Write a program to read several lines from a file called H.in. For each line, ch

ID: 3864337 • Letter: W

Question

Write a program to read several lines from a file called H.in. For each line, check whether it is a palindrome. For each line read from the file, print only the lines that are palindromes. Recall that a palindrome is a string that is the same backwards and forwards, ignoring spaces and punctuation. Some example palindromes are “radar” and “I, Madam, I made radio. So I dared! Am I mad? Am I??” You may use theremoveWS method from Lab. Your palindrome checking method must be recursive. In JAVA:

removeWS :

public static String removeWS(String a)
{
if (a.length() == 0)
return a;

String b = Character.isLetterOrDigit(a.substring(0, 1).charAt(0)) ? a.substring(0, 1) : "";
return b + removeWS(a.substring(1));
}
}

H.in:

You must be the change you want to see in the world
Sore was I, ere I saw Eros.
A man, a plan, a canal -- Panama
Never a foot too far, even.
BORROW - OR ROB?
Euston SaW I was not Sue.
THIS IS JUST A TEST.
"Stop!" nine myriad murmur. "Put up rum, rum, dairymen, in pots."
Live on evasions?! No, I save no evil.
Red Roses run no risk, sir, on nurses order.
The best way out is always through........

Explanation / Answer

// PalindromeRecursion.java
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.File;

public class PalindromeRecursion
{
   public static String removeWS(String a)
   {
   if (a.length() == 0)
           return a;

   String b = Character.isLetterOrDigit(a.substring(0, 1).charAt(0)) ? a.substring(0, 1) : "";
       return b + removeWS(a.substring(1));
   }

   // check palindrome
   public static boolean isPalindrome(String s)
   {
       if(s.length() == 0 || s.length() == 1)
return true;
if(s.charAt(0) == s.charAt(s.length()-1))
   return isPalindrome(s.substring(1, s.length()-1));
return false;
   }

   // method o read file
   public static void readFile() throws IOException
   {
       File file = new File("H.in");

       FileInputStream fileStream = new FileInputStream(file);

       BufferedReader bufferRead = new BufferedReader(new InputStreamReader(fileStream));

       String line = null;
       String s = null;
       while ((line = bufferRead.readLine()) != null)
       {
           s = removeWS(line);
           s = s.toLowerCase();
           if(isPalindrome(s) == true)
               System.out.println(line);
       }

       bufferRead.close();
   }

public static void main(String[] args)
{

       try
       {
       readFile();
       }
       catch(IOException e)
       {
       e.printStackTrace();
       }
   }
}

/*
output:
Sore was I, ere I saw Eros.
A man, a plan, a canal -- Panama
Never a foot too far, even.
BORROW - OR ROB?
Euston SaW I was not Sue.
"Stop!" nine myriad murmur. "Put up rum, rum, dairymen, in pots."
Live on evasions?! No, I save no evil.
Red Roses run no risk, sir, on nurses order.

H.in
You must be the change you want to see in the world
Sore was I, ere I saw Eros.
A man, a plan, a canal -- Panama
Never a foot too far, even.
BORROW - OR ROB?
Euston SaW I was not Sue.
THIS IS JUST A TEST.
"Stop!" nine myriad murmur. "Put up rum, rum, dairymen, in pots."
Live on evasions?! No, I save no evil.
Red Roses run no risk, sir, on nurses order.
The best way out is always through........

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