与Java中的strcmp（）等效，用于比较字节数组

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");

Answer 2

Well it's trivial to write it yourself:

public static boolean truncatedEquals(byte[] x, byte[] y) {
    int upperBound = Math.min(x.length, y.length);
    for (int i = 0; i < upperBound; i++) {
        if (x[i] != y[i]) {
            return false;
        }
    }
    return true;
}

I don't believe there's anything built into Java for this.

Note that I've made the input two byte[] - bytes and strings are very different, and should be treated differently.