# serialEvent out of bounds error
**URL:** https://discourse.processing.org/t/serialevent-out-of-bounds-error/11272
**Category:** Electronics (Arduino, etc.)
**Created:** [May 15, 2019, 1:44pm UTC](https://discourse.processing.org/t/serialevent-out-of-bounds-error/11272 "2019-05-15T13:44:45Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@alan856](https://discourse.processing.org/u/alan856)
#### Post date: [May 15, 2019, 1:44pm UTC](https://discourse.processing.org/t/serialevent-out-of-bounds-error/11272/1 "2019-05-15T13:44:45Z")
Below is the function causing the exception, followed by the error message. This HAD been working - not sure what I’ve done differently to ‘break’ it. Any ideas where to start looking?
=A.
```auto
void serialEvent(Serial comPort) {
try {
String comBuf = comPort.readStringUntil('\n');
if (comBuf != null) {
comBuf = trim(comBuf);
if (comBuf.equals("A")) {
comPort.clear();
isConnected = true;
wasConnected = true;
ardup = true;
comPort.write("U"); // let Ard know we are up
} else {
ardCmd= comBuf.charAt(0);
comPort.clear();
ardup = false;
evalData();
}
} else comBuf = ""; // keep it clean?
}
catch(RuntimeException e) {
e.printStackTrace();
}
}
```
And here is the error message produced by catch:
```auto
java.lang.StringIndexOutOfBoundsException: String index out of range: 0
at java.lang.String.charAt(String.java:658)
at Radar_V11.serialEvent(Radar_V11.java:210)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at processing.serial.Serial.serialEvent(Unknown Source)
at jssc.SerialPort$EventThread.run(SerialPort.java:1112)
```
---
### Author:  [@humayung](https://discourse.processing.org/u/humayung)
#### Post date: [May 16, 2019, 8:08am UTC](https://discourse.processing.org/t/serialevent-out-of-bounds-error/11272/2 "2019-05-16T08:08:12Z")
I suspected the error caused by `trim()`.
I copied the `trim()` description from [trim() / Reference / Processing.org](https://processing.org/reference/trim_.html)
> **Removes whitespace characters from the beginning and end of a String. In addition to standard whitespace characters such as space, carriage return, and tab, this function also removes the Unicode “nbsp” character.**
The error occurred on line (i think)
`ardCmd= comBuf.charAt(0);`
Probably, comBuf **only** contain whitespace characters, and then you trim it. so the length will be **zero**. This will cause
`StringIndexOutOfBoundsException`
error when you execute
`ardCmd= comBuf.charAt(0);`
because no char at position 0
Test case
```auto
String a = " "; // SPACES
char b;
void setup() {
try {
a = trim(a);
b = a.charAt(0);
}
catch(RuntimeException e) {
e.printStackTrace();
}
}
```
Further read: [https://developer.android.com/reference/java/lang/StringIndexOutOfBoundsException](https://developer.android.com/reference/java/lang/StringIndexOutOfBoundsException)
---
### Author:  [@alan856](https://discourse.processing.org/u/alan856)
#### Post date: [May 16, 2019, 10:28am UTC](https://discourse.processing.org/t/serialevent-out-of-bounds-error/11272/3 "2019-05-16T10:28:36Z")
Sorry - it was just the port was set to the wrong baud rate. Once corrected the code worked as it always had.