code: @Test public void writeReadStringTest() throws IOException {
    ByteArrayOutputStream os=new ByteArrayOutputStream();
    DataOutputStream dos=new DataOutputStream(os);
    List<String> strings=new ArrayList<String>();
    strings.add("");
    strings.add(null);
    strings.add("abc xyz");
    strings.add("123 789");
    strings.add("!@#$%^&*()_+}{\":?><");
    for (int k=0; k < strings.size(); k++) {
      Utils.writeString(strings.get(k),dos);
    }
    DataInputStream dis=new DataInputStream(new ByteArrayInputStream(os.toByteArray()));
    for (int k=0; k < strings.size(); k++) {
      Assert.assertEquals(strings.get(k),Utils.readString(dis));
    }
    dos.close();
    dis.close();
  }
  