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Thread: Working with Methods

  1. #1
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    Default Working with Methods

    This is my code:

    import javax.swing.JOptionPane ;
    import java.util.Date ;
     
     
    public class blahblah  {
      // *************************************************************************main
      public static void main(String[] args) {
     
    	String province ;
     
    	province = getGoodProvinceCode() ;
     
    	}// close main
     
     
     
          // *********************************************************************getPST
      public static String getPST(String province) {
     
    	final double GST = 0.05 ;
    	final double AB_PST = 0.0  ; // AB provincial sales tax
    	final double BC_PST = 0.07 ; // BC provincial sales tax
    	final double MB_PST = 0.07 ; // MB provincial sales tax
    	final double NB_PST = 0.08 ; // NB provincial sales tax
    	final double NL_PST = 0.08 ; // NL provincial sales tax
    	final double NS_PST = 0.08 ; // NS provincial sales tax
    	final double ON_PST = 0.08 ; // ON provincial sales tax
    	final double PE_PST = 0.10 ; // PE provincial sales tax
    	final double QC_PST = 0.075 ; // QC provincial sales tax
        final double SK_PST = 0.05 ; // SK provincial sales tax
    	double pst ;
    	double gst ;
    	double hst ;
     
    	String prov ;
     
    	province = getGoodProvinceCode() ;
     
    	// find tax rates
        gst = GST ;
        hst = pst = 0. ;
        if ( province.equals("AB") )
          pst = 0. ;
        else if ( province.equals("BC") )
          pst = BC_PST;
        else if ( province.equals("MB") )
          pst = MB_PST;
        else if ( province.equals("NB") ) {
          pst = gst = 0;
          hst = GST + NB_PST ;
        }
        else if ( province.equals("NL") ) {
          pst = gst = 0;
          hst = GST + NL_PST ;
        }
        else if ( province.equals("NS") ) {
          pst = gst = 0;
          hst = GST + NS_PST ;
        }
        else if ( province.equals("ON") )
          pst = ON_PST;
        else if ( province.equals("PE") )
          pst = PE_PST;
        else if ( province.equals("QC") )
          pst = QC_PST;
        else if ( province.equals("SK") )
          pst = SK_PST;
        else
          pst = -1 ;
     
        if ( hst > 0 ) {
    		prov = ("H" + hst) ;
    	}
    	else if ( hst == 0 ) {
    		prov = ("P" + pst) ;
    	}
    	else {
    		prov = ("") ;
    	}
     
    	return prov ;
     
      }// close getPST
     
          // *********************************************************************getGoodProvinceCode
      public static String getGoodProvinceCode() {
     
    	  String prompt ;
    	  String errorMsg ;
    	  String provinceC = "" ;
    	  String prov ;
    	  String province = "" ;
     
    	  boolean inputOk ;
     
        // input province
        prompt = "Enter two-letter province abbreviation (e.g., MB)" ;
        inputOk = false ;
        errorMsg = "" ;
        prov = getPST(province) ;
        while ( ! inputOk ) {
          provinceC = JOptionPane.showInputDialog(null, errorMsg + prompt) ;
          provinceC = provinceC.toUpperCase().trim() ;
          if ( prov.equals("") ) {
            errorMsg = "Input " + provinceC
              + " is not a valid province abbreviation\n" ;
            System.out.println( errorMsg ) ;
    	  }
          else {
            inputOk = true ;
          }
        }
     
        return provinceC ;
     
      }// close getGoodProvinceCode
     
    }// close class

    I get this error:

    Exception in thread "main" java.lang.StackOverflowError
    	at ChurchAustinA3Q1.getGoodProvinceCode(ChurchAustinA3Q1.java:101)
    	at ChurchAustinA3Q1.getPST(ChurchAustinA3Q1.java:48)
    	at ChurchAustinA3Q1.getGoodProvinceCode(ChurchAustinA3Q1.java:111)
    	at ChurchAustinA3Q1.getPST(ChurchAustinA3Q1.java:48)
    	at ChurchAustinA3Q1.getGoodProvinceCode(ChurchAustinA3Q1.java:111)
    	...etc...

    I think I am getting an error because getGoodProvinceCode() calls getPST(String province), and then getPST(String province) calls getGoodProvinceCode(). I just don't know how to fix this loop.

    EDIT/ Is it possible to return a variable in the middle of a method without ending the method at that point?
    Last edited by duckman; November 8th, 2009 at 04:55 PM.


  2. #2
    Super Moderator helloworld922's Avatar
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    Default Re: Working with Methods

    What you essentially have is a malformed recursive function.

    To fix:

    Have your main method call getProvince() to get a province, then call getPST() to get the sales tax rate for that province. Remove all calls from getProvince() to getPST() and vise-versa. You'll also need to adjust your methods to not call each other.

    No, a method may not return a value and continue running. That would violate the method contract.

  3. The Following User Says Thank You to helloworld922 For This Useful Post:

    duckman (November 9th, 2009)

  4. #3
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    Default Re: Working with Methods

    in the while loop of getGoodProvinceCode() u didnt tell the while loop how to break if 'prov= "" '. Hence it continues running that loop which resulted into the stackoverflow error.
    The solution is to place just a 'break statement' after printing 'errorMsg' and your problem is solved.

  5. The Following User Says Thank You to oyekunmi For This Useful Post:

    duckman (November 9th, 2009)

  6. #4
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    Default Re: Working with Methods

    Thank you helloworld922 and oyekunmi, I figured it out now.

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