1. Building Java programs using Command Line Window
INF120 Basics in JAVA Programming
AUBG, COS dept
Lecture 03
Title:
Building Java programs using Command Line Window
Reference: 1

2. Lecture Contents: Anatomy of a Java program (reminder)
More on elementary Java
Input/Output dialogs
Programming Style and Documentation
Building Java programs using DOS command lines

3. A Simple Java Program Listing 1.1
//This program prints Welcome to Java!
public class Welcome {
public static void main(String[] args) {
System.out.println("Welcome to Java!"); }

4. Two More Simple Examples
WelcomeWithThreeMessages
Run
ComputeExpression
Run

5. Anatomy of a Java Program
Class name
Main() method
Statements
Statement terminator
Reserved words
Comments
Blocks

6. Class Name
Every Java program must have at least one class. Each class has a name. By convention, class names start with an uppercase letter. In this example, the class name is Welcome.
//This program prints Welcome to Java!
public class Welcome {
public static void main(String[] args) {
System.out.println("Welcome to Java!"); }

7. Main Method
Line 2 defines the main method. In order to run a class, the class must contain a method named main. The program is executed from the main() method.
//This program prints Welcome to Java!
public class Welcome {
public static void main(String[] args) {
System.out.println("Welcome to Java!"); }

8. Statement
A statement represents an action or a sequence of actions. The statement
System.out.println("Welcome to Java!");
in the program below is a statement to display the greeting "Welcome to Java!“.
//This program prints Welcome to Java!
public class Welcome {
public static void main(String[] args) {
System.out.println("Welcome to Java!"); }

9. Statement Terminator
Every statement in Java ends with a semicolon (;).
//This program prints Welcome to Java!
public class Welcome {
public static void main(String[] args) {
System.out.println("Welcome to Java!"); }

10. Reserved words
Reserved words or keywords are words that have a specific meaning to the compiler and cannot be used for other purposes in the program. For example, when the compiler sees the word class, it understands that the word after class is the name for the class.
//This program prints Welcome to Java!
public class Welcome {
public static void main(String[] args) {
System.out.println("Welcome to Java!"); }

11. Blocks
A pair of braces in a program forms a block that groups components of a program.

12. Don’t confuse names parentheses, curly braces, square brackets, and angle brackets
Punctuation
Name
Typical use
Alternate names
( )
Parentheses
Round brackets
{ }
Curly braces
Curly brackets
[ ]
Square brackets
Box brackets,
Square braces
< >
Angle brackets
Chevron is <> with nothing in
Java Programming, Fifth Edition

13. Special Symbols

14. { … } // This program prints Welcome to Java! public class Welcome {
{ … }
// This program prints Welcome to Java!
public class Welcome {
public static void main(String[] args) {
System.out.println("Welcome to Java!"); }

15. ( … ) // This program prints Welcome to Java! public class Welcome {
( … )
// This program prints Welcome to Java!
public class Welcome {
public static void main(String[] args) {
System.out.println("Welcome to Java!"); }

16. ; // This program prints Welcome to Java! public class Welcome {
public static void main(String[] args) {
System.out.println("Welcome to Java!"); }

17. // … // This program prints Welcome to Java! public class Welcome {
public static void main(String[] args) {
System.out.println("Welcome to Java!"); }

18. " … " // This program prints Welcome to Java! public class Welcome {
public static void main(String[] args) {
System.out.println("Welcome to Java!"); }

19. Programming Style and Documentation
Appropriate Comments
Naming Conventions
Proper Indentation and Spacing Lines
Block Styles

20. Appropriate Comments
Include a summary at the beginning of the program to explain what the program does, its key features, its supporting data structures, and any unique techniques it uses.
Include your name, class section, instructor, date, and a brief description at the beginning of the program.

