This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
I don't understand, how a object communicate with another object where both object from different class. I mean, how a object "a" created from class "X" will communicate with object "b" which created from class "Y".