JavaIO - Não encontra arquivo dentro do pacote

public class Principal {
	public static void main(String[] args) throws IOException {
		//InputStream is = System.in;
		InputStream is = new FileInputStream("/principal/arquivo.txt");
		InputStreamReader isr = new InputStreamReader(is);
		BufferedReader br = new BufferedReader(isr);
		
		String s = br.readLine();
		
		while (s != null) {
			System.out.println(s);
			s = br.readLine();
		}
	}