21. Naming Conventions Choose meaningful and descriptive names.
Variables and method names:
Use lowercase. If the name consists of several words, concatenate all in one, use lowercase for the first word, and capitalize the first letter of each subsequent word in the name. For example, the variables radius and area, and the method computeArea.
Class names:
Capitalize the first letter of each word in the name. For example, the class name ComputeArea, and the class name ComputeExpression.
Constants:
Capitalize all letters in constants, and use underscores to connect words. E.g. the constant PI, and MAX_VALUE

22. Proper Indentation, Spacing, Block Styles
Indent two spaces.
Spacing
Use blank line to separate segments of the code.
Use end-of-line style for braces.

23. .
More on
Elementary Java

24. JOptionPane - Input
For now Two ways of obtaining input are to be discussed.
Using the Scanner class (console input)
And methods like nextInt(), nextDouble(), hasNext(), …
Using JOptionPane input dialogs
And method showInputDialog() – to introduce now

25. Problem: Computing Loan Payments
This program lets the user enter the interest rate, number of years, and loan amount, and computes monthly payment and total payment.
ComputeLoan
Run

26. Getting Input from Input Dialog Boxes
String inp;
inp=JOptionPane.showInputDialog("Enter an input");
// OR
String inp = JOptionPane.showInputDialog(
"Enter an input");

27. Getting Input from Input Dialog Boxes
String string = JOptionPane.showInputDialog(
null, “Prompting Message”, “Dialog Title”,
JOptionPane.QUESTION_MESSAGE);

28. Converting Strings to Integers
The input returned from the input dialog box is a string. If you type a numeric value such as 123, it returns “123”. To obtain the input as a number, you have to convert a string into a number.
To convert a string into an int value, you can use the static parseInt() method in the Integer class as follows:
int intValue = Integer.parseInt(intString);
where intString is a numeric string such as “123”.

29. Converting Strings to Doubles
To convert a string into a double value, you can use the static parseDouble() method in the Double class as follows:
double doubleValue =Double.parseDouble(doubleString);
where doubleString is a numeric string such as “123.45”.

30. Problem: Computing Loan Payments Using Input Dialogs
Same as the program for computing loan payments, except that the input is entered from the input dialogs and the output is displayed in an output dialog.
ComputeLoanUsingInputDialog
Run

31. JOptionPane - Output
For now Two ways of sending output are to be discussed.
Using the System class, the out object
And methods System.out.print(), System.out.println()
Using JOptionPane message dialogs
And method showMessageDialog() – to introduce now

32. Displaying Text in a Message Dialog Box
you can use the showMessageDialog( ) method in the JOptionPane class. JOptionPane is one of the many predefined classes in the Java system, which can be reused rather than “reinventing the wheel.”

33. The showMessageDialog Method
JOptionPane.showMessageDialog(null,
"Welcome to Java!",
"Display Message",
JOptionPane.INFORMATION_MESSAGE);

34. What processing takes place?.
Building
Java programs Or
How Java works?
What processing takes place?

35. Compiling Java Source Code
You can port a source program to any machine with appropriate compilers. The source program must be recompiled, however, because the object program can only run on a specific machine.
Nowadays computers are networked to work together.
Java was designed to run object programs on any platform. With Java, you write the program once, and compile the source program into a special type of object code, known as bytecode. The bytecode can then run on any computer with a Java Virtual Machine, as shown below. Java Virtual Machine is a software that interprets Java bytecode.

37. Executing a Java program

38. JVM emulation run on a physical machine

39. JVM handles translations

40. Java Popularity
Pure Java includes 3 software facilities:
JRE
JVM
JDK

41. The Java Runtime Environment (JRE) provides
the libraries,
the Java Virtual Machine, and
other components to run applets and applications written in Java.

42. JVM - Overview
Java Virtual Machine is a program which executes certain other programs, namely those containing Java bytecode instructions.
JVM is distributed along with Java Class Library, a set of standard class libraries (in Java bytecode) that implement the Java application programming interface (API). These libraries, bundled together with the JVM, form the Java Runtime Environment (JRE).
JVMs are available for many hardware and software platforms. The use of the same bytecode for all JVMs on all platforms allows Java to be described as a write once, run anywhere programming language, versus write once, compile anywhere, which describes cross-platform compiled languages.
Oracle Corporation, the owner of the Java trademark, produces the most widely used JVM, named HotSpot, that is written in the C++ programming language.

