Java Short Questions

• Give a description of the way that Input/Output is handled in Java. Your answer should include a comparison between the two sets of hierarchies of I/O streams: those based on InputStream and OutputStream, and those based on Reader and Writer.
• Describe the technique of layering I/O streams. Give some code for a client to show how this technique could be used to read doubles from files that arrive over a TCP/IP network.
• Give a piece of sample code to illustrate the way that exceptions are employed when reading text input from a file.
• Explain why you would need an object wrapper to use an ArrayList with elements of type double. Give some code to show how elements are inserted and accessed.

A class representing an electronic wallet contains three methods

• double getBalance()
• void debit(double amount)
• void credit(double amount)

An object of this class is to be incorporated into a server so that the functionality can be accessed via a network.

• If the system is based on sockets with a single connection between client and server, devise a protocol and explain the series of network transfers that take place if you wish to use the client to first check your balance and then credit by a certain amount.
• If the balance is not allowed to become negative, what additional features must be added to your protocol when debiting the account?
• Provide some code for the server side of this application.
• Explain the role of multithreading in servers.