Quoting Post Archived Topic: It will not be bumped to the top of the forum. Topic Java Membername   Not a member? Sign Up Free (takes 20 seconds) Password   Forgotten your password? Post Font: Verdana Arial Black Georgia Comic Sans Impact   Size: Tiny Normal Big Huge   Color: Default Dark Red Red Orange Brown Green Olive Cyan Blue Dark Blue Indigo Black [ Check Spelling ] [ Post Preview ] [ LiveTags ] Quote: from [m]squirellplayingtag[/m] at 12:13 pm on Sep. 24, 2004[quote]Yea I figured it out. Turns out I forgot to call two methods which didn't set 2 variables. Opps. I thought that I could call them from inside another method, while returning the numbers which didn't work. Or something like that, I got it straightened out now. Thanks for the heads up. I sorta understand it, but I'm sure I'll grasp it better once we get more into it. [/quote] FAQ Keyword Search: Post Options Favorites Manager Notify me of new replies to this topic by email Notify me of new replies to this topic by private message Original Post squirellplayingtag Posted at 12:27 pm on Sep. 23, 2004 I worked on this all day today and can not figure out why it returns 0 for some of them. Code: /**  @Author: Dave O\'Brien     Date: Sep 23, 2004  Teacher:      Lab:     Misc: */ import apcslib.*; // formatting import chn.util.*; // Input Console public class Polygon  {       public static void main(String args[]) {               /*ConsoleIO input = new ConsoleIO();               System.out.print(\"Number of sides: \");               int sides = input.readInt();               System.out.print(\"Length of each side: \");               double length = input.readDouble();               RegularPolygon polly = new RegularPolygon(sides, length);*/               RegularPolygon polly = new RegularPolygon(4, 10);               System.out.println("Radius of circumscribed circle = " + polly.getr());               System.out.println("Radius of inscribed circle = " + polly.getR());               System.out.println("Vertex angle = " + polly.vertexAngle());               System.out.println("Perimeter = " + polly.Perimeter());               System.out.println("Area = " + polly.Area());       } } class RegularPolygon {  private int myNumSides;        // # of sides  private double mySideLength;   // length of side  private double myR;            // radius of circumscribed circle  private double myr;            // radius of inscribed circle  // constructors  public RegularPolygon()  {       myNumSides = 4;       mySideLength = 2;  }  public RegularPolygon(int numSides, double sideLength)  {       myNumSides = numSides;       mySideLength = sideLength;  }  // private methods  private void calcr()  {       myr = 1.0/2*mySideLength*(cot(Math.toRadians(180.0)/myNumSides));  }  private void calcR()  {       myR = 1.0/2*mySideLength*(csc(Math.toRadians(180.0)/myNumSides));  }  // public methods  public double vertexAngle()  {       return ((myNumSides -2.0)/myNumSides)*180.0;  }  public double Perimeter()  {       return myNumSides*mySideLength;  }  public double Area()  {       return 1.0/2.0*myNumSides*(myR*myR)*(double)Math.sin(2.0*Math.toRadians(180.0)/(double)myNumSides);  }  public double getNumside()  {       return myNumSides;  }  public double getSideLength()  {       return mySideLength;  }  public double getR()  {       return myR;  }  public double getr()  {       return myr;  }  public double csc(double x)  {       return 1.0/Math.sin(x);  }  public double cot(double x)     {       return 1.0/Math.tan(x);  } } I assume a math function returns something like 0.32 as an int so when multiplied I get 0. I've tried putting (double) everywhere and nothing works. I figured the people who know java know more about it then me and my classmates. The part I'm on is this. # Write a testing class with a main() that constructs a RegularPolygon and calls each method. A sample run of the program for a polygon with 4 sides of length 10 would give: number of sides = 4 length of side = 10.00 radius of circumscribed circle = 7.07 radius of inscribed circle = 5.00 vertex angle = 90.0 perimeter = 40.00 area = 100.00

