import java.util.Iterator;
import java.util.NoSuchElementException;
import java.io.BufferedReader;
import java.io.IOException;

public class LineIterator implements Iterator<String> {
	
	public static final Iterable<String> lines(final BufferedReader in) {
		return new Iterable<String>() {
			private BufferedReader in_ = in;
			
			public Iterator<String> iterator() {
				if (in_ == null) throw new IllegalStateException("iterator cannot be called more than once");
				Iterator<String> it = new LineIterator(in_);
				in_ = null;
				return it;
			}
		};
	}
	
	private final BufferedReader in;
	private String next;
	
	public LineIterator(BufferedReader in) {
		this.in = in;
		advance();
	}
	
	private void advance() {
		try {
			next = in.readLine();
		}
		catch (IOException e) {
			next = null;
		}
	}
	
	public String next() {
		if (!hasNext()) throw new NoSuchElementException();
		String next = this.next;
		advance();
		return next;
	}
	
	public boolean hasNext() {
		return next != null;
	}
	
	public void remove() {
		throw new UnsupportedOperationException();
	}
	
}