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我有一個設備，通過rs232與程序交流。設備發送消息和程序讀取一個字節的字節，並放入緩衝區，所以另一個線程解析緩衝區。 問題是，在消息中，我將有一個0x00字節{用於fifo緩衝區的空元素}，所以我不能在fifo中輸入該元素。如何解決該問題。 我用Fifo緩衝區，它允許空元素
BlockingQueue<Byte> queue = new ArrayBlockingQueue<>(1000);
對於在FIFO進入字節：
public void serialEvent(jssc.SerialPortEvent event) {
if (event.isRXCHAR()) {//If data is available
try {
buffer = serialPort.readBytes();
System.out.println(bytesToHex(buffer) + " event");
for (int i = 0; i < buffer.length; i++) {
queue.add(buffer[i]);
}
} catch (SerialPortException ex) {
System.out.println(ex);
}
而對於投票的元素
byte stx = queue.poll();
如何進入null元素，因爲消息將有一個空字節？
用於解析（線程解析）的代碼：
public void run() {
while (true) {
while (!queue.isEmpty()) {
System.out.println(queue.size() + " 1 proverka");
sb = new StringBuilder();
byte stx = queue.poll();
System.out.println(byteToHex(stx) + " parser");
if (stx == 0x02) {
sb.append(String.format("%02X ", stx));
System.out.println(queue.size() + " 2 proverka");
for (int i = 0; i < 3; i++) {
System.out.println(queue.size() + " 3 proverka " + i + " krug");
len[i] = queue.poll();
System.out.println(byteToHex(len[i]) + " parser");
輸出：
02事件 0000事件 01事件 4 1 proverka 77事件 2解析器 03事件 75事件 6 2 proverka 6 3 proverka 0 krug 線程「線程-1」中的異常java.lang.NullPointerException 在es.moduli.ingenico_card_reader.Ingenico_Card_Reader $ SerialParser.run（Ingenico_Card_Reader.java:127）
編輯與我的自定義字節級
/*
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* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package es.moduli.ingenico_card_reader;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.TimeUnit;
import java.util.logging.Level;
import java.util.logging.Logger;
import jssc.SerialPort;
import jssc.SerialPortEventListener;
import jssc.SerialPortException;
/**
*
* @author GiGo
*/
public class Ingenico_Card_Reader {
static SerialPort serialPort;
static BlockingQueue<CustomByte> queue = new ArrayBlockingQueue<>(1000);
final protected static char[] hexArray = "ABCDEF".toCharArray();
public void open() {
serialPort = new SerialPort("COM4");
try {
serialPort.openPort();//Open port
serialPort.setParams(9600, 8, 1, 0);//Set params
int mask = SerialPort.MASK_RXCHAR;//Prepare mask
serialPort.setEventsMask(mask);//Set mask
serialPort.addEventListener(new SerialPortEvent());//Add SerialPortEventListener
} catch (SerialPortException ex) {
System.out.println(ex);
}
SerialParser parser = new SerialParser();
parser.start();
}
public static String bytesToHex(byte[] bytes) {
char[] hexChars = new char[bytes.length * 2];
for (int j = 0; j < bytes.length; j++) {
int v = bytes[j] & 0xFF;
hexChars[j * 2] = hexArray[v >>> 4];
hexChars[j * 2 + 1] = hexArray[v & 0x0F];
}
return new String(hexChars);
}
public static String byteToHex(byte b) {
int i = b & 0xFF;
return Integer.toHexString(i);
}
public static int byteToIntBE(byte[] b) {
ByteBuffer bb = ByteBuffer.wrap(b);
bb.order(ByteOrder.BIG_ENDIAN);
int result = bb.getInt();
return result;
}
public static void sleep(long i) {
try {
Thread.sleep(i);
} catch (Exception e) {
}
}
public static String hexString(byte[] b) {
StringBuilder d = new StringBuilder(b.length * 2);
for (int i = 0; i < b.length; i++) {
char hi = Character.forDigit(b[i] >> 4 & 0xF, 16);
char lo = Character.forDigit(b[i] & 0xF, 16);
d.append(Character.toUpperCase(hi));
d.append(Character.toUpperCase(lo));
}
return d.toString();
}
public static class SerialPortEvent implements SerialPortEventListener {
byte buffer[];
@Override
public void serialEvent(jssc.SerialPortEvent event) {
if (event.isRXCHAR()) {//If data is available
//if (event.getEventValue() == 1) {//Check bytes count in the input buffer
//Read data, if 1 byte available
try {
buffer = serialPort.readBytes();
System.out.println(bytesToHex(buffer) + " event");
for (int i = 0; i < buffer.length; i++) {
queue.add(new CustomByte(buffer[i], true));
}
} catch (SerialPortException ex) {
System.out.println(ex);
}
}
// }
}
}
public static class SerialParser extends Thread {
StringBuilder sb = new StringBuilder();
Byte len[];
int len_mess = 0;
Byte mess[];
@Override
public void run() {
while (true) {
while (!queue.isEmpty()) {
System.out.println(queue.size() + " 1 proverka");
sb = new StringBuilder();
byte stx = queue.poll().getBufferByte();
System.out.println(byteToHex(stx) + " parser");
if (stx == 0x02) {
sb.append(String.format("%02X ", stx));
System.out.println(queue.size() + " 2 proverka");
for (int i = 0; i < 3; i++) {
System.out.println(queue.size() + " 3 proverka " + i + " krug");
len[i] = queue.poll().getBufferByte();
System.out.println(byteToHex(len[i]) + " parser");
//sb.append(String.format("%02X ", len[i]));
}
len_mess = (256 * 256 * len[0]) + (256 * len[1]) + (len[2]);
for (int i = 0; i < len_mess; i++) {
mess[i] = queue.poll().getBufferByte();
System.out.println(byteToHex(mess[i]) + "parser");
sb.append(String.format("%02X ", mess[i]));
try {
Thread.sleep(50);
} catch (InterruptedException ex) {
System.out.println(ex.getMessage());
}
}
byte etx = queue.poll().getBufferByte();
System.out.println(byteToHex(etx) + "parser");
if (etx == 0x03) {
sb.append(String.format("%02X ", etx));
System.out.println(sb.toString());
} else {
System.out.println("NOT ETX");
}
} else {
System.out.println("NOT STX");
}
System.out.println(sb.toString());
}
}
}
}
}
同樣的錯誤
02事件 0000017703事件 6 1 proverka 2 parser 75 event 6 2 proverka 6 3 proverka 0 krug 線程「Thread-1」中的異常java.lang.NullP ointerException 在es.moduli.ingenico_card_reader.Ingenico_Card_Reader $ SerialParser.run（Ingenico_Card_Reader.java:129）
我不知道我明白，你不能添加'null'到'queue'元素？ – fxm 2015-03-25 10:04:22
我添加和我檢查隊列的大小是2，但是當我輪詢的元素我在線程「線程1」中得到異常java.lang.NullPointerException – 2015-03-25 10:06:30
@GligorShijakovski：這是因爲你的'stx'變量的類型是'byte'而不是'Byte'，所以它是自動拆箱。 （話說回來，目前還不清楚爲什麼你不只是保持現有形式的字節0 ......） – 2015-03-25 10:06:55