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Java Forum / General / January 2007What is the problem in this program?
//program to find the roots of a quadratic eqaution import java.io.*; public class quadratic_roots { int r1,r2; public void accept(int a,int b,int c) { r1=-b/2a+(math.sqrt(b*b-4ac))/2a; r2=-b/2a-(math.sqrt(b*b-4ac))/2a; System.out.println(r1+" , "+r2); } } > //program to find the roots of a quadratic eqaution > [quoted text clipped - 10 lines] > } > } It doesn't compile and it has redundant imports. Dan.  SignatureDaniel Dyer http://www.uncommons.org What do you mean? > What do you mean? What do you want to hear? You haven't given any indication of the problem that you are having. If you are getting an error at compile time or at runtime you should post the error message. Or if the result of the program is wrong you should indicate how it is wrong. The only two things that were immediately obvious as "wrong" were the ones I mentioned. The code will not compile, "math.sqrt" is invalid. The Math class begins with an uppercase letter. I'm guessing this is the problem that you want help with because until you've fixed this you won't make any further progress. You are importing every class in the java.io package but not using any of them. This won't stop your code from working but it is unnecessary. Dan. SignatureDaniel Dyer http://www.uncommons.org f2prateek schreef: > What do you mean? Please quote some content when replying. He means that it doesn’t compile and contains redundant imports. Look up those words in a dictionary if you don’t understand them. Furthermore, it does not follow style conventions. H. - -- Hendrik Maryns http://tcl.sfs.uni-tuebingen.de/~hendrik/ ================== http://aouw.org Ask smart questions, get good answers: http://www.catb.org/~esr/faqs/smart-questions.html Sorry i did not post the error my program.The error it is showing is it needs a ';' and higlights the line: r1=-b/2a+(math.sqrt(b*b-4ac))/2a; Hi, > Sorry i did not post the error my program.The error it is showing is it > needs a ';' and higlights the line: > > r1=-b/2a+(math.sqrt(b*b-4ac))/2a; Note that (besides the other errors), you must - in contradiction to the mathematical notation - explicitely write the multiplication *! Ciao, Ingo > Sorry i did not post the error my program.The error it is showing is it > needs a ';' and higlights the line: > > r1=-b/2a+(math.sqrt(b*b-4ac))/2a; You do not seem to be listenning carefully to what you are being told. I recall Daniel mentioned that 'math.sqrt' should be 'Math.sqrt'. Why did you not check that method in the JavaDocs? (Have you heard of the JavaDocs?) The line should be more like this, in any case.. r1=-b/(2*a)+(Math.sqrt(b*b-4*(a*c)))/(2*a); Note that '2a' is not understood by Java as being 2*a the programmer needs to write the '*' specifically. It also helps to use more brackets, in order to ensure that the multiplications and divisions are done in the order you wish. I may have got the brackets wrong in the above example. Then, when those problems are fixed, you need to fix a 'possible loss of precision'. It seems you are very new to Java. A good group for those new to Java is comp.lang.java.help. Also, if you haven't discovered them yet, look around for the JavaDocs and the Java tutorial. I think both would be a great help to you. You were given a number of good tips by the other replies on this thread - please review them all carefully. HTH Andrew T. I have tried all the variations you have told me,including the 'M' capital in Math.sqrt .I accidentally omitted the * in the multiplication calculation in the program i submitted to you. //program to find the roots of a quadratic eqaution import java.io.*; public class quadratic_roots { float r1,r2; public void accept(int a,int b,int c) { r1=-b/2*a+(Math.sqrt(b*b-4*a*c))/2*a; r2=-b/2*a-(Math.sqrt(b*b-4*a*c))/2*a; System.out.println(r1+" , "+r2); } } now it's showing me possible loss of precision in the line: r1=-b/2*a+(Math.sqrt(b*b-4*a*c))/2*a; Sorry.Some typing mistake again. My program is: //program to find the roots of a quadratic eqaution import java.io.*; public class quadratic_roots { float r1,r2; public void accept(int a,int b,int c) { r1=-b/(2*a)+(Math.sqrt(b*b-4*(a*c)))/(2*a); r2=-b/(2*a)-(Math.sqrt(b*b-4*(a*c)))/(2*a); System.out.println(r1+" , "+r2); } } It is showing me 'possible loss of precision' in the line: r1=-b/(2*a)+(Math.sqrt(b*b-4*(a*c)))/(2*a); > Sorry.Some typing mistake again. You are doing a number of mistakes at the moment in terms of getting people to *want* to help you. 1st of all - do not waste our time with typing mistakes. Always copy/paste both code and compiler or runtime errors. *Always*. Next - you seem to have ignored me when I asked you to review this thread carefully. You are still making mistakes that others have already mentioned, and it is obvious from your flurry of replies that you did not even read my post carefully. As such - I will make no further posts on this thread. See you over on c.l.j.help, if you should choose to post there. Andrew T. > Sorry.Some typing mistake again. > My program is: [quoted text clipped - 14 lines] > It is showing me 'possible loss of precision' in the line: > r1=-b/(2*a)+(Math.sqrt(b*b-4*(a*c)))/(2*a); You've gotten far enough along here that you're starting to deal with errors that are a bit more specific to Java that to programming in general, but you really need to get some background in basic elements of the language. You've got two immediate things to worry about. The first term on the right of the equality involves integer division. This likely doesn't do what you want in Java. E.g., what do you think int x = 3 double y = x/2; System.out.println(y) prints out? It's not 1.5. The second issue-- which is causing your current error message -- involves what happens in a computer program when the arguments to an operator involves different data types. In Java Math.sqrt always returns a 'double'. You are adding this to an 'int' value. Java's rule is that the integer argument is converted to a double and you get a double result. In the end you try to save this as a float (in r1 or r2). Since floats have less precision than doubles, Java does not allow you to do this without an explicit cast. There are some other issues you may want to think about -- what happens when the discriminant is negative? But before getting into such subtleties you need to spend some time learning basic Java to understand how it does arithmetic and coversions amongst the arithmetic types. Regards, Tom McGlynn >> Sorry i did not post the error my program.The error it is showing is it >> needs a ';' and higlights the line: [quoted text clipped - 11 lines] > > r1=-b/(2*a)+(Math.sqrt(b*b-4*(a*c)))/(2*a); Yup, it's correct, but one inefficiency that can be taken out is the dividing by 2a twice, since: -b sqrt(b^2 - 4ac) -- +/- ---------------- 2a 2a is equal to: -b +/- sqrt(b^2 - 4ac) --------------------- 2a lex In a previous article, "f2prateek" <f2prateek@gmail.com> said: >What do you mean? Why don't you ask your teacher, since that's the person who is getting paid to answer your questions? SignaturePaul Tomblin <ptomblin@xcski.com> http://blog.xcski.com/ Alright. Talk. Don't make me reach over there and pull your still-pumping heart out from the gaping hole you used to call a chest whilst breaking your sternum and playing air guitar with your ribcage. -- Tai The program I have given you is much more advanced than what the ICSE board want the students to learn till the ninth..it will be of a higher level in tenth...I am just making this program to make finding the roots in my maths faster and easier.And since 20 mks are in my teachers hand.who probably will not understand what I am trying to do or what to do....I don't want to offend her. > //program to find the roots of a quadratic eqaution Note that the original poster took my recommendation to post over at c.l.j.help, but ended up solving the 'loss of precision' problem themselves. There are a lot of things the OP might yet benefit to learn about posting/asking questions, and Java, but I think the same can be said, of most of us. Andrew T. 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