indexOf implementation in Java

[Vatsa dude]

Hi,
This is for my wife who's a newbie in java. Can anyone please help? I am looking for the java method fully implemented..

"Problem:
Implement the strstr from string.h in the C standard library. This function is also know as index in Perl, and indexOf in Java and JavaScript.
The function should take two string parameters, short and long (note that these are just the variable names, not types), and return the first occurrence of short in long as a 0 based index into long. If short does not exist in long, the function should return -1.
You should provide a suite of test data along with your implementation.
Example: if str1=”cap”, str2=”escape”, applying strstr(str1,str2) should return 2

Constraints
You can use Java or C but MUST NOT use high level language facilities such as regular expressions or multi-character string comparisons.
If you choose to implement in C, you may return a char * that points to the character from long where the match begins, or NULL if short is not found.
This should be written as "production quality" code, meaning that it should be code you'd be willing to check in to a production tree. No extraneous debug statements, exit() calls, or anything else that would disturb production code.
The solution should be expressed in a single file with no outside dependencies. It should contain at least one function named strstr that performs the task, and one function named test that returns a true value if the strstr function passes all testcases. You may factor strstr into multiple functions if you like.
"

[Christophe Verré]

Welcome to the ranch !
Please read this first.

[Joanne Neal]

The function should take two string parameters, short and long (note that these are just the variable names, not types),

It's not possible to implement this part of the requirement in Java

[Vatsa dude]

Hi Joanne,
Why is that? I know out of the box indexOf() method does not have a (string,string) signature. Any specific reason why you think it can't be done?

Thanks
Sri

[Henry Wong]

Sri Vatsa wrote:Hi Joanne,
Why is that? I know out of the box indexOf() method does not have a (string,string) signature. Any specific reason why you think it can't be done?

Thanks
Sri

"short" and "long" are reserved words in Java -- you can't have parameters with those names.

Henry

[Vatsa dude]

Oh that, I think that's merely an example - probably intended to put off the programmer. Except that constraint, it can be done - right? I will try to do it tonight after work..

[Henry Wong]

BTW, you do understand that you are not allowed to use the Java indexOf() method for this homework problem, right? If you do, you are violating this constraint.

You can use Java or C but MUST NOT use high level language facilities such as regular expressions or multi-character string comparisons.

The indexOf() method does a multi-character string comparision to find that index.

Henry

[Vatsa dude]

Yes, I understand. Its my wife's homework - I am trying to help her out..

[Vatsa dude]

Hi Henry,
I think I am allowed to a character by character comparison in a nested for loop.

I don't think this qualifies a multi-character comparison, right. I am thinking of having 2 for loops and using break(); once a match is found (Note that I can't use any exit() calls).

Thanks
Sri

[Henry Wong]

Sounds good.

Henry

[Campbell Ritchie]

Not break() but break. Another reserved word.

[Vatsa dude]

Hi,
I have the basic body of StringTest working. Can you please help me modularize the program with test() functionality. I am referring to this particular requirement "The solution should be expressed in a single file with no outside dependencies. It should contain at least one function named strstr that performs the task, and one function named test that returns a true value if the strstr function passes all testcases."

I cannot use properties file for loading the test data since external dependecy is not allowed. Any hints?

  
public class StringTest{

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		String src =  "cap";
		String dest = "escapercap";
		
		int result = stringSearch(dest,src);
		System.out.println("Result == "+result);
		
	}
    public static  int stringSearch(String baseStr, String compareStr){
        if((baseStr==null) ||(compareStr==null)){
            return -1;
        }
        
      int baseLength = baseStr.length();
        int compareLength =compareStr.length();
        char baseStrCharArray[] = baseStr.toCharArray();
        char compareStrCharArray[] =compareStr.toCharArray();
        
        if(compareLength > baseLength){
            return -1;
        }
        int startIndex=0,endIndex;
        
        for(int i=0;i < baseLength;i++){
                if(baseStrCharArray[i]== compareStrCharArray[0]){
                      startIndex=endIndex=i++;
                      for(int j=1;(j<compareLength)&&(i<baseLength);j++,i++){
                            if(baseStrCharArray[i]== compareStrCharArray[j])
                                  endIndex=i;
                            else
                                  break;                            
                      }
                      //System.out.println("Start Index " + startIndex);
                      //System.out.println("End Index " + endIndex);
                      
                      if(((endIndex+1)-startIndex)==compareLength){
                            System.out.println("Match found");
                            return startIndex;
                      }
                      i=startIndex;
                }
        }
        return -1;
 }

}
  

[Balu Sadhasivam]

I cannot use properties file for loading the test data since external dependecy is not allowed. Any hints?

Sri,

Use java command line arguments to load data. If you dont need it anytime , you can check for null and assign your own value in the code.