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Message:

Recursive Strings (or rather strangulation)

Posted by Ken Wunderlich on October 21, 2001 at 8:42 PM

I'm a first year student and this program is required. I have some issues with the boolean return logic but I'm stuck. The requirement is to capture a string (keyboard input which is fine) and test to see if:

a) The string begins with either an x or x with an indefinite # of y's.
b) followed by a qz or qd.
c) followed by either an x or xyyyyyy.....
Take a look:
-----------------------------------------------------------
boolean analysis (int left, int right , String str)//blurb
{ foundX = false;
right = str.length();
str = str.toLowerCase();
if(left <= str.length())
{
//if(str.startsWith("x"))
if(index < str.length()&& str.startsWith("x")) //replace above
{foundX = true;

recognizeY(str,left+1);
recognizeQ(str,left+1);

return foundQ;}
else{System.out.println("x: " + false);
return foundX;}

}
System.out.println("Something not found: " + true);
return foundX;
}

boolean recognizeY(String str, int index)//Whooszit
{

if(index < str.length())//removed =
if (str.charAt(index) == 'y')
{foundY= true; //str = str.substring(0);

recognizeY(str, index+1);
System.out.println("foundY1: " + foundY);
return foundY;}

//str = str.substring(0);//changed 1 to 0

System.out.println("foundY2: " + foundY);
return foundY;}

boolean recognizeQ(String str, int index)//Whatszit
{

System.out.println("str: "+str);
System.out.println("index: "+index);
// index++;
// foundQ = false;
if (str.charAt(index) == 'q'&&foundY == true)
//str = str.substring(1); //new change
{foundQ=false;//changed true to false
System.out.println("str: "+str+" index: "+ index+" foundQ: "+foundQ);
recognizeQ(str,index);
return foundQ;}

if(str.charAt(index) == 'd' || str.charAt(index) == 'z')
{str = str.substring(1);
return foundQ = true;}
else
{// return foundQ;
// else
// {foundQ = true;
System.out.println("foundQ2: "+foundQ);
return foundQ;}//added new
}

----------------------------------------------------------
> Ack! This forum needs a preview before post!
> Here are the unadorned urls, since I will probably make another typo in correcting the original:
>

> J2SE 1.4:    http://java.sun.com/j2se/
> Jython:      http://www.jython.org/
> Third Party: http://industry.java.sun.com/solutions/?frontpage-main
> 

> - mfg
>

• J2SE 1.4 will have them in util.regex, but that is not yet released. You can download or find more details on the beta on Sun's website (above link).
• If you don't want to use a beta you could use Jython, which is Python running on Java.
  > >
• Finally, there are third party tools for Java that do regular expressions; go to Sun's Solution Marketplace and search for "regular expression."

  > > - mfg

  > > > How do you successfully identify patterns in a string using recursive methods. Let's say I want to identify a pattern of
  > > > x or xy...(+)qz or qd (+) x?

  > > > I appreciate any help you can provide.
  > > > K

  
  
  
  

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