc=new Scanner(System.in);
int side1 = sc.nextInt();
int side2 = sc.nextInt();
int side3 = sc.nextInt();

Answer 79

yes they are having us import it for all projects so far but like you said the scanner is what is usually used.

Answer 80

OK, then that other package must have things like In, which is why Eclipse is yelling at me. LOL.

Answer 81

Yes! it does contain In, but it still beats at least pasting the entire In file in before every program lol

Answer 82

Yes, code reuse is important. but custom libraries mean my IDE does not know everything it needs to debug this.

Answer 83

hmm.... it's not liking my code so far. 25 errors lol

Answer 84

Well, rememebr that the class holds everything and that your main only holds itself. The other methofds are inside the class but outside the main.

Answer 85

```
import java.util.Scanner;
public class trianglef {

public static void main(String[] args) {



double sidea;
double sideb;
double sidec;


Scanner in = new Scanner(System.in);
System.out.println("Enter the first side of a triangle: ");
sidea = in.nextDouble();
System.out.println("Enter the second side of a triangle: ");
sideb = in.nextDouble();
System.out.println("Enter the third side of a triangle: ");
sidec = in.nextDouble();


if (((sidea + sideb) <= (sidec)) ||((sidea + sideb) <= (sideb)) ||((sideb +sidec) <= (sidea)))
do {
System.out.println("Not a traingle. Please try again");
sidea = in.nextDouble();
sideb = in.nextDouble();
sidec = in.nextDouble();
} while (sidea + sideb <= sidec || sidea + sidec <= sideb || sideb + sidec <= sidea);


System.out.println("Sides" + " " + sidea + " " + sideb + " " + sidec);

if (((sidea * sidea) + (sideb * sideb)) == (sidec * sidec))
System.out.println("right triangle");
if (((sidea * sidea) + (sidec * sidec)) == (sideb * sideb))
System.out.println("right triangle");
if (((sidec * sidec) + (sideb * sideb)) == (sidea * sidea))
System.out.println("right triangle");

//right triangle

if ((sidea == sideb) && (sidea == sidec) && (sideb == sidec))
System.out.println("equilateral triangle");

//equilateral triangle

if (((sidea == sideb) || (sideb == sidec) || (sidea == sidec)) && !((sidea == sideb) && (sidea == sidec) && (sideb == sidec)))
System.out.println("isosceles triangle");


else if (!((sidea == sideb) && (sidea == sidec) && (sideb == sidec)))
System.out.println("scalene triangle");

//scalene
if (sidea*sidea + sideb*sideb == sidec*sidec || sidea*sidea + sidec*sidec == sideb*sideb || sideb*sideb + sidec*sidec == sidea*sidea)
System.out.println("right angle");
else if (sidea*sidea + sideb*sideb > sidec*sidec || sidea*sidea + sidec*sidec > sideb*sideb || sideb*sideb + sidec*sidec > sidea*sidea)
System.out.println("acute");
else if (sidea*sidea + sideb*sideb < sidec*sidec || sidea*sidea + sidec*sidec < sideb*sideb || sideb*sideb + sidec*sidec < sidea*sidea)
System.out.println("obtuse");

}
}
```

Answer 86

This is the code I have so far because I couln't get it to work when it was individual methods so how would I change the code above so that it uses method overloading?

Answer 87

It would be hard to have multiple methods 'overloaded' because you would always have the same parameters.

I'd either make multiple methods.. one called testEquilateral() one called testIsosceles() or make a big method that you call once & have it return an int getTriangleInfo() method - could return 1 for equilateral -- 2 for Isosceles -- 3 for scalene.

Answer 88

Ok I'll try that. I had that before and when I try to compile I get a lot of "illegal start of the expression" at the start of each method. So each method would be set up like public static void isEquilateral() for instance and then in the main method I would just be doing
public static void main (String [] args)
{
isequilateral()
isIsoceles()
isScalene()
}
?
And then how would I set up a final print statement to print the side type, angle type and side lengths entered together?

Answer 89

well, for those methods to actually test the triangle, you have to put the 3 int values in the method arguments; such as:
```
isequilateral(sidea, sideb, sidec);
isIsoceles(sidea, sideb, sidec);
isScalene(sidea, sideb, sidec);
```
don't forget the semi-colons at the end & in order to get the information, the methods should return a boolean variable, as to whether it is equilateral/isosceles/scalene

Answer 90

This requires special 'syntax' when you actually make the method too - since you will need to make sure it a) has a return value && b) takes 3 ints into it's parameters

Answer 91

so the return value would be a string in these cases because I want it to return a print statement at the end? So public static String isEquilateral(); for instance?

Answer 92

Ya, that works.