10/10/2015Assoc. Prof. Stoyan Bonev1 COS240 O-O Languages AUBG, COS dept Lecture 10b Title: Running...

transcript

04/21/23 Assoc. Prof. Stoyan Bonev 1

COS240 O-O Languages AUBG, COS dept

Lecture 10bTitle:

Running Programs & IDEs(Java)

Reference: COS240 Syllabus

Lecture Contents:

• Java applications classified• Processing Java source texts

– How Java works– IDEs to run Java

Java programs may be applications or applets.

Applications are standalone programs, similar to .NET Console and Windows applications.

Applets are similar to applications, but they do not run as standalone programs.

- Instead, applets adhere to a set of conventions that lets them run within a Java-compatible browser (client-side).

- You can only run an applet from an HTML page.

Java applications classified

Java, C#, C++ - High Level PL

• In order to run /to execute/, any program written in HLL should be transformed to executable form

• Three ways to convert source code into executable form:– Compiler – generate object code– Interpreter – interpret the source code– Compiler of semi-interpreting type

Source program compiler

Results Object program

Executing computer

Compile time Run time

Results Source program

Interpreter

Compile time

Run time

Source program compiler

Results Object program in IL form

Interpreter

Compile2 time

Run time

Compile1 time

Processing HLL programs

• Java is compiled to intermediate form – bytecode. Bytecode processed by interpreter named JVM.

• C# and C++ (managed code) are compiled to intermediate form – MSIL code. MSIL code processed by interpreter named CLR.

• C++ (native, unmanaged code) is directly compiled to executable native machine code. No intermediate code, no need of interpreter.

How Java Works

• Java's platform independence is achieved by the use of the Java Virtual Machine (JVM).

• A Java program consists of one or more files with a .java extension

• these are just text (i.e. source) files.

• When a Java program is compiled, the .java files are fed to the compiler which produces a .class file for each .java file.

• The .class file contains Java bytecode. • Java bytecode is like machine language, but it is intended

for the Java Virtual Machine, not a specific processor.

Executing a Java program

JVM emulation run on a physical machine

JVM handles translations

Java Popularity

• Pure Java includes 3 software facilities:

• JRE

• JVM

• JDK

• The Java Runtime Environment (JRE) provides– the libraries,– the Java Virtual Machine, and– other components to run

applets and applications written in Java.

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.

JVM • JVM architecture.

Source code is compiledto Java bytecode, whichis verified, interpreted orJIT-compiled for thenative architecture. The Java APIs and JVMtogether make up theJava Runtime Environment(JRE).

JDK contents

The JDK has a collection

of programming tools, including:

JDK contents

• 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.

A Simple Java Program

//This program prints message “Welcome, Java!“// braces in new-line style

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

Listing 1.1

A Simple Java Program

//This program prints message “Welcome, Java!“// braces in end-line style (recommended)

public class Welcome {

public static void main(String[] args) { System.out.println("Welcome to Java!"); }}

Listing 1.1

Creating, Compiling, and Running Java Programs

Source Code

Create/Modify Source Code

Compile Source Code i.e., javac Welcome.java

Bytecode

Run Byteode i.e., java Welcome

Result

If compilation errors

If runtime errors or incorrect result

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

… Method Welcome() 0 aload_0 … Method void main(java.lang.String[]) 0 getstatic #2 … 3 ldc #3 <String "Welcome to Java!"> 5 invokevirtual #4 … 8 return

Saved on the disk

stored on the disk

Source code (developed by the programmer)

Byte code (generated by the compiler for JVM to read and interpret, not for you to understand)

Compiling Java Source CodeYou 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.

Java Bytecode

Java Virtual Machine

Any Computer

Java Programming: From Problem Analysis to Program Design, 3e 24

Approaches to run Java

• How to Compile/Run Java Programs– javac, java

• Java IDEs– TextPad, jGRASP, BlueJ, NetBeans, Eclipse

• Java Development Tools– javadoc, jar, jdb

Assoc. Prof. Stoyan Bonev04/21/23 25

Creating, Compiling & Running Java

From the Command Window

From within IDE

Creating, Compiling and Running Java from Command Line Window

First: to open a Command Window– Click Start, All Programs, Accessories, Command Prompt

Second: to create a separate directory/folder on C: drive or Q: drive where to save .java and .class files– md COS240Progs– cd COS240Progs

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

Creating and Editing Using editors like Notepad, WordPad, etc

To use NotePad, type notepad Welcome.java

from the DOS prompt.

To use WordPad, type write Welcome.java

from the DOS prompt.

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

Compiling, and Running Java Programs

public class Welcome {public static void main(String args[]) {

int i=1;while (i<5) {

System.out.println("Greeting to Blagoevgrad!");i++;

} // end of while loop } // end of method main} // end of Welcome class

Compiling and Running Java from IDEs

Java IDEs:– TextPad

– jGRASP

– BlueJ

– NetBeans – Open source by Sun

– