Prova così:
codice:
        BufferedReader br = null;
        try {
            br = new BufferedReader(new FileReader(file));
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
        boolean trovato=false;
        String riga=null;
        String codice="1";//codice da cercare
        try {
            riga = br.readLine();
        } catch (IOException ex) {
            ex.printStackTrace();
        }
        while(riga!=null){
            if(riga.startsWith(codice)){   //controllo
                System.out.println("Risultato="+riga);
                trovato=true;
            }
            try {
                    riga = br.readLine();
                } catch (IOException ex) {
                    ex.printStackTrace();
                }
        }
        if(!trovato)
            System.out.println("Nessun riscontro");