Week 8 Notes and Questions

Keywords revision and summary

Here is a table of some of the more Java-specific language keywords (as opposed to things like "if .. else") that you might come across. You can find a complete list in the Java Language Specification section 3.9.

abstract catch class

const extends final

finally implements import

instanceof interface native

new package private

protected public static

super synchronized this

throw throws transient

try volatile

Questions

Can you explain when the keywords in bold would be used (these are ones that we have referred to in previous sessions)?

Here are some questions that will require you to use classes from the standard class library:

Write a program using a "Stack" object that allows a user to type in numbers until the value -1 is seen, after which the numbers are displayed back in reverse order, e.g.
```
  % java Reverse
  Number ? 9
  Number ? 1
  Number ? 2
  Number ? 7
  Number ? -1
  In reverse order, the numbers are:  7 2 1 9
```
Write a program that will convert values from Hex to Decimal and vice versa. For example:
```
  % java Convert 1234
  1234 == 0x4d2

  % java Convert 0x63ffd
  0x63ffd == 409597
```

Write a program that will multiply two arbitrarily large integers, e.g.

  % java Multiply 2 3
  2 * 3 = 6

  % java Multiply 52652653652635 27384728734872634
  % 52652653652635 * 27384728734872634 = 1441878637448610235081603490590

Write a program that will tell you what day of the week your birthday is, e.g.
```
  % java MyBirthday 7 12
  This year your birthday is on a Sunday
```

Write a program that lists the files in a zipfile. E.g.

  % java ListZipContents nick.zip
  nick.dat
  fred.dat
  files/
  files/another.txt

Write a program that will extract the host name and path from a www address. E.g.

  % java WWW http://funky.reo.cpqcorp.net/nick/tutorial/week8-questions.html
  The host is funky.reo.cpqcorp.net
  The path is /nick/tutorial/week8-questions.html

You have a webserver running on your machine and can see from the logs that clients from addresses "16.37.9.14" and "16.37.9.124" are continually trying to access it. For some reason, the only tool you have at your disposal is a JDK.
Write a Java program that accepts an IP address on the command line and translates that address into a proper nodename. For example:
```
  % java NodeInfo 16.37.9.226
  16.37.9.226 is "alffa.reo.cpqcorp.net"
```
Use this program to find out who "16.37.9.14" and "16.37.9.124" are.

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abstract	catch	class
const	extends	final
finally	implements	import
instanceof	interface	native
new	package	private
protected	public	static
super	synchronized	this
throw	throws	transient
try	volatile