Lecture_1_Java_Programming_2023tttttttttt.ppt

Java Programming Course
Lecture1
Organization of the course
Java basics
Prof. Mohammed A.M. Ibrahim
Java Programming 1

Course objectives
• Knowledge and understanding of the principles
of object oriented programming,
• Knowledge of and experience with (the syntax
and semantics of) Java, including important parts
of the Java API,
• Knowledge of and experience with solving simple
problems by the design and implementation
object oriented programs.
Java Programming 2

Contents of the lectures (provisional)
1. Java basics
2. Selection, iteration
3. Methods, specification
4. Array’s, algorithms
5. Application of classes, UML class diagrams
6. Implementation of classes
7. Inheritance
8. AWT, Swing, Java Interfaces, Events
9. Exceptions, File IOJava
10. Database Connectivity and Networking Classes
11. Utility classes
12. Written examination
Java Programming 3

What is the purpose of a program? How does it operate?
Manipulating data: (storing data, retrieving data,
combining
data, transforming data, …).
Data is stored in memory, it is manipulated by a
cpu (central
processing unit)
12
13
14
15
16
17
Memory
+
CPU
1
2
Java Programming
4

Low level language, high level language
Copy the contents of MEM13 to CPU1
Copy the contents of MEM15 to CPU2
Add the contents of CPU1 to the contents of CPU2
Copy the contents of CPU2 to MEM12
Low level statements:
MOV M13 C1
MOV M15 C2
ADD C1 C2
MOV C2 M12
High level statement:
som = getal1 + getal2;
Java Programming 5

Compilation of Pascal, C, C++, … programs.
Java Programming 6

Compilation and execution of a Java program
Java Programming 7

Tools for writing, compiling and executing Java programs
Texteditor => putting together the program text
Compiler => translation of program text to bytecode
Virtual machine => execution of bytecode
javac Hello.java //call of the compiler
java Hello //call of the virtual machine
Java Programming 8

Example program: class Hello
Text editor:
public class Hello{
public static void main(String[]
args){
System.out.println(“Hello”);
}
}
The file MUST be saved as: Hello.java
Java Programming 9

Result of the compilation and execution
Java Programming 10

Context, a Java Development Environment (IDE)
Java Programming 11

Class Hello
//example of a class structure
public class Hello{
//main method, driver of the program
public static void main(String[]
args){
//example of a (print)
statement
System.out.println(“Hello”);
}
}
Java Programming 12

Basic ingredients of Java
Data types: collection of data elements + operators
Integer numbers: int byte, short, long
Floating numbers: double float
Logic values: boolean
Letters, digits, writing & reading signs: char
Text: String
Java Programming 13

Datatype int
Data elements: -2147483648 t/m
+2147483647
operators: +, -, *, / and %
3 / 4 -> 0 3 % 4 -> 3
5 / 4 -> 1 5 % 4 -> 1
Integer division Modulo division
All elements of the interval are available.
Java Programming 14

Datatype double
Data-elements: -1.8 * 10+308
t/m -4.9 * 10-324
,
0,
+4.9 * 10-324
t/m +1.8 *
10+308
,
operators: +, -, *, /
3.0 / 4.0 -> 0.75
Floating point division
2 + 3.0 -> 5.0 automatic conversion
(double)2 + 3.0 -> 5.0 type cast
Java Programming 15

Storing data
During the execution of a program data is stored in
memory.
This data is retrieved and restored many times.
How much room is needed to store data?
At which location in the memory is the data stored?
How is data stored?
How is data retrieved?
Java Programming 16

Declaration of an int-variabele
int score;
A memory cell is allocated to store 1 int value.
The location of the memory cell is not available (hidden).
The memory cell is identified by the name of the variable
score
Java Programming 17

Assignment operator =
public static void main(String[] args){
int x;
x = 10;
double d;
d = 34.67;
String s;
s = “abcd”;
}
Java Programming 18

Application of memory locations
int count; //creation of the
variable
count = 23; //storing data
System.out.print(count);
//retrieving, printing
count = count + 1; //retrieving,
storing
System.out.println(count); //
retrieving, storing
}
Java Programming 19

Application of memory locations (continued)
//creation, storing
double average = 4.5;
//retrieving, storing
average = average + 3.4;
//creation, storing
String name = “Ali”;
//retrieving, storing
name = name + “alHassany”;
}
Java Programming 20

Writing data: print() and println()
System.out.print(3);
System.out.println(13.5);
System.out.print(“The count is: “);
System.out.println(count);
System.out.println(3 * 4.5);
System.out.println(“Name:” + “Ali”);
System.out.println(“Count: “ + count);
System.out.println(“My name is: ” +
name);
Java Programming 21

Importing data: class Scanner
import java.util.*;
Scanner sc = new Scanner(System.in);
int count = sc.nextInt();
double average = sc.nextDouble();
String name = sc.next();
Java Programming 22

Example program
import java.util.*;
public class Example{
Scanner sc = new Scanner(System.in);
System.out.println(“Type an int-number:
“);
int number = sc.nextInt();
System.out.println(“The number is “ +
number);
}
}
Java Programming 23

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