43. JRE – Execution Environment
Oracle's Java execution environment is termed the Java Runtime Environment, or JRE.
Programs intended to run on a JVM must be compiled into Java bytecode, a standardized portable binary format which typically comes in the form of .class files (Java class files). A program may consist of many classes in different files. For easier distribution of large programs, multiple class files may be packaged together in a .jar file (short for Java archive).
The Java application launcher, java, offers a standard way of executing Java code.
The JVM runtime executes .class or .jar files, emulating the JVM instruction set by interpreting it or using a just-in-time compiler (JIT) such as Oracle's HotSpot. JIT compiling, not interpreting, is used in most JVMs today to achieve greater speed

44. JVM JVM architecture. Source code is compiled to Java bytecode, which
is verified, interpreted or
JIT-compiled for the
native architecture.
The Java APIs and JVM
together make up the
Java Runtime Environment
(JRE).

45. its primary components
JDK contents
The JDK has as
its primary components
a collection
of programming tools,
including:

46. JDK contents
appletviewer – this tool can be used to run and debug Java applets without a web browser
apt – the annotation-processing tool4
extcheck – a utility which can detect JAR-file conflicts
idlj – the IDL-to-Java compiler. This utility generates Java bindings from a given Java IDL file.
java – the loader for Java applications. This tool is an interpreter and can interpret the class files generated by the javac compiler. Now a single launcher is used for both development and deployment. The old deployment launcher, jre, no longer comes with Sun JDK, and instead it has been replaced by this new java loader.
javac – the Java compiler, which converts source code into Java bytecode
javadoc – the documentation generator, which automatically generates documentation from source code comments
jar – the archiver, which packages related class libraries into a single JAR file. This tool also helps manage JAR files.

47. JDK contents (cont.)
javah – the C header and stub generator, used to write native methods
javap – the class file disassembler
javaws – the Java Web Start launcher for JNLP applications
JConsole – Java Monitoring and Management Console
jdb – the debugger
jhat – Java Heap Analysis Tool (experimental)
jinfo – This utility gets configuration information from a running Java process or crash dump. (experimental)
jmap – This utility outputs the memory map for Java and can print shared object memory maps or heap memory details of a given process or core dump. (experimental)
jps – Java Virtual Machine Process Status Tool lists the instrumented HotSpot Java Virtual Machines (JVMs) on the target system. (experimental)
jrunscript – Java command-line script shell

48. JDK contents (cont.)
jstack – utility which prints Java stack traces of Java threads (experimental)
jstat – Java Virtual Machine statistics monitoring tool (experimental)
jstatd – jstat daemon (experimental)
keytool – tool for manipulating the keystore
pack200 – JAR compression tool
policytool – the policy creation and management tool, which can determine policy for a Java runtime, specifying which permissions are available for code from various sources
VisualVM – visual tool integrating several command-line JDK tools and lightweight[] performance and memory profiling capabilities
wsimport – generates portable JAX-WS artifacts for invoking a web service.
xjc – Part of the Java API for XML Binding (JAXB) API. It accepts an XML schema and generates Java classes

49. Creating, Compiling, and Running Programs

50. Creating, Compiling & Running Java
How is the required processing realized?
From the Command Line Window
From within IDEs

51. Creating, Compiling and Running Java from Command Line Window
First: to open a Command Window
Click Start; Select Run…; Type cmd
Second: to create a separate directory/folder on C: drive or Q: drive where to save .java and .class files
md INF120Progs
cd INF120Progs
Third: to Set path to JDK bin directory
Already done by OCC
Fourth: to create and save Java source file
Notepad/Write Welcome.java
Fifth: to Compile
javac Welcome.java
Sixth: to Run
java Welcome

