/**
  * 将所有的字节数组全部写入内存中，之后将其转化为字节数组
  */
  public static void main(String[] args) throws IOException {
    String str1 = "132";
    String str2 = "asd";
    ByteArrayOutputStream os = new ByteArrayOutputStream();
    os.write(str1.getBytes());
    os.write(str2.getBytes());
    byte[] byteArray = os.toByteArray();
    System.out.println(new String(byteArray));
  }

/**
  *  从内存中读取字节数组
  */
  public static void main(String[] args) throws IOException {
    String str1 = "132asd";
    byte[] b = new byte[3];
    ByteArrayInputStream in = new ByteArrayInputStream(str1.getBytes());
    in.read(b);
    System.out.println(new String(b));
    in.read(b);
    System.out.println(new String(b));
  }