Post on 13-Jan-2016
Java means Coffee Java Coffee Beans
The name “JAVA” was taken from a cup of coffee
Introduction to JAVA
• High Level Programming Language (HLL)• Java, released in 1995, is a relatively new programming language. • Developed by James Gosling from Sun Microsystems and his team
Creating a Java Program
javac
.java
java
.class
• Java Program: a set of instructions for the computer to follow. The source code.
Saved as filename.java
• Data: data for the Java program
• Java Compiler (javac): translates the program from Java to a language that the computer can understand.
• Byte Code Program: the compiler translates Java into a language called byte-code. Byte code is the machine language for Java Virtual Machine (JVM).
filename.class
• Byte Code Interpreter (java): the interpreter (JVM) translates byte code into machine language (.exe)
• Machine Language: is the language the computer understands.
Parts of a Java Program
import java.io.*;public class Hello{ public static void main (String[ ] args) { System.out.println(“Hello."); System.out.print(“Welcome to Java Programming!"); }}
This is same as header file in C.This package is used for input and output.
Parts of a Java Program
import java.io.*;public class Hello{ public static void main (String[ ] args) { System.out.println(“Hello."); System.out.print(“Welcome to Java Programming!"); }}
Every Java program is a class. The program starts with the name of the class. The class name must be the same as the . java file you save.
Parts of a Java Program
import java.io.*;public class Hello{ public static void main (String[ ] args) { System.out.println(“Hello."); System.out.print(“Welcome to Java Programming!"); }}
A main method is needed for execution to start. This main method gets executed first. The array of strings parameter is must.
Parts of a Java Program
import java.io.*;public class Hello{ public static void main (String[ ] args) { System.out.println(“Hello."); System.out.print(“Welcome to Java Programming!"); }}
Output statements: the basic output statement in Java is the System.out.println( ) or System.out.print( )
Variables Most Often UsedData Type Keyword Kind of Value Bytes of Memory Range of Values
Character char 1 character 2 not applicable
Byte byte integer 1 -128 to127
Short integer short Integers 2-32,768 to 32,767
(-215 to 215 - 1)
Integer int Integers 4 -2,147,483,648 to 2,147,483,647(-231 to 231 - 1)
Long Integer long Integers 8-9223372036854775808 to
9223372036854775807(-263 to 263 - 1)
Float float Decimal values to 7 decimal digit precision 43.4e-38 to 3.4e38
positive and negative
Double double Decimal values to 15 decimal digit precision 8
1.7e-308 to 1.73e308 positive and negative
Boolean bool Boolean (Logical) valuesTrue or False 1 not applicable
Constant Variables
• Constant is a variable whose value does not change in the program.Eg: PI = 3.14
The keyword ‘final’ is used to define constant in JavaEg.
final int count = 100;final double PI=3.14;