52. Creating and Editing Using NotePad
To use NotePad, type
notepad Welcome.java
from the DOS prompt.

53. Creating and Editing Using WordPad
To use WordPad, type
write Welcome.java
from the DOS prompt.

54. Creating, Compiling, and Running Java Programs
In order to compile your Java program, you should type
javac Welcome.java
In order to run your compiled to bytecode Java program, you should type
java Welcome

55. Creating, Compiling, and Running Java Programs
Training session:
Create, compile and run the Java version of the “Hello, World!!!” program

56. Saving, Compiling, and Running, and Modifying a Java Application
Saving a Java class
Save class in file with exactly same name and .java extension
For public classes
Class name and filename must match exactly
Compiling a Java class
Compile source code into bytecode
Type javac First.java
Translate bytecode into executable statements Using Java interpreter
Type java First
Java Programming, Fifth Edition 56 56

57. Saving, Compiling, and Running and Modifying a Java Application (continued)
Compilation outcomes
Javac unrecognized command
Program language error messages
No messages indicating successful completion
Reasons for error messages
Misspelled command javac
Misspelled filename
Not within correct subfolder or subdirectory on command line
Java not installed properly
Java Programming, Fifth Edition 57 57

58. Running a Java Application
Class (file named First.class as result/output of Java compilation) stored in folder named for example
Java on C drive Or
in folder INF120Progs on Q drive
Run application from command line
Type java First
Shows application’s output in command window
Java Programming, Fifth Edition 58 58

59. Modifying a Java Class TASK:
Modify text file that contains existing class
Save file with changes
Using same filename
Compile class with javac command
Interpret class bytecode and execute class using java command
TASK:
Modify your “Hello, world!” program to a program that displays your name, your address and your postal address, each topic on a new line on the screen.
Java Programming, Fifth Edition 59

60. Creating a Java Application Using GUI Output
JOptionPane (import javax.swing.JOptionPane;)
Produce dialog boxes
Dialog box
GUI object resembling window
Messages placed for display
Package
Group of classes
The import statement
Use to access built-in Java class
Java Programming, Fifth Edition 60 60

61. Creating Java Application Using GUI Output
TASK:
Modify your “Hello, world!” program to a program that displays your name, your address and your postal address, each topic on a new output message dialog box.
Java Programming, Fifth Edition 61 61

62. Creating a Java Application Using GUI Output
import javax.swing.JOptionPane;
public class FirstDialog {
public static void main(String[] args)
JOptionPane.showMessageDialog(null,”First Java dialog"); }
Java Programming, Fifth Edition 62 62

63. Correcting Errors and Finding Help
First line of error message displays:
Name of file where error found
Line number
Nature of error
Next lines identify:
Symbol
Location
Compile-time error
Compiler detects violation of rules
Refuses to translate class to byte code.
Java Programming, Fifth Edition 63 63

64. Correcting Errors and Finding Help (continued)
Parsing
Process compiler uses to divide source code into meaningful portions
Logic error
Syntax correct but produces incorrect results when executed
Usually more difficult to find and resolve
Java API
Also called the Java class library
Prewritten Java classes
Java Programming, Fifth Edition 64 64

65. You Do It – training session
Your first application
Compile and run file First.java
Compile and run file FirstDialog.java (for more details see next slide)
Try to compile and run file ErrorTest.java
Adding comments to a class
Modifying a class
Java Programming, Fifth Edition 65 65

66. You Do It – training session
Creating a dialog box
Compile and run file FirstDialog.java
Modify program to produce two dialog boxes
JOptionPane.showMessageDialog(null, "First Java dialog");
JOptionPane.showMessageDialog(null, "Second Java dialog");
Modify program to produce three dialog boxes
JOptionPane var = new JOptionPane(); var.showMessageDialog(null, "Third Java dialog");
Java Programming, Fifth Edition 66 66

67. The jar utility pp 68-80

68. What is JAR? Java archive file can be used to group all the project files in a compressed file for deployment. The Java archive file format (JAR) is based on the popular ZIP file format.

