Java - Palindrom

zk0 · 12-12-2006, 05:25 AM

I need some help with this Java code. It's supposed to be a code that says if a text is a palindrom or not (I have no idea what's its called in english). A palindrom is a text that will be spelled the same if it's read backwards (=adolf i paris rapar sirap i floda).

This is the start code:

Code:

package your_username;

public class Step3_Lab02
{
	public static void main(String[] args)
	{
	}
}

class Palindrome
{
	public boolean isPalindrome(String str)
	{
		String reverseStr = (new StringBuffer(str)).reverse().toString();
		return str.equalsIgnoreCase(reverseStr);
	}

	public String removeNoneLetters(String str)
	{
		String result = "";
		for (int i = 0; i < str.length(); ++i)
		{
			if (Character.isLetter(str.charAt(i)))
			{
				result = result + str.charAt(i);
			}
		}

		return result;
	}
}

I am only allowed to add new code in the main-method:

Code:

	public static void main(String[] args)
	{
	}

I've already added a Scanner to the code. It now loks like this:

Code:

package your_username;

import java.util.Scanner;

public class Step3_lab02
{

}

class Palindrome
{
	public boolean isPalindrome(String str)
	{
		String reverseStr = (new StringBuffer(str)).reverse().toString();
		return str.equalsIgnoreCase(reverseStr);
	}

	public String removeNoneLetters(String str)
	{
		String result = "";
		for (int i = 0; i < str.length(); ++i)
		{
			if (Character.isLetter(str.charAt(i)))
			{
				result = result + str.charAt(i);
			}
		}
		return result;
	}
}

If you think you can help me please post!

????: NamePros.com http://www.namepros.com/programming/268148-java-palindrom.html

I have problem with knowing how to delete all the signs that is not letters in the text I write.

And Im a little unsure how to use the method "nextLine" in the Scanner-class.

mr_love_monkey · 12-15-2006, 05:43 PM

Why do you need to use 'Scanner' - how are you planning on using this program?

Are you just going to give it a possible palindrome at the command line?

Surely all you would need to do in your main is

Code:

public static void main(String [] args) {
Palindrome p = new Palindrome();
String possiblePal = args[0];
possiblePal = p.removeNoneLetters(possiblePal);
if(p.isPalindrome(possiblePal))
   System.out.println("Is palindrome");
else
   System.out.println("Is not palindrome");
}

which expects your possible palindrome to be the first argument when you call the code

legend2 · 12-17-2006, 09:18 AM

Well think of it logically.
take the text from command line, through args[].

Then, start 2 indexed, one at 0 and one equal to the length of the string.
The first index moves forward, the second one backward.
Keeping incrementing the first and decrementing the second as long as the characters match at both indexes. yous top when 2 characters are not the same, or when the 2 pointers reach the same index or the first bypasses the second.

12-12-2006, 05:25 AM	THREAD STARTER #1 (permalink)
zk0 NamePros Member Join Date: Jun 2005 Posts: 163	Java - Palindrom I need some help with this Java code. It's supposed to be a code that says if a text is a palindrom or not (I have no idea what's its called in english). A palindrom is a text that will be spelled the same if it's read backwards (=adolf i paris rapar sirap i floda). This is the start code: Code: package your_username; public class Step3_Lab02 { public static void main(String[] args) { } } class Palindrome { public boolean isPalindrome(String str) { String reverseStr = (new StringBuffer(str)).reverse().toString(); return str.equalsIgnoreCase(reverseStr); } public String removeNoneLetters(String str) { String result = ""; for (int i = 0; i < str.length(); ++i) { if (Character.isLetter(str.charAt(i))) { result = result + str.charAt(i); } } return result; } } I am only allowed to add new code in the main-method: Code: public static void main(String[] args) { } I've already added a Scanner to the code. It now loks like this: Code: package your_username; import java.util.Scanner; public class Step3_lab02 { } class Palindrome { public boolean isPalindrome(String str) { String reverseStr = (new StringBuffer(str)).reverse().toString(); return str.equalsIgnoreCase(reverseStr); } public String removeNoneLetters(String str) { String result = ""; for (int i = 0; i < str.length(); ++i) { if (Character.isLetter(str.charAt(i))) { result = result + str.charAt(i); } } return result; } } If you think you can help me please post! ????: NamePros.com http://www.namepros.com/programming/268148-java-palindrom.html I have problem with knowing how to delete all the signs that is not letters in the text I write. And Im a little unsure how to use the method "nextLine" in the Scanner-class. __________________ Green Blog and Green Web Hosts. AdBrite Forum and Webmasters Blog.

12-15-2006, 05:43 PM	#2 (permalink)
mr_love_monkey NamePros Member Join Date: Oct 2004 Posts: 40	Why do you need to use 'Scanner' - how are you planning on using this program? Are you just going to give it a possible palindrome at the command line? Surely all you would need to do in your main is Code: public static void main(String [] args) { Palindrome p = new Palindrome(); String possiblePal = args[0]; possiblePal = p.removeNoneLetters(possiblePal); if(p.isPalindrome(possiblePal)) System.out.println("Is palindrome"); else System.out.println("Is not palindrome"); } which expects your possible palindrome to be the first argument when you call the code __________________ Cheap Domain Name Registration Cheap Web Hosting

12-17-2006, 09:18 AM	#3 (permalink)
legend2 Senior Member Join Date: Sep 2005 Posts: 1,112	Well think of it logically. take the text from command line, through args[]. Then, start 2 indexed, one at 0 and one equal to the length of the string. The first index moves forward, the second one backward. Keeping incrementing the first and decrementing the second as long as the characters match at both indexes. yous top when 2 characters are not the same, or when the 2 pointers reach the same index or the first bypasses the second.

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