What's a good resizable, random access, efficient byte vector class in Java?

I'm trying to find a class for storing a vector of bytes in Java, which supports: random access (so I can get or set a byte anywhere), resizing (so I can either append stuff to the end or else manually change the size), reasonable efficiency (I might be storing megabytes of data in these things), all in memory (I don't have a file system). Any suggestions?I'm trying to find a class for storing a vector