69. The jar utility
JAR stands for Java ARchiver and it is used to compress and archive one or more files. It is equivalent to Zip file in Window OS. A typical .jar file contains Java class files in addition to source files as well as resource files, like images and properties. Let us see how to create
A regular Java archive (.jar) file and
A self-Executable Java archive file. An archive self executable file is nothing but a .jar file along with a manifest info containing the entry point of the Application specified in the form of class name.
For example, consider the following Java source files.

70. The jar utility – regular archive file
// File prog44.java:
import java.util.Scanner;
public class prog44 {
public static void main(String[] args) {
int a, b, c;
Scanner cin = new Scanner(System.in);
System.out.println("Enter two integers:");
a = cin.nextInt(); b = cin.nextInt(); c = a + b;
System.out.println("Result is = " + c);
System.out.println("Factoriel of result is " + factr(c)); }
static int factr(int n) {
if (n==0) return 1;
else return n*factr(n-1);

71. The jar utility
We must build the corresponding .class file using javac compiler.
javac prog44.java
This is the only class and it contains the main() method
Now, let us see how to create the regular jar comprising the above class. Java utility called jar.exe contains options for creating, listing, updating the jar file.
Q:\>jar cvf prog44.jar prog44.class
In the above command, the options can be interpreted as follows,
c - to create the archive file
v – to give verbose output during the jar file creation
f – the name of the jar file, ‘prog44.jar'

72. The jar utility Some more options:
t – list table of contents for archive
x – extract named (or all) files from archive
To list the contents of archive file, type command:
Q:\>jar tf prog44.jar
To extract files from archive, type command:
Q:\>jar xf prog44.jar

73. The jar utility
Now to list down the contents of the jar file, we have to use the 't' option along with 'v' and 'f' options,
Q:/>jar tvf prog44.jar
The above command will list down the contents of prog44.jar (including directories and files).

74. Viewing the Contents of a JAR File
You can view the contents of a .jar file using WinZip.

75. The jar utility
To extract the contents of a .jar file to the current working directory, we can use the 'x' option as used in the following command,
Q:\>jar xvf prog44.jar

76. The jar utility- self executable archive file
File ProgGeometricObject.java:
We must build the corresponding .class file(s) using javac compiler.
javac ProgGeometricObject.java
There are four .class files generated by the compiler:
Circle.class
GeometricObject.class
ProgGeometricObject.class – (includes main() method)
Rectangle.class
Now, let us see how to create the self executable jar comprising the above classes. When we invoke jar, we must point the entry point of the application using another option

77. jar utility- self executable archive file
e – specify application entry point for stand-alone application bundled in executable .jar file
To create self executable .jar file, type the command:
Q:\>jar cvfe Archive2.jar ProgGeometricObject *.class
To create regular .jar file, type command:
Q:\>jar cvf Archive1.jar *.class
Compare both Archive1 and Archive2 .jar files

78. The jar utility- self executable archive file
To run self executable .jar file, application we have to specify the '-jar' option like this command
Q:\>java –jar Archive2.jar OR
First: extract files and
Second: run JVM
Q:\>jar xf Archive2.jar
Q:\>java ProgGeometricObject

79. The jar utility- self executable archive file
To run self executable .jar file, type command
Q:\>java –jar Archive1.jar
No success
Archive1.jar has no specified entry point and therefore cannot consider it as self-executable archive file.

80. Practical session 5
Write a Java program to read a positive integer value n and to display:
The first n elements of the Fibonacci series
Save the source texts as Prog55.java
Build the corresponding .class file using javac compiler.
javac prog55.java
Run the program using
java prog55
Build an archive file using jar utility.
jar cvf prog55.jar prog55.class
Run the program through the archive file
java –jar prog55.jar

81. Thank You
For
Your Attention!
Any Questions?