COP 3331
Object Oriented Analysis
and Design
Java Part I
Reference Learning Java DDC publishing Herst, Yamauchi, Adler
Java Part I
// First Java Program
// HelloWorld.java
Public class HelloWorld
{
public static void main (String args[])
{
System.out.println(“Hello World!”);
}
}
Reference Learning Java DDC publishing Herst, Yamauchi, Adler
Java Part I
The following compile sequence
occurs in Unix on Diablo.
• gaitrosd@diablo:~/java>javac HelloWorld.java
• gaitrosd@diablo:~/java>java HelloWorld
• Hello World!
Reference Learning Java DDC publishing Herst, Yamauchi, Adler
Java Part I
Primary Java Program Files
File
Definition
Function
javac.exe
The Java
compiler
Converts Java source code
into executable byte-code
java.exe
The Java
enterpreter
Runs the java program
appletview.exe
The applet view
Locally runs a java applet
from within an HTML file.
jdb.exe
The Java
debugger
Used to debug your Java
applications and applets
javah.exe
The Java C
header and stub
file generator
Creates C header files and
C stub files from a java
class, allowing your java
and C code to interact.
javap.exe
The Java class
file disassembler
Converts a compiled class
back into source code.
javadoc.exe
The Java API
documentation
generator
Generates HTML
documentation from Java
Source Code
Reference Learning Java DDC publishing Herst, Yamauchi, Adler
Java Part I
• General Java points to
remember:
– Java is case sensitive.
– Use ; (semicolon) to terminate
lines of code.
– Use { } (curly braces) to indicate
blocks of code for classes,
methods, if statements, and
loops.
– Use spaces for indentation to
make your code more readable.
Reference Learning Java DDC publishing Herst, Yamauchi, Adler
Java Part I
Commen Type
t
//
/*
*/
/** */
Function
C++
Everything after the // and until
the end of the line is treated as a
comment.
C
Everything between the /* and */
is treated as a comment even if it
crosses a line boundary.
Hypertext
Same as the C style comments
except that these comments are
read by Java’s documentation
generator, which can generated
HTML code from your
comments. You can include
HTML code in these comments.
Reference Learning Java DDC publishing Herst, Yamauchi, Adler
Java Part I
• Memory variables: Storage
space declared inside the
computer on memory is
allocated through memory
variables and constants.
• Java is strongly typed which
means that memory variables
can only hold their declared
type of data.
• There are two types of data
catetories:
– Simple types.
– Object types.
Reference Learning Java DDC publishing Herst, Yamauchi, Adler
Java Part I
Simple Types
Type
Size
byte
8 bits
char
16 bits (unsigned)
short
16 bits
int
32 bits
long
64 bits
float
32 bits
double
64 bits
boolean
1 bit
Simple data types are not based on any other type.
These sizes do not vary from machine to machine.
All numeric types are signed except character.
Java is case sensitive. Names of simple data types
Are in lower case as shown.
Reference Learning Java DDC publishing Herst, Yamauchi, Adler
Java Part I
Declaring Variables
Format:
data_type variable_name;
data_type variable_name =value;
Example:
int j;
char opt;
short I;
long L;
float F;
double D;
boolean ok;
//
//
//
//
//
//
//
integer
character
short integer
long integer
real number
64 bit real number
True/False
int I,j,k,l;
char Men = “A”;
Reference Learning Java DDC publishing Herst, Yamauchi, Adler
Java Part I
Arithmetic Operators
Operator
Meaning
Example
-
Unary negation
x = -y;
+
Addition
-
Subtraction
x=y-z-x;
*
Multiplication
z = x * y;
/
Division
z = x / y;
%
Modulus
n = x % 3;
++
Increment by 1
x++; ++y;
--
Decrement by 1
x--;
x= y + z + x;
Note: There is not operator for exponent. You must
use the Math.pow() function for this task.
Reference Learning Java DDC publishing Herst, Yamauchi, Adler
Java Part I
Comparison and logical Operators
Operator
Meaning
Example
!=
Not Equal
if(x != 100) y=Z;
<
Less then
if(x < 100) y=Z;
<=
Less then or equal to
if(x <= 100) y=Z;
>
Greater then
if(x > 100) y=Z;
>=
Greater then or equal if( <= 100) y=Z;
to
!
Not
Answer = !Answer;
&
And
if( x=100 & y==0 ) y=Z;
|
Or
if( x=100 | y==0 ) y=Z;
^
Exclusive Or
if( x=100 ^ y==0 ) y=Z;
&&
Short circuit And
if (x <3 && y==0) z=7;
||
Short circuit OR
if (x <3 || y==0) z=7;
On the short circuit operators, the next comparison
is not accomplished if it does not affect the outcome.
Reference Learning Java DDC publishing Herst, Yamauchi, Adler
Java Part I
Operator
Meaning
Example
~
Bitwise
compliment
x = ~x; //flips each bit.
&
Bitwise And
if(y&2 == 2)
|
Bitwise Or
x = 3|5; // result 7
^
Bitwise Xor
x=3^5; // Result 6
<<
Left Shift
x = 1<<2; // Result 4
>>
Sign
propagating
right shift
I = 8>> 2; // Result 2
>>>
Zero-fill right
shift
I = 8 >>>2;// result 2
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Java Part I
Conditional Execution
if(condition)
statement;
if(condition) {
statement1;
statement 2;
statemetn 3;
etc;
}
Reference Learning Java DDC publishing Herst, Yamauchi, Adler
Java Part I
if(condition)
{
statement1;
statement2;
}
else
{
statement1;
statement2;
}
Reference Learning Java DDC publishing Herst, Yamauchi, Adler
Java Part I
Switch Statements
switch (expression)
{
case value1: statements;
case value2: statements;
...
default: statements;
}
switch (input_char) {
case ‘y’: System.out.print(“Entered y”);
case ‘n’: System.out.print(“Entered n”);
default: System.out.print(“Don’t know”);
}
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Java Part I
Loops
for (initialize; condition; increment)
{
statements;
statements;
}
example:
for (i=1; i<100; i++)
{
System.out.print(i);
}
Reference Learning Java DDC publishing Herst, Yamauchi, Adler
Java Part I
while (condition)
{
statements;
statements;
}
while (J < 100) {
{
J = J + 1;
System.out.print(J);
}
Reference Learning Java DDC publishing Herst, Yamauchi, Adler
Java Part I
Command Line Arguments: In all Java applications,
the main() function accepts an argument, an
array of strings called args[]; This array contains
command line arguments.
For instance, if you entered the following on the
HelloWorld program:
java HelloWorld Arg1 Arg2 “Hello Again”
The args.length would equal three (3). and the
contents would be:
args[0] -> “Arg1”
args[1] -> “Arg2”
args[2] -> “Hello Again”
Reference Learning Java DDC publishing Herst, Yamauchi, Adler