ch38.htm

Java_by_Example,初级经典例子哦,珍藏版本

<B>increment</B>&nbsp;&nbsp;Increase the value of a variable.

<P>

<B>index</B>&nbsp;&nbsp;The same thing as a subscript. Used to

identify a specific array element.

<P>

<B>infinite loop</B>&nbsp;&nbsp;A loop that cannot stop executing

because its conditional expression can never be true.

<P>

<B>inheritance</B>&nbsp;&nbsp;In object-oriented programming,

the ability of a new class to inherit the data fields and functions

of another object.

<P>

<B>initialize</B>&nbsp;&nbsp;Set the starting state of a program

object. For example, you should initialize variables to a value

before you attempt to use them in comparisons and other operations.

<P>

<B>int</B>&nbsp;&nbsp;In Java, the <TT>int</TT> data type, which

is 32 bits long, can hold values in the range -2,147,483,648 to

2,147,483,647.

<P>

<B>integer</B>&nbsp;&nbsp;A whole-number value. For example, the

values 23 and -15 are both integers. (Notice that integers can

often be negative.)

<P>

<B>interface</B>&nbsp;&nbsp;A special type of Java class that

declares, but does not implement, a set of behaviors. Interfaces

allow Java programs to take advantage of a special type of multiple

inheritance.

<P>

<B>Internet</B>&nbsp;&nbsp;A huge world-spanning network of computers

that can be used by anyone with a suitable connection.

<P>

<B>I/O</B>&nbsp;&nbsp;Stands for input/output and refers to a

computer's ability to receive data (input) and send data (output).

<P>

<B>java</B>&nbsp;&nbsp;The Java interpreter.

<P>

<B>javac</B>&nbsp;&nbsp;The Java compiler.

<P>

<B>javadoc</B>&nbsp;&nbsp;A tool that automatically creates documentation

from Java source-code files.

<P>

<B>javah</B>&nbsp;&nbsp;A java tool used to create header files

for implementing native methods.

<P>

<B>javap</B>&nbsp;&nbsp;The Java disassembler, which converts

.CLASS files into a description of the original source code.

<P>

<B>jdb</B>&nbsp;&nbsp;The Java debugger.

<P>

<B>JPEG</B>&nbsp;&nbsp;Another type of graphical-image file format.

<P>

<B>leading</B>&nbsp;&nbsp;The amount of white space between lines

of text.

<P>

<B>literals</B>&nbsp;&nbsp;Values, such as a number or text string,

that are written literally as part of program code. The opposite

of a literal is a variable.

<P>

<B>local applet</B>&nbsp;&nbsp;An applet that's stored on your

computer system, rather than somewhere else on the Internet.

<P>

<B>logical expression</B>&nbsp;&nbsp;Results in a value of true

or false.

<P>

<B>logical operators</B>&nbsp;&nbsp;Operators like &amp;&amp;

(AND) and II (OR) that enable you to create logical expressions

that yield <TT>true</TT> or <TT>false</TT> results.

<P>

<B>long</B>&nbsp;&nbsp;In Java, the <TT>long</TT> data type is

64 bits in length and can hold truly immense numbers.

<P>

<B>loop</B>&nbsp;&nbsp;A program construct that enables a program

to perform repetitive tasks.

<P>

<B>method</B>&nbsp;&nbsp;A method is a function that's encapsulated

as part of an object.

<P>

<B>modal dialog box</B>&nbsp;&nbsp;A dialog box that must be dismissed

before the user can continue with the program.

<P>

<B>modeless dialog box</B>&nbsp;&nbsp;A dialog box that allows

the user to switch to another window while the dialog box is still

on the screen. The opposite of a modal dialog box.

<P>

<B>modular programming</B>&nbsp;&nbsp;Breaking a large program

down into a number of functions, each of which performs a specific,

well-defined task.

