doubt about string replacement

[Anonymous]

Hi friends!
i got a problem with strings.
i want to read a line from a file and replace a part of the line with new string.i want to compare whether the old string exists in the line or not and if exists i have to replace with the new string.i can not predict that there can be spaces in the line.
can any body help in solving the problem.
thanks
kiran

[Apu Nahasapeemapetilon]

Pretty easy, I think. What do we do when we don't find string to be replaced?
line = line read from file
oldstr = string to be replace
newstr = string to replace oldstr
result = line with oldstr replaced with newstr
//first does old string exist
int pos;
pos = line.indexOf (oldstr);
if (pos > 0) //we found it
{
result = line.substring (0, pos) + newstr + line.substring ( pos + oldstr.length()) ;
}
else //we didn't find it
{
//now what???
result = line;
}
return result;

[Serge Plourde]

Hi, bkkumar!
This may be more than want you needed. But I found it chalenging to do, so maybe just keep what you need.
I called it SNR (Search and Replace).
<code>
import java.io.*;
import java.util.*;
public class SNR
{
public static void main(String[] args) throws IOException
{
System.out.println("Your file: " + args[0]);
System.out.println("...will have its string(s): " + args[1]);
System.out.println("...replaced with : " + args[2]);
BufferedReader in = new BufferedReader( new FileReader(args[0]) );
String newText = new String();
String line;
StringTokenizer st;
String token;

while ( (line = in.readLine()) != null )
{
st = new StringTokenizer(line, " ,.-?!", true);
while (st.hasMoreTokens())
{
token = st.nextToken();
newText += (token.equals(args[1]) ? args[2] : token);
}
newText+="\n";
}
in.close();
BufferedReader inNewText =
new BufferedReader( new StringReader(newText) );
PrintWriter out =
new PrintWriter( new BufferedWriter( new FileWriter( args[0] ) ) );
while ( (line = inNewText.readLine()) != null) out.println(line);
out.close();
}
}
</code>
Of course you'll have to catch possible exceptions and make sure that the arguments are in proper number, etc...