Replies squirellplayingtag Posted at 3:39 am on Oct. 27, 2004 I do use long variable names when making my own, but the labs give me the variable names as well as a basic outline so I just keep it. sakurag Posted at 8:03 pm on Oct. 25, 2004 Quote: from Suke at 12:47 pm on Oct. 25, 2004 Also you need to probably choose better variable names for example Code: private double myR;            // radius of circumscribed circle private double myr;            // radius of inscribed circle Java supports long variable names for this reason.. you should probably try something more descriptive. Code: private double radiusCircumscribed; private double radiusInscribed; I didn't look at what you are doing with the vars so there may be a better name, I just used what I could make from the description of it. Also it's not good to have the var the same but just different capitolization.. that would lead to confusion.  It should be easy for someone else to understand your code and not have to be confused with such things as same name of variables with different capitol letters. (Edited by Suke at 2:50 pm on Oct. 25, 2004) I agree with you here, this is me being lazy typing code into livewire. I usually use Hungarian notation for my code.  For those of you who don't know, Hungarian notation precedes each variable name with an abbreviation for the type. ie. nWidth - Integer type lpPoint - Long pointer type sz       - string type, 0 terminated hDC    - win32 HANDLE etc, etc, etc. Long names provides better readability + more typing ;]  Though.. I sometimes write cryptic code ;] Code: (*Rn) = 3.0F * ( (*(RPtn + (*(Ptn + 1)))) - (*(RPtn + (*(Ptn + (N - 1))))) ); sakurag Posted at 7:57 pm on Oct. 25, 2004 Quote: from Suke at 12:41 pm on Oct. 25, 2004 Quote: from sakurag at 11:31 pm on Sep. 23, 2004 Note: If you are going to use a constant like 1.0, if you'd like to make it explicitly a double or a float, you can use F or D(I think). such as, Code: float x = 1.0F + 1.2F; This is garbage imo.. even if it does work it's unnecessary as a decimal is assumed as a double. for example 10/3 = 3 (integer division) However 10/3.0 = 3.3333  (treated as a double) (Edited by Suke at 2:52 pm on Oct. 25, 2004) I disagree.  For instance, what if the data type you are using is a float.  Unless you explicitly say it is, you will have to type cast it later in order to get rid of warnings. Code: struct Point {  public float x;  public float y;  public float z; } ... ptMyPoint.x = 10/3.0; // downcast, may cause unexpected results ptMyPoint.x = 10.0F / 3.0F; // No casting necessary for(i = 0; i < 500000000000; i++) {   ptMyPoint.x = (float)(10/3.0); } // Explicit cast 500000000000 times, depending on compiler, EXTREMELY inefficient. In my line of practice(though usually C), I try to be as precise as possible with my code.  I also try to avoid any uneccessary processor power, ie downcasting.  (I think upcasting is usually fine, but may eat cpu time). Of course, we all program differently.   Suke Posted at 12:47 pm on Oct. 25, 2004 Also you need to probably choose better variable names for example Code: private double myR;            // radius of circumscribed circle private double myr;            // radius of inscribed circle Java supports long variable names for this reason.. you should probably try something more descriptive. Code: private double radiusCircumscribed; private double radiusInscribed; I didn't look at what you are doing with the vars so there may be a better name, I just used what I could make from the description of it. Also it's not good to have the var the same but just different capitolization.. that would lead to confusion.  It should be easy for someone else to understand your code and not have to be confused with such things as same name of variables with different capitol letters. (Edited by Suke at 2:50 pm on Oct. 25, 2004) Suke Posted at 12:41 pm on Oct. 25, 2004 Quote: from sakurag at 11:31 pm on Sep. 23, 2004 Note: If you are going to use a constant like 1.0, if you'd like to make it explicitly a double or a float, you can use F or D(I think). such as, Code: float x = 1.0F + 1.2F; This is garbage imo.. even if it does work it's unnecessary as a decimal is assumed as a double. for example 10/3 = 3 (integer division) However 10/3.0 = 3.3333  (treated as a double) (Edited by Suke at 2:52 pm on Oct. 25, 2004) sakurag Posted at 9:16 am on Oct. 25, 2004 Quote: from the real anti christ at 8:27 pm on Oct. 22, 2004 The Code: this. method seems unnecessary he doesn’t need that constructor to set anything because the radius will always be reset for each time the prog is run and there is no reason to change the initial value after the user gives input (or the program generates a test case) . Fyi for those that don’t know Code: this. Allows variables to evaluate them self’s, in other words (this var = the value of the argument var sent in) The keyword Code: this can be completely omitted from any Java code.  The thing is, it allows for a better way to name your member variables. For example, you have a member variable Code: szFilename You have a function which sets the file name. What do you name the param. you pass in? The this keyword allows you to name them the same name.  Of course, I've never tried to just say x = x; instead of this.x = x, so I don't know if it can tell, but I doubt it. I suppose it's up to you what you do.  