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Java Glossary
A - B - C -
D - E - F - G
- H - I - J
- K - L - M -
N - O - P - Q
- R - S - T -
U - V - W - X
- Y - Z
A
Applet
Applets are compiled Java programs which are run through
either an Appletviewer or from a web browser. Applets
run in their own frame (within the web page) and can do many
things including displaying graphics, playing sounds, and accepting
inputs (like mouse clicks or typing from the keyboard). Applets
are commonly used to add interactivity to websites.
To learn more see our What
is an Applet? page.
Applet Tag
To put your Java applet on a web page, you need to insert the
applet tag in the HTML of your website. The applet
tag looks like this: <applet code="HelloWorld.class"
width=200 height=50></applet>
For more information on making web pages and inserting applets
in your websites, see our Basic
HTML guide.
Application
An Application is a stand-alone Java program
that you generally run from the command prompt. You've used applications
before (probably without realizing what it was). For example,
when you type a paper using a word processor (like Microsoft Word),
you are using an application (although not necessarily
a Java application, it is an application none-the-less).
To learn more see our What
is an Applet? page.
Array
Arrays are a type of data structure that allows
you to store a number of values in a single structure. Arrays
basically allow you to put into one structure what you would normally
have to put into many variables. It makes organizing and finding
those values much easier since you don't have to keep track of
many different variables, you just have to keep track of the one
array.
Assignment
An assignment statement is used to give a value
to a variable. It looks like this:
B
Boolean
A boolean is a variable type that can only
have one of two possible values - TRUE or FALSE. Booleans
are commonly used in conditionals and loops.
Bytecode
Bytecode is the code generated by the Java compiler
that will make the Java Virtual Machine run on your computer.
It is basically an intermediate step between the code that you
write and the code that your computer executes.
To learn more see our
What is Java? page.
C
Char
A char is a variable type that represents a
single character. Chars can be any single letter,
number or any other type of single character.
Comment
Comments are used to make notes on your program
without affecting the code. By simply writing two slashes // before
any text that text will not be compiled. This is a good way to
take notes, explain complicated code, or to write for each function
what each parameter should mean and what is returned to ensure
the user knows what is going on.
Comparison
Comparison statements are used in Conditionals
and Loops. They usually look like this:
- "(x == 5)" - MAKE SURE TO USE TWO EQUAL
SIGNS!
- "(x > 5)"
- "(x < 5)"
Compile
A Java program is written in sourcecode and then compiled
into bytecode. This bytecode is then interpreted by the Java
Virtual Machine.
To learn more see our
What is Java? page.
Conditional
A conditional statement is a series of code
that allows the execution of portions of a program according to
the value of some Comparison statement. Conditionals use ‘if’, ‘else if’, and ‘else’s
to decide what code to execute based on a test statement of some
kind. Conditionals are basically like ‘if-then’ statements
in English. They usually look like this:
if (x == 5)
{
x = x + 19;
}
d
Do-While Loop
Do-while loops are similar to ‘while’ loops
except that they run through the body of the loop once before
checking the test statement. See ‘While Loop’ below for more information.
Double
A double is a numeric variable type that is
similar to a float. Doubles
are all real numbers, meaning that they can be used with decimals..
E
F
Float
A float is a numeric variable type that is
not only all integers, but includes all decimals as well. Floats are often used when an
exact division is necessary rather than division with no remainders.
For Loop
For loops are sections of code that are designed
to be repeated a certain number of times. For loops all include an initialization,
test statement and update in the initial line of code, followed
by the body of the loop. For
loops should be used when the exact number of times to repeat
is a known value. They are also helpful for iterating through
arrays. For loops
usually look like the code below:
for (int i = 0; i < intArray.length; i++)
{
intArray[ i ] ++;
}
Function
A function is a piece of code that is self-contained
in a program. Each function
should perform a specific task, and can be called from other
functions. A
function is ‘called’ by using a statement that calls
the name of a function followed by whatever necessary
parameters in parentheses after the name. Functions are the basic way of
organizing a program into smaller steps. Every function is declared by saying whether
it is public or private, whether it is void or returns a value,
its name, and any parameters.
