Java Translation

The Java compiler translates Java source code into a special representation called bytecode
• Java bytecode is not the machine language for any traditional CPU
• Another software tool, called an interpreter, translates bytecode into machine language and executes it
• Therefore the Java compiler is not tied to any particular machine
• Java is considered to be architecture-neutral
Input in Java: JOptionPane is a easy way to do dialog boxes, messages or inputs. You have to import it at the beginning of the program:
//A sample program. Sample.java import javax.swing.JOptionPane; // imports JOptionPane class
public class Sample { public static void main ( String args[] ) { JOptionPane.showMessageDialog ( null, "This is a sample program" );
Java source code
Machine code
Java bytecode
Bytecode interpreter
Bytecode compiler
Java compiler
OOP with Java Programming 2rd class – Department of Programming Dr. Ahmed Al-Salih College of IT- University of Babylon
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System.exit ( 0 ); //stops the program } }
There are different kinds of icons for a dialog box, just replace the last argument:
JOptionPane.PLAIN_MESSAGE // this is a plain message JOptionPane.INFORMATION_MESSAGE // this is a info message JOptionPane.ERROR_MESSAGE // this is a error message JOptionPane.WARNING_MESSAGE // this is a warning message
You can also use JOptionPane for dialog boxes for input, and assign them to variables, just put:
name= JOptionPane.showInputDialog("put your message here" );
Example import javax.swing.JOptionPane; //import class JOptionPane public class Addition { public static void main ( String args[] ) { String firstNumber, secondNumber; int number1, number2, sum;
//read in the first number from user as a string firstNumber = JOptionPane.showInputDialog ( "Enter first integer" );
//read in the second number from user as a string secondNumber =JOptionPane.showInputDialog ( "Enter second interger");
//convert numbers from type String to type int number1 = Integer.parseInt ( firstNumber); number2 = Integer.parseInt ( secondNumber); //add the numbers sum = number1 + number2; //display the results JOptionPane.showMessageDialog ( null, "The sum is " + sum,"Results",JOptionPane.PLAIN_MESSAGE); System.exit ( 0 ); //ends the program } }
OOP with Java Programming 2rd class – Department of Programming Dr. Ahmed Al-Salih College of IT- University of Babylon
15
? Java basic operator: We can divide all the Java operators into the following groups:
? Arithmetic Operators ? Relational Operators ? Bitwise Operators ? Logical Operators ? Assignment Operators
1- The Arithmetic Operators: Arithmetic operators are used in mathematical expressions in the same way that they are used in algebra. The following table lists the arithmetic operators: Assume integer variable A holds 10 and variable B holds 20