Java - Glossary
The first two columns contain control characters, the third has special
symbols and punctuation, the fourth has numbers and special symbols,
the fifth and sixth have uppercase letters and special symbols, and the
last two columns have lowercase and special symbols. In JavaTM special symbols can be indicated by use
of a character escape sequence.
b6b5b4
b3b2b1b0
000 (0-15)
001 (16-31)
010 (32-47)
011 (48-63)
100 (64-79)
101 (80-95)
110 (96-111)
111 (112-127)
0000
nul
dle
space
0
@
P
`
p
0001
soh
dc1
!
1
A
Q
a
q
0010
stx
dc2
"
2
B
R
b
r
0011
etx
dc3
#
3
C
S
c
s
0100
eot
dc4
$
4
D
T
d
t
0101
enq
negAck
%
5
E
U
e
u
0110
ack
syn
&
6
F
V
f
v
0111
bell
etb
'
7
G
W
g
w
1000
bksp
cancel
(
8
H
X
h
x
1001
hTab
eom
)
9
I
Y
i
y
1010
lineFeed
subs
*
:
J
Z
j
z
1011
vTab
esc
+
;
K
[
k
{
1100
formFeed
fileSep
,
<
L
\
l
|
1101
carReturn
GrpSep
-
=
M
]
m
}
1110
shOut
recrdSep
.
>
N
^
n
~
1111
shIn
unitSep
/
?
O
_
o
del
Object.1
Essentially, a class is a set of objects having the same features, that
is , supporting the same queries and commmands. Class may be thought of
as the main building block in Java. Contains members, including fields
and methods. Classes are the "blueprint" for creating objects. code attribute in the <APPLET>
tag to give a complete specification of where to find the main applet
class file: code specifies the name of the file, and codebase specifies
the URL of the directory containing the file. // for
single line or to the end of this line, /*...*/
for multiple lines, and /**...*/ for javadoc comments used
to produce the API. new keyword. Constructors differ from methods
in that they return no data type, they have the same name as the class,
and have public visibility (except for abstract
classes which appropriately have protected
visibility). |
Escaped character |
Meaning |
Escaped character |
Meaning |
Escaped character |
Meaning |
| '\b' | backspace | '\n' | newline | '\0' | null |
| '\f' | form feed | '\t' | tab | '\"' | quotation mark |
| '\r' | carriage return | '\'' | apostrophe | '\\' | backslash |
Object class. Theif-thenstatement is the most basic of all the control flow statements. It tells your program to execute a certain section of code only if a particular test evaluates totrue. For example, theBicycleclass could allow the brakes to decrease the bicycle's speed only if the bicycle is already in motion. One possible implementation of theapplyBrakesmethod could be as follows:void applyBrakes(){
if (isMoving){ // the "if" clause: bicycle must be moving
currentSpeed--; // the "then" clause: decrease current speed
}
}If this test evaluates to
false(meaning that the bicycle is not in motion), control jumps to the end of theif-thenstatement.In addition, the opening and closing braces are optional, provided that the "then" clause contains only one statement:
Deciding when to omit the braces is a matter of personal taste. Omitting them can make the code more brittle. If a second statement is later added to the "then" clause, a common mistake would be forgetting to add the newly required braces. The compiler cannot catch this sort of error; you'll just get the wrong results.void applyBrakes(){
if (isMoving) currentSpeed--; // same as above, but without braces
}
Theif-then-elsestatement provides a secondary path of execution when an "if" clause evaluates tofalse. You could use anif-then-elsestatement in theapplyBrakesmethod to take some action if the brakes are applied when the bicycle is not in motion. In this case, the action is to simply print an error message stating that the bicycle has already stopped.void applyBrakes(){
if (isMoving) {
currentSpeed--;
} else {
System.err.println("The bicycle has already stopped!");
}
}
new
operator followed by the class name. An instance object contains all
variables and methods for this particular instance as well as access to
all class data and methods. Each instance of an object comes with
memory allocation for its own variables and methods.
System.out.println(data)
| Name | Type | Range | Default Value |
| boolean | boolean | true or false | false |
| byte | byte integer | -128 to 127 | 0 |
| char | character data | any character | '\0' (null) |
| short | short integer | -32768 to 32767 | 0 |
| int | integer | -231 to 231 - 1 | 0 |
| long | long integer | -263 to 263 - 1 | 0 |
| float | real | -3.4028E38 to 3.4028E38 | 0.0 |
| double | double precision real | -1.7977E308 to 1.7977E308 | 0.0 |
9876 / 1 = __________ 9876 % 1 = __________
9876 / 10 = __________ 9876 % 10 = __________
9876 / 100 = __________ 9876 % 100 = __________
9876 / 1000 = __________ 9876 % 1000 = __________
If you look for the pattern, you can see that integer division and modulo can be used to scale and shift integer values
Unlikeif-thenandif-then-else, theswitchstatement allows for any number of possible execution paths. Aswitchworks with thebyte,short,char, andintprimitive data types. It also works with enumerated types (discussed in Classes and Inheritance) and a few special classes that "wrap" certain primitive types:Character,Byte,Short, andInteger(discussed in Simple Data Objects ).The following program,
SwitchDemo, declares anintnamedmonthwhose value represents a month out of the year. The program displays the name of the month, based on the value of month, using theswitchstatement.class SwitchDemo {
public static void main(String[] args) {
int month = 8;
switch (month) {
case 1: System.out.println("January"); break;
case 2: System.out.println("February"); break;
case 3: System.out.println("March"); break;
case 4: System.out.println("April"); break;
case 5: System.out.println("May"); break;
case 6: System.out.println("June"); break;
case 7: System.out.println("July"); break;
case 8: System.out.println("August"); break;
case 9: System.out.println("September"); break;
case 10: System.out.println("October"); break;
case 11: System.out.println("November"); break;
case 12: System.out.println("December"); break;
default: System.out.println("Invalid month.");break;
}
}
}In this case, "August" is printed to standard output.
The body of a
switchstatement is known as a switch block. Any statement immediately contained by theswitchblock may be labeled with one or morecaseordefaultlabels. Theswitchstatement evaluates its expression and executes the appropriatecase.Of course, you could also implement the same thing with
if-then-elsestatements:int month = 8;
if (month == 1) {
System.out.println("January");
} else if (month == 2) {
System.out.println("February");
}
. . . // and so on
int or Object,
and a scope. A variable is a name for a location
in memory. A variable must be declared, specifying the variable's name
and the type of data that will be held in it. A variable can be given
an initial value in the declaration. This
value can be changed later in variables not declared final (constant),
using the assignment operator (=). See also class variable, instance variable, local variable, constant variable, attributes.
get and set
indicating the raw offset from GMT in milliseconds.1These definitions are as found in the Sun Glossary at http://java.sun.com/docs/books/tutorial/information/glossary.html
2Java Software Solutions Foundations of Program Design by John Lewis and William Loftus, Addison Wesley Longman Inc., p529.
3Introduction to Programming in Java: An Interdisciplinary Approach by
