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  1. #1
    juvenchan is offline Member
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    Default Need Help For doing if else statement

    First of all, I never learn any java or C programming.. so I am new to any programming.

    I got an assignment with skeleton provided from professor, but there are errors and I do not know how to fix it.
    It is really easy to you guys.. right?
    I want to finish this assignment so that I can focus on my other classes..
    i will also post what I wrote in #2:D
    Thanks for helping me...:o
    He gave us simple instruction, input and desire output which are the following:



    From Prof. :This assignment will give you practice with if statements, strings, polynomials of degree 2 and Math.sqrt.

    The file available on the Web page is the main(). I have written some of it and you must complete it. The sections to be
    completed are marked // Complete.

    I will run your program using the input file posted on the Web page. Your output must match the desired output posted on the Web page. Be sure to test the following values:

    a < -1, a == -1, a = 1, a > 1, b < -1, b == -1, b == 0, b == 1, b > 1
    c < -1, c == -1, c == 0, c == 1, c > 1.


    Input:
    Java Code:
    8
    -2	-2	-2	1
    -1	-1	-1	2
    1	-1	-1	1
    1	 0	 0     -1
    1	 1	 1     -2
    2	 2	 2	1
    1	 0	-4 	0
    1 	 0     -25 	1

    Skeleton:
    Java Code:
    /**
     * 
     */
    package cecs174;
    
    import java.io.File;
    import java.util.Scanner;
    import java.io.FileNotFoundException;
    
    
    /**
     * @author murgolo
     *
     */
    public class AssignmentFourMain 
    {
    	static final String FNAME = "ass4_input.txt";
    	/**
    	 * @param args
    	 */
    	public static void main(String[] args) 
    	{
    		Scanner inFile = null;
    
    		try
    		{
    			inFile = new Scanner(new File(FNAME));
    		}
    		catch(FileNotFoundException e)
    		{
    			System.out.println("Error: " + e.getMessage());
    			System.out.println("Make sure " + FNAME + " is in the project's top level directory");
    			System.exit(1);
    		}
    		 
    		int count = inFile.nextInt();
    		double checkSum = 0;
    		
    		for(int ii = 0; ii < count; ++ii)
    		{
    			int a = inFile.nextInt();
    			int b = inFile.nextInt();
    			int c = inFile.nextInt();
    			int x = inFile.nextInt();
    			
    			String poly = "";
    			// COMPLETE
    
    			System.out.println("Polynomial is " + poly);
    			
    			int discriminate ;
    			// COMPLETE
    			
    			System.out.println("The discriminate is " + discriminate);
    			
    			int numRealRoots = 0, numImagRoots = 0;
    			double root1 = 0.0, root2 = 0.0;
    			// COMPLETE
    			
    			System.out.println("Number of real roots = " + numRealRoots);
    			System.out.println("Number of imaginary roots = " + numImagRoots);
    			
    			System.out.print("Equation " + poly + " = 0 has ");
    	        	// COMPLETE
    	
    			System.out.println("The value of " + poly + " at " + x + " is: "); // COMPLETE
    			
    			checkSum += root1 + root2;
    			
    		}
    		
    		System.out.println("Check sum is " + checkSum);
    		inFile.close();
    		System.exit(0);
    	}
    
    }


    Desire output


    (a,b,c,x) = (-2,-2,-2,1)
    Polynomial is -2x^2 - 2x - 2
    The discriminate is -12
    Number of real roots = 0
    Number of imaginary roots = 2
    Equation -2x^2 - 2x - 2 = 0 has no real roots
    The value of -2x^2 - 2x - 2 at 1 is: -6

    (a,b,c,x) = (-1,-1,-1,2)
    Polynomial is -x^2 - x - 1
    The discriminate is -3
    Number of real roots = 0
    Number of imaginary roots = 2
    Equation -x^2 - x - 1 = 0 has no real roots
    The value of -x^2 - x - 1 at 2 is: -7

    (a,b,c,x) = (1,-1,-1,1)
    Polynomial is x^2 - x - 1
    The discriminate is 5
    Number of real roots = 2
    Number of imaginary roots = 0
    Equation x^2 - x - 1 = 0 has two real roots = (1.618033988749895,-0.6180339887498949)
    The value of x^2 - x - 1 at 1 is: -1

