.append() method

[Bryan Peach]

Hey,
I am trying to write this method that gets rid of all the whitespace and punctuation in a statement. I try to use the .append() method but when I go to compile I get a "Cannot find symbol method append(char)" error. Here is the code for my method. Can anyone see why I am getting this error? Thanks.

    
public static String stripPunct(String s)
    {
    	String outstring;
    	
    	for(int i=0;i<s.length();i++)
    	{
    		char c= s.charAt(i);
    		if((c>='A'&&c<='Z')||(c>='a'&&c<='z'))
    		{
    			outstring.append(c);
    			return outstring;
    		}
    	}	
    }

[Patel Chintan]

Hi,
you are using 'outstring' variable of String class, and String class doesn't have append method. You should use StringBuilder or StringBuffer class.

[Siva Masilamani]

String has concat not append method

[Bryan Peach]

Ok well when I try to use the StringBuffer class I get a bunch of incompatible type errors, and when i try to use the .concat method it gives me an error saying that I cannot use that method to add a char to a string... Something so simple seems so confusing right now.... Here is my entire code.. It might make it easier to spot what is going on... Thanks for the help..

    
import java.util.ArrayList; 
import java.io.*; 
import java.util.Scanner; 
public class Palindrome {
	String p;
	
	public static ArrayList<String> list1;	//declaring a list called list1
	
	public static void createList()	//method that reads from file and creates list 
    {
    	FileReader inFileReader;
    	try {		//try catch statement to catch a file not found exception
    		 inFileReader = new FileReader("PalindromeInput.txt");// initializing the File Reader object
    	
    	Scanner inFile = new Scanner(inFileReader);// creating a new file reader object
    	
    	while(inFile.hasNext())// loop that checks to see if inFile has another line
    	 	{
    	 		String s=inFile.nextLine();//creates a new Palindrome 
    	 		s=stripPunct(s);
    	 		list1.add(s.toLowerCase());// adds Palindrome s to the list list1
    	 	}
    	 	} catch(FileNotFoundException e)
    	{
    	
    	}	
    }
    
    public static boolean isPal(String p)
    {
    	if (p.length()==1)
    		return true;
    	else if (p.length()==2)
    	{
    		if(p.charAt(0)==p.charAt(1))
    			return true;
    	}
    	else if(p.charAt(0)==p.charAt(p.length()-1))
    	{
    		if(isPal(p.substring(1,p.length()-2)))
    			return true;
    	}
    	return false;	
    }
    
    public static String stripPunct(String s)
    {
    	String outstring;
    	
    	for(int i=0;i<s.length();i++)
    	{
    		char c= s.charAt(i);
    		if((c>='A'&&c<='Z')||(c>='a'&&c<='z'))
    		{
    			outstring.concat(c);
    			return outstring;
    		}
    	}	
    }
    
    public static void main(String[] args) throws IOException {
    	list1=new ArrayList<String>();//instantiating the list1 list
    	createList();//method call to create list
    	
    	for(int i=0;i<list1.size();i++)
    	{
    		String out=list1.get(i);
    		if(isPal(out))
    			System.out.println(out+ " is a palindrome.");
    		else
    			System.out.println(out + " is not a palindrome.");
    	}
    	
    	
    	
    }
}

[Siva Masilamani]

OK you should read API

concat method takes only String not char.

so use concat(Character.toString(c)) and you should be all set

[Bryan Peach]

That seems to have worked... Thank you.. But now it is saying that I may not have initialized the variable outstring... Any idea whats going on with that?

[Bryan Peach]

ok forget that last post... stupid me.. i figured it out... but now when i compile i get this error message.

Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 0
at java.lang.String.charAt(String.java:686)
at Palindrome.isPal(Palindrome.java:47)
at Palindrome.main(Palindrome.java:78)

Any ideas?

[Siva Masilamani]

If you are declaring variable inside a method or block it is called local variable.

All the instance or class level variables are initialized to default value but not the local variable not even to null if that local variable is reference type.

So you should initialize it befire you use that variable.

So it should be String outString=null;