Question

I use a byte array to fit 1024 bytes. The problem is, at separate times in my code I need to only use SOME of those bits. In C, I have used…

byte buff[] = read();
strcmp( buff, "CMD\r\n" );

This would ignore all later bytes in the array, and only compare the first 5 bytes. Is there an easy way to do this in Java?

Answer 1

You can compare an array of bytes with Arrays.equals( byte[], byte[] ).

byte[] buff = ...;
boolean isEqual = Arrays.equals( buff, 
                    "CMD\r\n".getBytes( Charset.forName( "US-ASCII" )));

EDIT: I missed that your byte array is 1024 bytes.

One option is to compare a slice of the byte array:

byte[] buff = ...;
final byte[] CMD_BYTES = "CMD\r\n".getBytes( Charset.forName( "US-ASCII" ));
boolean isEqual = Arrays.equals( Arrays.copyOf( buff, CND_BYTES.length()),
                    CMD_BYTES );

Another option is to convert the byte array up to a String, allowing an expression similar to C++.

byte[] buff = ...;
int buffLen = ...;
String command = new String( buff, 0, buffLen, Charset.forName("US-ASCII"));
int cmp = command.compareTo( "CMD\r\n");