    (a,b,c,x) = (1,0,0,-1)
    Polynomial is x^2
    The discriminate is 0
    Number of real roots = 1
    Number of imaginary roots = 0
    Equation x^2 = 0 has one real root = 0.0
    The value of x^2 at -1 is: 1

    (a,b,c,x) = (1,1,1,-2)
    Polynomial is x^2 + x + 1
    The discriminate is -3
    Number of real roots = 0
    Number of imaginary roots = 2
    Equation x^2 + x + 1 = 0 has no real roots
    The value of x^2 + x + 1 at -2 is: 3

    (a,b,c,x) = (2,2,2,1)
    Polynomial is 2x^2 + 2x + 2
    The discriminate is -12
    Number of real roots = 0
    Number of imaginary roots = 2
    Equation 2x^2 + 2x + 2 = 0 has no real roots
    The value of 2x^2 + 2x + 2 at 1 is: 6

    (a,b,c,x) = (1,0,-4,0)
    Polynomial is x^2 - 4
    The discriminate is 16
    Number of real roots = 2
    Number of imaginary roots = 0
    Equation x^2 - 4 = 0 has two real roots = (2.0,-2.0)
    The value of x^2 - 4 at 0 is: -4

    (a,b,c,x) = (1,0,-25,1)
    Polynomial is x^2 - 25
    The discriminate is 100
    Number of real roots = 2
    Number of imaginary roots = 0
    Equation x^2 - 25 = 0 has two real roots = (5.0,-5.0)
    The value of x^2 - 25 at 1 is: -24
    Check sum is 1.0
    Last edited by Fubarable; 02-27-2011 at 02:23 AM.

  2. #2
    Fubarable's Avatar
    Fubarable is offline Moderator
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    Default

    Moderator edits:

    1) moved from Eclipse forum to the New To Java forum for closer forum-topic alignment.
    2) code tags added to help make code and data readable.

  3. #3
    juvenchan is offline Member
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    This is how far I go..
    I don't know how to write .... I am really stuck at this point.:(
    The following is the things I wrote.. and a printscreen (to let u see the errors):)


    /**
    *
    */
    package cecs174;

    /**
    * @author Juven
    *
    */
    public class AssignmentFour
    {
    static final String FNAME = "ass4_input.txt";

    /**
    * @param args
    */
    public static void main(String[] args)
    {
    Scanner inFile = null;

    try
    {
    inFile = new Scanner(new File(FNAME));
    }
    catch(FileNotFoundException e)
    {
    System.out.println("Error: " + e.getMessage());
    System.out.println("Make sure " + FNAME + " is in the project's top level directory");
    System.exit(1);
    }

    int count = inFile.nextInt();
    double checkSum = 0;

    for(int ii = 0; ii < count; ++ii)
    {
    int a = inFile.nextInt();
    int b = inFile.nextInt();
    int c = inFile.nextInt();
    int x = inFile.nextInt();

    String poly = "";
    // COMPLETE
    poly = poly + a + " x^2 " + " + " + b + " x " + " + " + c ;


    System.out.println("Polynomial is " + poly);


    int discriminate ;
    // COMPLETE
    discriminate = b * b - 4 * a * c;

    if ( discriminate < 0 );
    numRealRoots = 0;
    numImagRoots = 2;

    else if ( discriminate == 0 )
    numRealRoots = 1;
    numImagRoots = 0;

    else ( discriminate > 0 )
    numRealRoots = 2;
    numImagRoots = 0;
    System.out.println("The discriminate is " + discriminate);

    int numRealRoots = 0, numImagRoots = 0;
    double root1 = 0.0, root2 = 0.0;
    // COMPLETE

    System.out.println("Number of real roots = " + numRealRoots);
    System.out.println("Number of imaginary roots = " + numImagRoots);

    System.out.print("Equation " + poly + " = 0 has ");
    // COMPLETE
    double polyvalue;
    polyvalue = a * x * x + b * x + c ;

    System.out.println("The value of " + poly + " at " + x + " is: "); // COMPLETE

    checkSum += root1 + root2;

    }

    System.out.println("Check sum is " + check Sum);
    inFile.close();
    System.exit(0);
    }

    }



  4. #4
    pbrockway2 is offline Moderator
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    The usual way of doing things is to post the compiler messages if you can't understand them.