<P>

<B>multidimensional array</B>&nbsp;&nbsp;An array that must be

accessed using more than one subscript.

<P>

<B>multiple inheritance</B>&nbsp;&nbsp;When a class simultaneously

inherits methods and fields directly from more than one base class

simultaneously.

<P>

<B>multitasking</B>&nbsp;&nbsp;Running more than one computer

program concurrently.

<P>

<B>native methods</B>&nbsp;&nbsp;Functions that are written in

a language other than Java, but are called from within a Java

program. C++ is usually used to create native methods.

<P>

<B>nesting</B>&nbsp;&nbsp;When one program block is placed within

another program block.

<P>

<B>numerical expression</B>&nbsp;&nbsp;Combines numbers, variables,

or constants using operators.

<P>

<B>Oak</B>&nbsp;&nbsp;The original name of the Java programming

language.

<P>

<B>object-oriented programming</B>&nbsp;&nbsp;A programming paradigm

that treats program elements as objects that have data fields

and functions that act on the data fields. The three main characteristics

of OOP are encapsulation, inheritance, and polymorphism.

<P>

<B>one-dimensional array</B>&nbsp;&nbsp;An array that's set up

like a list and requires only one subscript to identify a value

contained in the array.

<P>

<B>operator precedence</B>&nbsp;&nbsp;Determines the order in

which mathematical operations are performed.

<P>

<B>order of operations</B>&nbsp;&nbsp;Same as operator precedence.

<P>

<B>override</B>&nbsp;&nbsp;In object-oriented programming, this

means replacing a method in a base class with a specific version

in a derived class.

<P>

<B>package</B>&nbsp;&nbsp;A collection of related Java classes.

<P>

<B>parameter</B>&nbsp;&nbsp;A value that is passed to an applet

or method. In the case of an applet, the parameters are defined

in the HTML document, using the <TT>&lt;PARAM&gt;</TT> tag.

<P>

<B>pass by reference</B>&nbsp;&nbsp;When an argument is passed

to a function by passing a reference to the actual value. In this

case, if you change the argument in the function, you also change

the original.

<P>

<B>pass by value</B>&nbsp;&nbsp;When an argument is passed into

a function by passing a copy of the value. In this case, changing

the copy doesn't affect the original value.

<P>

<B>pixel</B>&nbsp;&nbsp;The smallest dot that can appear on the

screen.

<P>

<B>platform-neutral language</B>&nbsp;&nbsp;A programming language

that can be used on any computer, regardless of the computer's

operating system.

<P>

<B>point</B>&nbsp;&nbsp;A unit of measurement of a font's height.

One point is equal to 1/72 of an inch.

<P>

<B>polymorphism</B>&nbsp;&nbsp;In object-oriented programming,

this is the ability for a new object to implement the base functionality

of a parent object in a new way.

<P>

<B>program flow</B>&nbsp;&nbsp;The order in which a program executes

statements.

<P>

<B>pseudocode</B>&nbsp;&nbsp;Program code that uses a general

type of syntax rather than being written using any specific programming

language. pseudocode is used to describe programming concepts

in a non-language-specific way.

<P>

<B>radio buttons</B>&nbsp;&nbsp;A group of checkboxes in which

only one checkbox can be selected at a time.

<P>

<B>remote applet</B>&nbsp;&nbsp;An applet that's stored on another

computer and which must be downloaded to your computer over the

Internet.

<P>

<B>runtime exception</B>&nbsp;&nbsp;An exception thrown by the

system in response to unexpected problems when an applet is running.

An example would be the exception generated when an applet attempts

to perform a division by zero.

<P>

<B>scope</B>&nbsp;&nbsp;A variable's scope determines where in

a program the variable can be accessed. In Java, a variable's

scope is determined by the program block in which it first appears.

<P>

<B>self-documenting code</B>&nbsp;&nbsp;This is program code that

is written in such a way that someone reading the code can understand

what the program is doing without having to read additional documentation.

