java exercise help

Find the 10 most common and 10 least common words in the textfile.
Find the 10 most common and 10 least common bigrams in the file. (A bigram is two words following each other in the text. (F.ex. "The red fox" contains 2 bigrams: "The red" and "red fox". - See http://en.wikipedia.org/wiki/Bigram) )
Find the longest phrase that also appears at least twice.
("longest phrase" here means the number of words, NOT letters)

Please tell us what you have done so far. Please tell us *exactly* what issue you are running into. We can't help you if we don't know where you are stuck.

Henry

The issue i am facing is for correct regexp

i am getting words as citizen. citzen, and citizen; i want to remove the , . ; after words and then check for thier repetition in file .

import javax.swing.filechooser.FileNameExtensionFilter;

/**
 * @author 
 *
 */
public class StandAlone {

/**
	 * 
	 */
	public StandAlone() {
		// TODO Auto-generated constructor stub
	}

public static void main(String[] args) 
    {
        Map<String, Integer> unique = new LinkedHashMap<String, Integer>();
        Scanner aScanner = selectTextFile();
        while(aScanner.hasNext())
        {
        	System.out.println(aScanner.next());
        }

}

public static String join(Collection<String> s, String delimiter) {
        StringBuffer buffer = new StringBuffer();
        Iterator<String> iter = s.iterator();
        while (iter.hasNext()) {
            buffer.append(iter.next());
            if (iter.hasNext()) {
                buffer.append(delimiter);
            }
        }
        return buffer.toString();
    }
    
    
    public static Scanner selectTextFile(){
    	do{
    		JFileChooser chooser = new JFileChooser();
    		FileNameExtensionFilter afilter = new FileNameExtensionFilter("Text files","txt");
    		chooser.setFileFilter(afilter);
    		int returnVal = chooser.showOpenDialog(null);
    		
    		try
    		{
    			if(returnVal == JFileChooser.APPROVE_OPTION)
    			{
    				return new Scanner(chooser.getSelectedFile());
    			}
    			else
    			{
    				return null;
    			}
    		}
    		catch(FileNotFoundException ef)
    		{
    			JOptionPane.showMessageDialog(null, "Invalid File!","error",JOptionPane.ERROR_MESSAGE);
    		}
    				
    		}
    	while(true);
    
    }

}

Please UseCodeTags next time. I've added them for you this time.

Welcome to the Ranch

I do not think a regular expression will help you at all. Go through the Java™ Tutorials Collections section and you will find a counting application example.