How can I convert a string or multiple strings to different ranges in a byte array in Java?
I have a bunch of strings for fields like name, user id, email, etc. that need to go into a byte [] array of a certain size (1024 bytes).
I'd love to find a method / function that would allow me to simply use my bufferPosition index variable like this:
byteArray [bufferPosition] + = name + = userID + = email;
bufferPosition + = name.length () + = userID.length () + = email.length ();
So far, all I have found are ways to directly convert strings to byte arrays and some seemingly tedious ways to solve this problem (e.g. treating each element of the string as a character, converting to byte, creating a loop and inserting each element) ...
EDIT: Follow-up
I also have fields that are String [] arrays of 14 elements. This would be the most tedious part. Will I be able to use a similar one for each loop? I guess there is a very clever way to figure this out.
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Try this using System.arraycopy :
// some dummy data
byte[] myByteArr = new byte[1024];
String name = "name";
String userId = "userId";
int bufferPosition = 0;
// repeat this for all of your fields...
byte[] stringBytes = name.getBytes(); // get bytes from string
System.arraycopy(stringBytes, 0, myByteArr, bufferPosition, stringBytes.length); // copy src to dest
bufferPosition += stringBytes.length; // advance index
You can do it using a loop this way (using your field names):
String[] myFields = new String[]{name, userID, email}; // put your fields in an array or list
// loop through each field and copy the data
for (String field : myFields) {
byte[] stringBytes = field.getBytes(); // get bytes from string
System.arraycopy(stringBytes, 0, myByteArr, bufferPosition, stringBytes.length); // copy src to dest
bufferPosition += stringBytes.length; // advance index
}
You will need to make sure you don't exceed the bounds of the array, but this is a simple example.
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Slightly improved version (thanks to @Ryan J):
private static byte[] bytesFromStrings(final String... data) throws UnsupportedEncodingException {
final byte[] result = new byte[1024];
int bufferPosition = 0;
if (data != null) {
for (String d : data) {
final byte[] stringBytes = d.getBytes("UTF-8");
if (bufferPosition > 1023) {
break;
} else {
System.arraycopy(stringBytes, 0, result, bufferPosition, Integer.min(1024 - bufferPosition, stringBytes.length));
bufferPosition = Integer.min(bufferPosition + stringBytes.length, 1024);
}
}
}
return result;
}
.. with null / overflow handling and dynamic data :-)
EDIT: ... and some portability considerations. ( d.getBytes()
)
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