I do this in c++ as well. the real anti christ Posted at 8:27 pm on Oct. 22, 2004 The Code: this. method seems unnecessary he doesn’t need that constructor to set anything because the radius will always be reset for each time the prog is run and there is no reason to change the initial value after the user gives input (or the program generates a test case) . Fyi for those that don’t know Code: this. Allows variables to evaluate them self’s, in other words (this var = the value of the argument var sent in) sakurag Posted at 1:58 pm on Sep. 24, 2004 Another thing to consider is to calculate the areas and perimeters when you set the values of the sides and what not.  This way, you will only ever need to calculate them once, if you decide to call the gat 100 times squirellplayingtag Posted at 12:13 pm on Sep. 24, 2004 Yea I figured it out. Turns out I forgot to call two methods which didn't set 2 variables. Opps. I thought that I could call them from inside another method, while returning the numbers which didn't work. Or something like that, I got it straightened out now. Thanks for the heads up. I sorta understand it, but I'm sure I'll grasp it better once we get more into it. sakurag Posted at 9:31 pm on Sep. 23, 2004 Code: /** @Author: Dave O\'Brien    Date: Sep 23, 2004 Teacher:     Lab:    Misc: */ import apcslib.*; // formatting import chn.util.*; // Input Console public class Polygon  {      public static void main(String args[]) {              /*ConsoleIO input = new ConsoleIO();              System.out.print(\"Number of sides: \";              int sides = input.readInt();              System.out.print(\"Length of each side: \";              double length = input.readDouble();              RegularPolygon polly = new RegularPolygon(sides, length);*/              RegularPolygon polly = new RegularPolygon(4, 10.0D);              System.out.println("Radius of circumscribed circle = " + polly.getr());              System.out.println("Radius of inscribed circle = " + polly.getR());              System.out.println("Vertex angle = " + polly.vertexAngle());              System.out.println("Perimeter = " + polly.Perimeter());              System.out.println("Area = " + polly.Area());      } } class RegularPolygon { public const int DEF_NUM_SIDES = 4; public const double DEF_SIDE_LENGTH = 2.0D; private int numSides;        // # of sides private double sideLength;   // length of side private double rCircum;            // radius of circumscribed circle private double rInscrib;            // radius of inscribed circle // constructors public RegularPolygon( ) {      numSides = DEF_NUM_SIDES;      sideLength = DEF_SIDE_LENGTH; } public RegularPolygon(int numSides, double sideLength) {      // gs Note: you might want to put checks, ie      /*      if(numSides > 0) {         this.numSides = numSides;      }      else      {         this.numSides = DEF_NUM_SIDES;      }      */      this.numSides = numSides;      this.sideLength = sideLength; } // private methods private void calcr() {      this.rInscrib = 1.0D / 2.0D * this.mySideLength * ( this.cot( Math.toRadians(180.0D) / (double)myNumSides)); } private void calcR() {      this.rCircum = 1.0D / 2.0D * this.mySideLength * ( this.csc( Math.toRadians(180.0D) / (double)myNumSides)); } // public methods public double vertexAngle() {      return ( (this.numSides - 2.0D) / (double) myNumSides) * 180.0; } public double Perimeter() {      return (double)this.numSides * this.sideLength; } public double Area() {      return 1.0D / 2.0D * (double)this.numSides * ( this.rCircum * this.rInscrib ) * (double)Math.sin(2.0D * Math.toRadians(180.0D) / (double)myNumSides); } public int getNumside( ) {      return this.numSides; } public double getSideLength() {      return this.mySideLength; } public double getR() {      return this.rCircum; } public double getr() {      return this.rInscrib; } public double csc(double x) {      return 1.0D / Math.sin(x); } public double cot(double x)    {      return 1.0D / Math.tan(x); } I would like you note that some of the things you do are a little weird to me.  That asside, I have rewritten some of your code, I don't know if it compiles or runs correctly, since I do not have a java compiler on my computer right now. Note: If you are going to use a constant like 1.0, if you'd like to make it explicitly a double or a float, you can use F or D(I think). such as, Code: float x = 1.0F + 1.2F; Also, if you are using a class, like you are go ahead and name your data members whatever you want. Code: private double radius; Then if you need to set the radius, do this. Code: public void setRadius(double radius) {   this.radius = radius; } This gets you away from, 'myradius' or whatever. I hope this helps you're problem. All 10 previous replies displayed.