This quiz asks you to complete the two methods described below. Each item to be

Question

This quiz asks you to complete the two methods described below. Each item to be filled in is marked by ?n?. Question n asks you to fill in ?n?. The grepScanner method should read one line at a time from the Scanner object and return all the lines that contain the pattern as a substring. The grepFile method should call the above grepScanner method using a Scanner created from the File object. However, two runtime errors should be handled. If the file is not found, then this method should return an empty ArrayList. If file and/or pattern is null, then this method should return null. This method should not handle any other runtime errors.

Explanation / Answer

I have written the code for the second grepfile function in java using regex from library. Code is :

public static ArrayList grepFile(File file,String pattern)

{

Matcher matcher = pattern.matcher("");
  
try
{
input_read = new BufferedReader(new FileReader(file));
}
catch (IOException e)
{
System.err.println("Unable to read the line '" + file + "': " + e.getMessage());
}
while ((line = input_read.readLine()) != null)
{
matcher.reset(line);
if (matcher.find())
{
System.out.println(file + " contains this : " + line);
}
}
input_read.close();

}

I am handing the exception with the try catch block as mentioned in the problem statement.

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