Need help on Java meanings

I'm currently trying to convert a Java application into VB6 code and I am not real familiar with Java so I have a few questions and hope someone can help me

The following variables are defined as int in the Java app:

clear
code_mask
datum

Now I come across tthe following and I don't know what they mean

break;

clear = 1 << data_size;

datum += ( ( (int) block[ bi ] ) & 0xff ) << bits;

continue;

datum >>= code_size;

datum = bits = count = first = top = pi = bi = 0;

In the below statement does top++ mean to increment top after or before the action takes place

pixelStack[ top++ ] = suffix[ code ];