One of the best ways to create self-documenting code is to use

carefully chosen constant, variable, and function names.

<P>

<B>server</B>&nbsp;&nbsp;A computer system that supplies services

to another computer called a client.

<P>

<B>short</B>&nbsp;&nbsp;In Java, the <TT>short</TT> data type

is sixteen bits in length and can hold values in the range of

-32,768 to 32,767.

<P>

<B>signature</B>&nbsp;&nbsp;A function or method's declaration

that shows function's return type, name, and arguments.

<P>

<B>signed</B>&nbsp;&nbsp;A value that can be either positive or

negative. This is the opposite of unsigned.

<P>

<B>single inheritance</B>&nbsp;&nbsp;When a class inherits methods

and fields directly from only one base class.

<P>

<B>spaghetti code</B>&nbsp;&nbsp;Program code that keeps jumping

from one place to another in the program without any apparent

organization.

<P>

<B>standalone application</B>&nbsp;&nbsp;In the context of the

Java language, an application that doesn't need to be embedded

in an HTML document. The opposite of an applet.

<P>

<B>stream</B>&nbsp;&nbsp;A flow of data between a source device

and a destination device. Commonly, a stream transfers data between

a disk file and memory.

<P>

<B>structured programming</B>&nbsp;&nbsp;A style of programming

in which the programmer divides his program's source code into

logically structured chunks of code.

<P>

<B>subclass</B>&nbsp;&nbsp;A class that inherits functionality

from another class called the superclass (or base class).

<P>

<B>subscript</B>&nbsp;&nbsp;A subscript is a number that identifies

the element of an array in which a value is stored. A subscript

is sometimes called an index.

<P>

<B>superclass</B>&nbsp;&nbsp;A class from which another class

inherits functionality. Also called a base class.

<P>

<B>symbolic constant</B>&nbsp;&nbsp;A word that represents a value

in a program. For example, the word PI could be used to represent

the value 3.14 in a program.

<P>

<B>tag</B>&nbsp;&nbsp;A command in an HTML document that identifies

the type of document component you're defining. For example, you

load and run an applet with an <TT>&lt;APPLET&gt;</TT> tag.

<P>

<B>thread</B>&nbsp;&nbsp;A single path of execution that is a

subprocess of the main process. All applications have at least

one thread, which represents the main program. An application

can create additional threads to handle multiple tasks concurrently.

<P>

<B>top-down programming</B>&nbsp;&nbsp;A style of programming

that divides tasks up into general modules. At the top level of

the program are only the general tasks, whereas, as you work your

way deeper into the program code, the programming becomes more

and more detailed.

<P>

<B>two-dimensional array</B>&nbsp;&nbsp;An array that's set up

much like a table, with a specific number of columns and rows.

<P>

<B>type cast</B>&nbsp;&nbsp;Tells Java's compiler that it's okay

to convert one type of value to another.

<P>

<B>unconditional branching</B>&nbsp;&nbsp;When program execution

jumps to a new part of the program regardless of any conditions.

<P>

<B>unicode</B>&nbsp;&nbsp;A new set of standard values for representing

the symbols used in text. The unicode character set is much larger

than the ASCII character set and allows for foreign-language symbols.

<P>

<B>unsigned</B>&nbsp;&nbsp;A value that can only be positive.

This is the opposite of signed. Unsigned numbers are not used

in Java programming.

<P>

<B>URL</B>&nbsp;&nbsp;Stands for Uniform Resource Locator, which

is a fancy name for what is really little more than an Internet

address.

<P>

<B>variable</B>&nbsp;&nbsp;A value that can change as often as

necessary during the execution of a program. Variables are always

represented by symbolic names.

<P>

<B>Web browser</B>&nbsp;&nbsp;An application used to access the

Internet's World Wide Web.

<P>

<B>World Wide Web</B>&nbsp;&nbsp;The graphical part of the Internet.

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