For more on functions, see Lesson
6.
G
H
HTML
HTML stands for Hyper-Text Markup Language. It is the standard
language for creating websites (aka web pages).
To learn some basics of HTML, see our HTML
guide.
I
If Statement
An if statement is a conditional which states
that if some test statement is true, the code in the brackets
below the if statement should be executed.
If-Else Statement
An if-else statement is a conditional that
states that if some test statement is true, the code between the
brackets below the if statement should be executed. Otherwise, the code between the brackets
below the else statement should be executed.
Import
When you see import at the top of all of your
programs, those statements mean you are importing a certain portion
of the Java language to use in your program. These statements make it easier for the
compiler to do its job because it only has to compile the libraries
relevant to your program. It
also allows you to not have to refer to each type of object by
its full name, which usually includes the library path.
Inheritance
Inheritance in Java refers to when a class
‘extends’ another class. The
class that is defined as extending another class is the subclass. The subclass can use any variables or functions defined in the original class
(called the super class) as its own as long as they are not defined
as ‘private’.
int
An int is a numeric variable type. It is the
basic, generic variable for integer values.
Interpreter
A Java Interpreter is what actually translates
the compiled bytecode and executes that translation on the computer.
To learn more see our
What is Java? page.
J
Java
Java is a high-level, object-oriented computer
programming language.
To learn more see our
What is Java? page.
Java Virtual Machine (JVM)
The Java Virtual Machine is what is necessary
to be in place on any machine in order for Java bytecode to run
on that machine. Essentially,
the JVM makes it possible for Java to run on any type
of platform.
K
L
Loops
Loops are segments of code that are repeated either
for a designated number of times or until a certain test statement
is true.
See also For Loops, While
Loops, and Do-While Loops.
M
Method
See Function
n
O
P
Package
A package is basically a directory to store
files in. When writing
large programs with many files, these are often used to separate
different parts of the program into various directories. For example, if input and output is involved,
all of the files that have to do with input and output could be
put in an i/o package that could then be included in other files
when they are needed via import statements.
Private
Private sections of code (or variables) may
only be accessed by other portions of code in the same class.
Programming Language
A programming language is an artificial language
that can be translated by a compiler or some other mechanism into
a language that can be interpreted by a computer. It is basically an interface so that people
can give instructions to a computer.
Public
When you see the word public, it means that the
function or the variable that is being defined can be used by
any other function, class or program. This is the opposite of private functions, which may only be
accessed by other portions of code in the same class.
Q
R
S
String
A string is a variable type that stores text
data. Strings
are assigned values by either using an assignment statement to
another String type variable or by putting quotation
marks around the text that you want them to equal.
EXAMPLE: String name = “Andrew”;
Syntax
Syntax refers to the way that Java is written. For example, Java and C++ are different languages because
not only can they do different things, but their syntax
is different. They have
different ways of declaring arrays for example – i.e. their array
declaration syntax is different.
T
U
V
Variable
A variable is a piece of data associated with
a class or an object. A
variable is the interface between the user and the data
in the computer, a way for the user to call on that data.
Void
When you see the word void, it means that the
function it is associated with does not return a value. Any void function has no value and can not be
used like a variable like functions that return a value can.
w - z
While Loop
While loops are sections of code that are designed
to be repeated as long as a certain condition is met. While loops need all four essential parts of a loop: initialization,
test statement, update, and the loop body. In a while loop, the initialization happens before the loop. The test statement is the only thing in the parentheses after the word "while."
The update portion of a while loop actually occurs within the loop body. While loops
usually look like the code below:
int timesRolled
= 0;
while(timesRolled < 4)
{
RollDice();
timesRolled++;
}
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