help with java


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Thread: help with java

  1. #1
    Join Date
    Aug 2005
    Posts
    2

    help with java

    can i get some help with this java question please?

    "a cancellation error occurs when u are manipulating a very large number with a very small number. the large number may cancel out the smaller number. to obtain more accurate results the order of computation must be selected carefully.write a java program(with a main method) that compares the results of the summation for the following series computing from left to right and from right to left.

    1 + 1/2 + 1/3 + ..... + 1/n

    your program thgen should ask the user to enter a positive and greater than zero number, calculate the summation from left to right and from right to left and then display appropriate messages with the two calculated summations

    example test data:

    for n=50000 you should see:

    left to right summation: 11.397003949278504
    right to left summation: 11.397003949278519"

    thanx very much to anyone...in advance!!!!!

  2. #2
    Join Date
    Aug 2004
    Posts
    46
    can i get some help with this java question please?
    Sure. What kind of help do you need? What did you find confusing? What is preventing you from writing code that meets the requirements of the problem? You have to make known what you already know. Otherwise you're likely to get answers you don't understand.

    If you've begun work on this problem, please be a little more explicit about what you're doing, what you expect to happen, and what you actually observe.

    Please post a short, concise, executable example of what you're trying to do. This does not have to be the actual code you are using. Write a small example that demonstrates your intent, and only that. Wrap the code in a class and give it a main method that runs it - if we can just copy and paste the code into a text file, compile it and run it without any changes, then we can be sure that we haven't made incorrect assumptions about how you are using it.

    Post your code between [code] and [/code] tags. Cut and paste the code, rather than re-typing it (re-typing often introduces subtle errors that make your problem difficult to troubleshoot). Please preview your post when posting code.

    Please assume that we only have the core API. We have no idea what SomeCustomClass is, and neither does our collective compiler.

    If you have an error message, post the exact, complete error along with a full stack trace, if possible. Make sure you're not swallowing any Exceptions.

    Help us help you solve your problem.

  3. #3
    Join Date
    Aug 2005
    Posts
    2
    i've done this so far(below)...but when i try to put in the summation itself(1+1/2.....)it doesnt execute...how do i let the computer know that the summation is a series?


    public static void main(java.lang.String[] args) {

    double n;

    double firstSummation; //Calculate summation from left to right
    double secondSummation; //Calculate summation from right to left

    System.out.print(" Please enter a positive & greater than zero integer:");
    n=EasyIn.getDouble();
    if(n !=0 && n>0)
    {
    System.out.println(n);
    firstSummation=1+n;
    System.out.println("left-rightresult" + firstSummation);
    secondSummation=1+1/2+1/n;
    System.out.println("right-leftresult" + secondSummation);

    }
    else
    {
    System.out.println("error!");
    }
    }

  4. #4
    Join Date
    Dec 2004
    Location
    San Bernardino County, California
    Posts
    1,468
    Remember that you are either counting up from 1 to the number represented by "n" (left to right execution) or counting down from "n" to 1 (right to left).

    Does this counting up or counting down remind you of a commonly used control structure? Where you increment/decrement a counter and repeatedly execute the content until the counter reaches the set end point?

    Use this control structure (twice) to write your code. And keep in mind what arithmetic function you are performing to create the value which gets added to your total.
    Last edited by nspils; 08-30-2005 at 08:27 AM.

  5. #5
    Join Date
    Aug 2004
    Posts
    46
    What do you mean by "it doesn't execute"? Please be explicit about what you expect to happen, and what you actually observe. Also, when you post code next time, don't forget the [code] and [/code] tags.

    Note that your given code does not seem to reflect the assignment, especially with regard to the first summation.

  6. #6
    Join Date
    Aug 2005
    Posts
    17
    For left to right:
    Code:
    public static void main(java.lang.String[] args) 
    {
    
    	//define some variables
    	double n, firstSummation=0; 
    
    	//ask user for n
    	System.out.print(" Please enter a positive & greater than zero integer:");
    	n=EasyIn.getDouble();
    
    	//compute 1/1+1/2+1/3+...1/i + ... + 1/n (notice that in the formula i varies from 1 to n - for that reason the loop has i varying from 1 to n)
    	for(int i =1; i <=n; i++)
    	{
    		//add in the term 1/i into the sum
    		firstSummation += 1/i;
    	}
    
    	//print sum
    	System.out.println(firstSummation);
    }
    For more help, www.NeedProgrammingHelp.com


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