    In this case one source of error stands out straight away: use braces with every if and else block, even ones that are only one line long.

    Java Code:
    if(something) [b][color=red]{[/color][/b]
        // code
    [b][color=red]}[/color][/b] else if(somethingElse) [b][color=red]{[/color][/b]
        // code
    [b][color=red]}[/color][/b] else [b][color=red]{[/color][/b]
        // code
    [b][color=red]}[/color][/b]

  5. #5
    juvenchan is offline Member
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    oh.. braces for every if .. else if..
    i want to ask..
    where should i put my ass4_input.txt ??
    there are three errors around the scanner file.. how to I fix that.

    Thanks pbrockway

  6. #6
    juvenchan is offline Member
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    comparing the desire out put and my code..
    am I right to put numRealRoots and numImagRoots in that place?

  7. #7
    pbrockway2 is offline Moderator
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    Quote Originally Posted by juvenchan View Post
    oh.. braces for every if .. else if..
    i want to ask..
    where should i put my ass4_input.txt ??
    there are three errors around the scanner file.. how to I fix that.

    Thanks pbrockway
    You're welcome.

    Please post the compiler messages. I *think* you have not imported the Scanner class or the FileNotFoundException class, so the compiler will complain about that.

    One thing: when you post code use the "code" tags. Put [code] at the start of the code and [/code] at the end. That will preserve the formatting. Most people (including me!) are more inclined to read the code if it is properly formatted.

  8. #8
    juvenchan is offline Member
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    Quote Originally Posted by pbrockway2 View Post
    You're welcome.

    Please post the compiler messages. I *think* you have not imported the Scanner class or the FileNotFoundException class, so the compiler will complain about that.

    One thing: when you post code use the "code" tags. Put [code] at the start of the code and [/code] at the end. That will preserve the formatting. Most people (including me!) are more inclined to read the code if it is properly formatted.
    Exception in thread "main" java.lang.Error: Unresolved compilation problems:
    Scanner cannot be resolved to a type
    Scanner cannot be resolved to a type
    File cannot be resolved to a type
    FileNotFoundException cannot be resolved to a type
    numRealRoots cannot be resolved to a variable
    numImagRoots cannot be resolved to a variable
    numRealRoots cannot be resolved to a variable
    numImagRoots cannot be resolved to a variable
    Syntax error on token ")", } expected
    numRealRoots cannot be resolved to a variable
    numImagRoots cannot be resolved to a variable
    Syntax error on token "}", delete this token
    Syntax error, insert "}" to complete ClassBody

    at cecs174.AssignmentFour.main(AssignmentFour.java:19 )

    I don't get what u mean by using
    Java Code:
    put my codes here?
    sorry that I am a newbie in java or any programming

  9. #9
    pbrockway2 is offline Moderator
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    Did you understand what I meant by having to include Scanner and FileNotFoundException?

    Find out what package they belong to and put an import line for each just below the package statement at the top. (Check notes/textbook etc for examples of this.)

    numRealRoots cannot be resolved to a variable

    This means that you have not declared numRealRoots anywhere (you have to tell the compiler that it's an int). You need a line like

    Java Code:
    int numRealRoots;

    before you use that variable. You did that for discriminant and you have to do it for all variables.

  10. #10
    juvenchan is offline Member
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    after u see the desire output.
    how should I declare the numRealRoots and numImagRoots?
    do u mind give me a hand, or .. help me to write it?
    i don;t have the java book with me..
    oh boy.. java really makes me headache.. haha
    r u cs major?

  11. #11
    pbrockway2 is offline Moderator
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    I don't write code for people.

    As far as including the necessary imports and declaring variables before use is concerned (and that's a fair number of the compiler messages) your best bet is to consult some text or online tutorial. Oracle's Tutorial covers the basics in the section Learning the Java Language.

    Many other online tutorials exist - including one linked to here within the lat couple of days that looked very good.

  12. #12
    juvenchan is offline Member
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    oh..
    i think i wrong it in the wrong place..
    i replace it.. it shows no error..for that part..
    but the scanner still cannot be resolved...... interesting....

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