Lecture 2

Lecture Topic:

Java code basics, data types and flow of control
Sample Quiz

Code-warrior:

Pascal

C++

MFC

IDE

Java

Group 1:: TrivialApp (Edit, Save, Compile, Run)
Appleframe.java
Classes.zip

SUN JDK Sparc 5 Solaris
IBM
Commands:: ls *.html
foo<html>html ( for keeping the original html file)
Example of Java program code:
// ExampleJavaApp.java
class ExampleJavaApp {: public static void main (String args[ ]) {
int x; // a value must be put into a variable before you can do anything with the variable
x = x + 1; // illegal - x has not yet been initialized
System.out.println("Hello form Java!");
}
}

in C or C++:
#include<stdio.h>

in Java:
import java.io.*;

Common in C or C++:
/* common */
// common

Common in Java:
// a single line common
/* common example */
/* A multiple line
common example
*/

Common in Java DOC:
/** common in java.doc*/
java.doc<foo.java>foo.html

Named Constants:
static final ID // in Java
#define PI 3.14 // in C, C++

Example:

class Wow {
static final double PI = 3.14159265358979323846

}

Characters:

Character type are defined 16-bit unsigned unique code values.
Char theChar = 'a';

it is possible to assign a numeric literal to a character typed variable and a character literal to an integer variable:
char theChar = 48;
integer theValue = 'a';

Data declaration:
type-name <follow by> variable-name

Symbol

meaning

the

boy

likes

Java

computer

( "," means followed by)

Then

S: the boy likes computer. Or S: the boy likes Java.

VD (variables declaration ) [modifies] type-name, variable( = initializes );

Public and Private:

public
private int i = 10;

private double[ ] foo;

public Integer[ ] foo = new Integer(100); // Integer is a class name

Flow of Control

Selection statement:
If expression:
expression if_true;
expression if_false;

Switch expression: // block
{ local_variable_declaration_and_statement }

'a' //OK

"hello" // illegal

LVD: (local_variable_declaration)

type_specification_variable

int i = 10;

statement empty statement;

labeled statement;

expression statement;

jump statement;

synch statement;

iteration statement;

examination statement;

Example

//Use of the Switch / General invokes of Brake

switch (expression) {

case const-1 :
statement_1;
break;

case const_2 :
statement_2;
break;

default:
statement;
break;

}

Sample Quiz

1. Character type are defined 32-bit unsigned unique code values.

True

False