四、实例分析
同API一起下载的还有一个examples文件，里面有个最简单的读、写程序，对其进行注释，以增进了理。
（1）读串口
| 1 | import java.io.*; |
| 2 | import java.util.*; |
| 3 | import javax.comm.*; |
| 4 | |
| 5 | public class SimpleRead implements Runnable, SerialPortEventListener { |
| 6 | |
| 7 | static CommPortIdentifier portId; |
| 8 | static Enumeration portList;//枚举类 |
| 9 | |
| 10 | InputStream inputStream; |
| 11 | SerialPort serialPort; |
| 12 | Thread readThread; |
| 13 | |
| 14 | public static void main(String[] args) { |
| 15 | |
| 16 | portList = CommPortIdentifier.getPortIdentifiers();/*不带参数的getPortIdentifiers方法获得一个枚举对象，该对象又包含了系统中管理每个端口的CommPortIdentifier对象。注意这里的端口不仅仅是指串口，也包括并口。这个方法还可以带参数。getPortIdentifiers(CommPort)获得与已经被应用程序打开的端口相对应的CommPortIdentifier对象。 getPortIdentifier(String portName)获取指定端口名（比如“COM1”）的CommPortIdentifier对象。*/ |
| 17 | |
| 18 | while (portList.hasMoreElements()) { |
| 19 | portId = (CommPortIdentifier) portList.nextElement(); |
| 20 | if (portId.getPortType() == CommPortIdentifier.PORT_SERIAL)/*getPortType方法返回端口类型*/ { |
| 21 | // if (portId.getName().equals("COM1"))/* 找Windows下的第一个串口*/ { |
| 22 | if (portId.getName().equals("/dev/term/a"))/*找Unix-like系统下的第一个串口*/ { |
| 23 | SimpleRead reader = new SimpleRead(); |
| 24 | } |
| 25 | } |
| 26 | } |
| 27 | } |
| 28 | |
| 29 | public SimpleRead() { |
| 30 | try { |
| 31 | serialPort = (SerialPort) portId.open("SimpleReadApp", 2000);/* open方法打开通讯端口，获得一个CommPort对象。它使程序独占端口。如果端口正被其他应用程序占用，将使用 CommPortOwnershipListener事件机制，传递一个PORT_OWNERSHIP_REQUESTED事件。每个端口都关联一个 InputStream 何一个OutputStream。如果端口是用open方法打开的，那么任何的getInputStream都将返回相同的数据流对象，除非有close 被调用。有两个参数，第一个为应用程序名；第二个参数是在端口打开时阻塞等待的毫秒数。*/ |
| 32 | } catch (PortInUseException e) {} |
| 33 | try { |
| 34 | inputStream = serialPort.getInputStream();/*获取端口的输入流对象*/ |
| 35 | } catch (IOException e) {} |
| 36 | try { |
| 37 | serialPort.addEventListener(this);/*注册一个SerialPortEventListener事件来监听串口事件*/ |
| 38 | } catch (TooManyListenersException e) {} |
| 39 | |
| 40 | serialPort.notifyOnDataAvailable(true);/*数据可用*/ |
| 41 | |
| 42 | try { |
| 43 | serialPort.setSerialPortParams(9600, |
| 44 | SerialPort.DATABITS_8, |
| 45 | SerialPort.STOPBITS_1, |
| 46 | SerialPort.PARITY_NONE);/*设置串口初始化参数，依次是波特率，数据位，停止位和校验*/ |
| 47 | } catch (UnsupportedCommOperationException e) {} |
| 48 | |
| 49 | readThread = new Thread(this); |
| 50 | readThread.start(); |
| 51 | } |
| 52 | |
| 53 | public void run() { |
| 54 | try { |
| 55 | Thread.sleep(20000); |
| 56 | } catch (InterruptedException e) {} |
| 57 | } |
| 58 | |
| 59 | //串口事件 |
| 60 | public void serialEvent(SerialPortEvent event) { |
| 61 | |
| 62 | switch(event.getEventType()) { |
| 63 | case SerialPortEvent.BI:/*Break interrupt,通讯中断*/ |
| 64 | case SerialPortEvent.OE:/*Overrun error，溢位错误*/ |
| 65 | case SerialPortEvent.FE:/*Framing error，传帧错误*/ |
| 66 | case SerialPortEvent.PE:/*Parity error，校验错误*/ |
| 67 | case SerialPortEvent.CD:/*Carrier detect，载波检测*/ |
| 68 | case SerialPortEvent.CTS:/*Clear to send，清除发送*/ |
| 69 | case SerialPortEvent.DSR:/*Data set ready，数据设备就绪*/ |
| 70 | case SerialPortEvent.RI:/*Ring indicator，响铃指示*/ |
| 71 | case SerialPortEvent.OUTPUT_BUFFER_EMPTY:/*Output buffer is empty，输出缓冲区清空*/ |
| 72 | break; |
| 73 | |
| 74 | case SerialPortEvent.DATA_AVAILABLE:/*Data available at the serial port，端口有可用数据。读到缓冲数组，输出到终端*/ |
| 75 | byte[] readBuffer = new byte[20]; |
| 76 | |
| 77 | try { |
| 78 | while (inputStream.available() > 0) { |
| 79 | int numBytes = inputStream.read(readBuffer); |
| 80 | } |
| 81 | System.out.print(new String(readBuffer)); |
| 82 | } catch (IOException e) {} |
| 83 | break; |
| 84 | } |
| 85 | } |
| 86 | } |
| 87 |
（2）写串口
| 1 | import java.io.*; |
| 2 | import java.util.*; |
| 3 | import javax.comm.*; |
| 4 | |
| 5 | public class SimpleWrite { |
| 6 | static Enumeration portList; |
| 7 | static CommPortIdentifier portId; |
| 8 | static String messageString = "Hello, world!/n"; |
| 9 | static SerialPort serialPort; |
| 10 | static OutputStream outputStream; |
| 11 | |
| 12 | public static void main(String[] args) { |
| 13 | portList = CommPortIdentifier.getPortIdentifiers(); |
| 14 | |
| 15 | while (portList.hasMoreElements()) { |
| 16 | portId = (CommPortIdentifier) portList.nextElement(); |
| 17 | if (portId.getPortType() == CommPortIdentifier.PORT_SERIAL) { |
| 18 | // if (portId.getName().equals("COM1")) { |
| 19 | if (portId.getName().equals("/dev/term/a")) { |
| 20 | try { |
| 21 | serialPort = (SerialPort) |
| 22 | portId.open("SimpleWriteApp", 2000); |
| 23 | } catch (PortInUseException e) {} |
| 24 | try { |
| 25 | outputStream = serialPort.getOutputStream(); |
| 26 | } catch (IOException e) {} |
| 27 | try { |
| 28 | serialPort.setSerialPortParams(9600, |
| 29 | SerialPort.DATABITS_8, |
| 30 | SerialPort.STOPBITS_1, |
| 31 | SerialPort.PARITY_NONE); |
| 32 | } catch (UnsupportedCommOperationException e) {} |
| 33 | try { |
| 34 | outputStream.write(messageString.getBytes()); |
| 35 | } catch (IOException e) {} |
| 36 | } |
| 37 | } |
| 38 | } |
| 39 | } |
| 40 | } |
| 41 |
来源：https://www.cnblogs.com/dyufei/archive/2010/09/19/2573911.html