Java Glossary

Last updated 1998 June 16 by Roedy Green ©1996-1998 Canadian Mind Products.

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Name Server
a computer that provides the analog of telephone "directory assistance". You address somebody on Internet with a name like roedy@mindprod.com. Before you can start sending packets, that has to be converted to a numerical address, which is analogous to a phone number with area code. There are dedicated "directory assistance" computers that have lists of all the users in their area. Before you can send mail to someone, your computer may need to send a request to such a computer to look the number up for you.
native class
You can write machine-dependent C code and invoke it from Java. For multi-platform work, you need to implement the native routines for each platform. See JNI, JRI, RNI.
natural join
See join.
NCSA
National Center for Supercomputer Applications. They provide MOSAIC free to the public.
nested classes
See inner classes.
Net Components
NetComponents 1.1 is Oro's set of classes for applets or servers to support the IETF protocols including: FTP, NNTP, POP3, Telnet, TFTP, Finger, Whois, and other frequently used Internet protocols. Version 1.2 will add SMTP, IMAP4, and BSD R command support. See IETF.
NetRexx
IBM's hybrid Rexx/Java language that runs on the JVM interpreter. It has operator overloading, decimal arithmetic, native string parsing, safe coercions. Mike Cowlishaw, the designer of Rexx, created it. It is quite a bit terser than Java, partly because the compiler is smart enough to figure out the types of variables on its own, and builds the declarations for you. The code is much more readable than Java, requiring far fewer nested {} and (). The compiler generates Java source code, so it is quite possible to create projects with any mixture of NetRexx and Java. Methods start with the method keyword, which makes it easier to pick out all the methods from a source code listing. Loops can be named to make it easier to see where the loop ends. You also have the powerful Rexx parse command. My main complaints with the language are:
NETBEUI
NetBIOS Extended User Interface. Pronounced Net-booey. A simple efficient protocol used on small LANS originally developed by IBM in 1985. You see it mostly in Windows 95. The other two common LAN protocols are TCP/IP and Novell's IPX.
new
the keyword in Java that allocates new objects and initialises them. This is roughly the equivalent of C++'s new, C's malloc or object Pascal's create. There is no corresponding free. However, you can speed the garbage collector along by setting references to objects no longer needed to null. Let us say you created a Dalmatian object a subclass of Dog with new Dalmatian(). Here is the order of events:
  1. Allocate space for all the fields of both Dog and Dalmatian.
  2. Bulk zero all the space which effectively null/zeroes each Dog and Dalmatian field as appropriate.
  3. Do the member declaration initialisations of the Dog class to initialise the Dog fields.
  4. Do the constructor initialisations of the Dog class. Watch out! The constructor may use overridden methods that reference uninitialised Dalmatian fields.
  5. Do the member declaranion initialisations of the Dalmatian subclass to initialise the Damatian fields.
  6. Do the constructor initialisations of the Dalmatian subclass.
see constructor
newbie
An inexperienced Java programmers. I have written an essay on the tell-tale signs inexperienced Java programmers leave in their code.
news server
a computer on the internet that caches traffic from some subset of the possible newsgroup postings and allows you to access them a message at a time. If your local ISP does not handle the newsgroups you are interested in, have a look at this list of public news servers.
normal form
In SQL, there are five rules of sensible database design called the five normal forms. Briefy they are:
  1. No repeating groups of data within a row. Instead of having an Author1, Author2 and Author3 field, you should put the Author information in a separate table.
  2. Every non-key item must depend on the entire primary key. Don't replicate data that depends only on part of the key.
  3. Each non-key item must be a fact about the primary key item, not some other non-key item.
  4. Don't mix two different one to many relationships in the same table.
  5. Break tables up as small as possible so that each fact is recorded in only one place in the database. In practice, you have to balance this general rule against the extra overhead of many small tables.
normalization
cleaning up your SQL database design to follow the standard guidelines. See normal form.
null modem
Sometimes you have two computers (DTEs) that you wish to connect directly to each other. You have three choices.
1. Think back to your high school gym class where they taught ballroom dancing. If the number of boys did not exactly match the number of girls, some boys were given sashes, and told to dance backwards. Similarly, you can get one of your computers to masquerade as a DCE.
2. Buy a pair of modems and attach them back to back.
3. Make a cable with wires crossed in a particular way so that it simulates two modems back to back. This is called a null modem cable.
NumberFormat
java.text.NumberFormat converts Strings to and from doubles and longs. It can deal with commas and places past the decimal. It does not understand the concept of scaled integers, e.g. storing $1.49 as 149. Parse has the rather odd habit of sometimes returning a Long (not long) and sometimes a Double. You have to be prepared for either, and convert the Long to Double or vice versa yourself. NumberFormat's saving grace is that it adjusts to the current locale. Here is how it works:
// get an conversion object customised for a particular locale
java.text.NumberFormat nf = java.text.NumberFormat.getInstance();

// set whether you want commas (or locale equivalent) inserted
nf.setGroupingUsed(true);

// set how many places you want to the right of the decimal.
nf.setMinimumFractionDigits(3);
nf.setMaximumFractionDigits(3);

// set how many places you want to the left of the decimal.
nf.setMinimumIntegerDigits(1);
nf.setMaximumIntegerDigits(10);

// convert from binary to String
String s1 = nf.format(1234L); // will produce 1,234.000 not 1.234 !!
String s2 = nf.format(1.234D); // will produce 1.234

// convert from String to binary
Number n1 = null;
Number n2 = null;
try {
    n1 = nf.parse("1,234"); // will produce a Long 1234L
    n2 = nf.parse("1.234"); // will produce a Double 1.234D
    } catch (java.text.ParseException e) {}
Nutmeg
Thought Inc's Java implementation of the Smalltalk collection classes, such classes as Dictionary, Set, IndexedCollection, and Bag.



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