Question about making the Queues in the Queue class

[ofreiberg]

public void put(T t) { if((back+1)%q.length==front%q.length) resize(); q[back++%q.length]=t; }

how does this line work/what exactly does this line do? lines 13-16

[cforster]

Here's an English description:

put an item called t of type T in the queue: if the array is full, resize it (ie if front is about to be back) then put the the item t at the back of the array.

the %q.length is used everywhere to make sure we always go around the edge of the array.