java.util.regex.PatternSyntaxException [英] java.util.regex.PatternSyntaxException

问题描述

我修改了BluetoothChat代码以从微控制器接收串行数据到我的android手机.当我运行以下代码片段时，它给出了java.util.regex.PatternSyntaxException.错误到底是什么?为什么会发生这种异常?

I have modified the BluetoothChat code to receive serial data from a micro-controller to my android phone. When I run the following code snippet it gives java.util.regex.PatternSyntaxException. What exactly is the error? Why is this exception happening?

BluetoothChat.java

BluetoothChat.java

// The Handler that gets information back from the BluetoothChatService
private final Handler mHandler = new Handler() {
    @Override
    public void handleMessage(Message msg) {
        switch (msg.what) {

        case MESSAGE_WRITE:

            byte[] writeBuf = (byte[]) msg.obj;
            // construct a string from the buffer
            String writeMessage = new String(writeBuf);
            mConversationArrayAdapter.add(writeMessage);
            break;

        case MESSAGE_READ:

            byte[] readBuf = (byte[]) msg.obj;       

           // construct a string from the valid bytes in the buffer

            String readMessage = new String(readBuf, 0, msg.arg1);

            if(readMessage.matches("*"))
            {
               mConversationArrayAdapter.add("Left");
            }
            else

            {mConversationArrayAdapter.add(readMessage);}

 }

登录猫:

      09-15 13:54:32.070: E/AndroidRuntime(21931): FATAL EXCEPTION: main
      09-15 13:54:32.070: E/AndroidRuntime(21931): java.util.regex.PatternSyntaxException: Syntax         error in regexp
 pattern near index 1:
      09-15 13:54:32.070: E/AndroidRuntime(21931): *
      09-15 13:54:32.070: E/AndroidRuntime(21931):  ^
      09-15 13:54:32.070: E/AndroidRuntime(21931):  at java.util.regex.Pattern.compileImpl(Native Method)
      09-15 13:54:32.070: E/AndroidRuntime(21931):  at java.util.regex.Pattern.compile(Pattern.java:400)
      09-15 13:54:32.070: E/AndroidRuntime(21931):  at java.util.regex.Pattern.<init>(Pattern.java:383)
      09-15 13:54:32.070: E/AndroidRuntime(21931):  at java.util.regex.Pattern.matches(Pattern.java:413)
      09-15 13:54:32.070: E/AndroidRuntime(21931):  at java.lang.String.matches(String.java:1765) 09-15 13:54:32.070:
 E/AndroidRuntime(21931):   at
 com.example.footforthought.Sixth$2.handleMessage(Sixth.java:289)
      09-15 13:54:32.070: E/AndroidRuntime(21931):  at android.os.Handler.dispatchMessage(Handler.java:99)
      09-15 13:54:32.070: E/AndroidRuntime(21931):  at android.os.Looper.loop(Looper.java:137)
      09-15 13:54:32.070: E/AndroidRuntime(21931):  at   android.app.ActivityThread.main(ActivityThread.java:4517)
      09-15 13:54:32.070: E/AndroidRuntime(21931):  at java.lang.reflect.Method.invokeNative(Native Method)
      09-15 13:54:32.070: E/AndroidRuntime(21931):  at java.lang.reflect.Method.invoke(Method.java:511)
      09-15 13:54:32.070: E/AndroidRuntime(21931):  at  .android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:993)
      09-15 13:54:32.070: E/AndroidRuntime(21931):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:760)
      09-15 13:54:32.070: E/AndroidRuntime(21931):  at dalvik.system.NativeStart.main(Native Method)

推荐答案

matches()使用正则表达式(regex)来匹配输入，而 * 是正则表达式元字符，表示零个或多个前一个令牌.由于没有先前的标记，因此是语法错误.

matches() uses regular expressions (regex) for matching the input and * is a regex metacharacter, meaning zero or more of the previous token. Since there's no previous token, it's a syntax error.

如果您想直接匹配 * ，请使用反斜杠对其进行转义:

If you want to match * literally, escape it with backslash:

readMessage.matches("\\*")

或使用一些不使用正则表达式的字符串匹配函数，例如 equals().

or use some of the string-matching functions such as equals() that don't use a regular expression.

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