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Thu Jan 22 13:43:05 PST 2004


    A Glossary for the Java Language

      More on Java

      [ java.html ] [ java.syntax.html ] [ java.semantics.html ] [ java.packages.html ] [ java..class.tree..html ]

      See Also

      Roedy Green's Java Glossary for Novices: [ gloss.htm ]


      These are working notes and are being revised daily. I am open to corrections and improvements. Two question marks ?? indicate that I haven't found the data yet. If you have found the answer in any offical documentation please send it to where it will be incorporated with an acknowledgement.


    1. Overloading::=One name for several different types of object or function.
    2. Interfaces::=describes what you can do with a set of classes.
    3. Package::=unrelated collection of classes and interfaces. A file that starts with a package specifier P generates classes C in directory P with a file C.class that can be imported as P.* or P.C.


    4. default_modifier::=In the abscence of any modifiers fields are associated with objects and are visible in all classes in a package, and are inheritted by a subclass in the same package only.

    5. public::=A public variable or function can be used in any other class.

    6. private::=A private variable or function can only be used its own class.

    7. protected::= Protected variables and functions are inheritted by subclasses and are accessible within a package....only.

    8. private_protected::=`A private protected field or function can be inherrited by any subclass, but can not be used otherwise'.

    9. static::=A variable or fucntions associated with a class rather than with the objects of the class.

      Note for C programmers. In C a static variable declared in a functions is the same variable each time you call it. This is not available in Java. In C a static variable declared outside a function is shared by the set of functions in the same file and following the declaration an hidden from other functions. In Java a static variable is shared by all functions in that class. Whether other calsses can access it depend on whether it is private, public, and/or protected. A Java variable that is nonstatic is something that is not found in C. Each object in the class has its own variable, and all functions refer to that particular variable. The variable is cretaed as part of the object and deleted with it.

      In Java instance variables are the same each time you call them. A variable or function is declared to be static when it associated with the class of objects rather than a particular object in that class. This means that a static fucntion can not refer any data in an object - because it has no object. It also means that static data is essnetially shared in common by every object but only stored in a single place. If you are in doubt about whether some data should be static or not - ask yourself how many times it occurs: once per class(static) or once per object(not static) or many time per object (its in a different class!).

    10. final::=once initialized it can not be changed. A variable(a field of a class or object) is declared final when you want it to keep its initial value for ever. It makes it a constant variable. A class is declared as final if it can not be extended.

    11. native::=Preprogrammed in another language and running as machine code. For a tutorial on a way to integrate C functions into Java methods see [ index.html ]

    12. synchronized::=Only one thread can execute this at a time. A method or block of code is marked as synchronized if only one thread of control can be in it at a time. Other threads are locked out. The code is reentrant. It protects resources from interference by multiple access at one time.

    13. abstract::method=A method that must exist for objects in a class but is fully defined only in subclasses,
    14. abstract::class=A class with one or more abstract methods.
    15. abstract::=not concrete, not yet implemented, deferred, prototypical. An abstract method is one that is defined in classes derived from this class. All subclasses have a version as defined in the base class or also declare it as abstract. Certain methods can not be abstract: constructors, static, private, those that override superclass methods. An abstract method makes the whole class abstract. A class that inherits an abstract method and does not overirde it is also an abstract class. An abstract class can not be used to declare or create objects. You can only call an abstract method via an object in a class that has extended the abstract class and defined all the abstract methods.

    16. threadsafe::= If another thread excuting this code at the same time can not change the value of a variable then the variable is threadsafe and the compiler may do clever things with it to make the code faster or smaller..

    17. transient::=something that does last longer than a function call. If an object can exist longer than a given persistent.... then its transient data does not have to be preserved when a function exits.


    18. applet::=A small program that can be sent across a network and interpreted safely on the receiving machine.
    19. AWT::=awt.
    20. awt::=Abstract windowing toolkit, another windowing toolkit. A set of machine independent classes that make it easier to create graphic user interfaces and output.
    21. bytecode::= [ byte_code] .
    22. byte_code::=a way of describing classes as a stream of byte oriented machine code for the Java Virtual Machine.
    23. file::=A collection of data. A Java source code file defines one or more classes, interfaces to be added to a package. [ class ] [ interface ] [ Package ]
    24. class::=Defines a collection of knowledge and know how. Classes are defined as declaring variables(fields) and functions(methods) associated with the objects of that class, and also with the class iteself.. [ function ] [ method ] [ object ] [ variable ]

    25. field::=A component or meber of a class that holds data about and object or about the class, a variable.
    26. function::computing=A named piece of code that returns a value and may also do something
    27. function::java=A piece of know-how attached to a class or accessed via an object

    28. interface::=Describes a set of classes in terms of what they can do for you, but allows each class to implement these methods in any way that you wish.

    29. JDK::=Java Development Kit: the compiler: javac, interpreter: java, and the classes. [ javac ] [ java ]

    30. method::=A piece of "know-how". A procedure or function that is associated with an object or to a class.

    31. object::=An instance of a class. [ class ]
    32. procedure::ComputerScience=`A named piece of code that does something for a caller'.
    33. procedure::java=a void function. [ function ]
    34. static::=something associated with a class rather than an object. [ class ] [ object ]

    35. variable::Java=A piece of data(knowledge) associated with a class or an object.

    36. virtual_machine::=A hypothetical machine that can be emulated on many different actual machines.
    37. void::=word used in place of a type to indicate that a function does not return a value. -- introduced in ANSI C and still confusing people 10 years later.

    38. womb::=Java applets are kept alive inside a running program on the hosts machine - this called the womb. It also stops the applet from doing things that might be insecure.


    39. null::Object=nonexistent object.

    . . . . . . . . . ( end of section A Glossary for the Java Language) <<Contents | Index>>

Formulae and Definitions in Alphabetical Order