How to prevent infinite loop when using Singleton pattern?

[KSBeyaz]

Guys how to prevent infinite loop when using singleton pattern?

here is my problems:(

import java.io.IOException;
import java.util.ArrayList;


public class Library implements CollectionAggregate {
	
	public ArrayList <Collection> aggregate =new ArrayList<Collection>() ;
	private FileReaderWriter file ;
	private static  Library instance;
	
	public LibraryIterator iterator=null;
	
	public Library(String preventLoop){
		
	}
	private Library() {
		System.out.println(k);
		
		try {
			
			file=new FileReaderWriter();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
		
	}
	
	
	public LibraryIterator iterator() {
		iterator=new LibraryCollectionIterator();
		return  iterator;
	}

	//degiscek....
	public ArrayList<Collection> getAggregate() {
		return aggregate;
	}


	public void addAggregate(Collection collection) {
		aggregate.add(collection);
		
	}
	public static Library getInstance() {
		if (instance==null)
			return instance=new Library();
		else	return instance;
	}
	
}

this the another class and it goes infinite loop

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.StringTokenizer;


public class FileReaderWriter {
	private PrintWriter writer;
	private BufferedReader reader;
	private String log;
	private Library library;
	
	
	
	FileReaderWriter()throws IOException {
		reader = new BufferedReader(new FileReader("c:\\LibraryData.txt"));
		readContent();
		//writer = new PrintWriter(new FileWriter("c:\\LibraryData.txt"),true);
		
		
	}
	public void readContent() throws IOException {
		
		String line="";
		while((line=reader.readLine())!=null){  
			String kayit=line;
			StringTokenizer token = new StringTokenizer(kayit);
			while(token.hasMoreTokens()){
				String type =token.nextToken();
				String name =token.nextToken();
				String auther =token.nextToken();
				String date =token.nextToken();
				System.out.println(date);
				int code =Integer.parseInt(token.nextToken());
				Collection collection = new Collection(type,name,auther,date,code);
				library=Library.getInstance();
				library.addAggregate(collection);
				
			}
			
		}
		

}

	
	/*public void printReport(String report) {
		
		 writer.println(report);
		 writer.flush();
	
				
			
	}*/
	
}

[Fubarable]

What line(s) are involved in your problem?

[Tolls]

If you show us the stack trace for the overflow exception we should be able to show you exactly where the problem lies.
As a start point, though, can you remove the public constructor for Library (Library(String)) and, for the 'instance' declaration do:

private static Library instance = new Library();

and then change the getInstance to:

public static Library getInstance() {
    return instance;
}

I can't guarantee this will cure the loop, since you haven't posted the stack trace, but it will make your singleton neater and less prone to having the constructor called multiple times, which would cause a problem.

[KSBeyaz]

What line(s) are involved in your problem?

the problem is that it goes infinite loop that i have checked with system.out.println(" b" ); it did write b infitly and program had not given a error msg.

so that i cant figure out where the problem occur :(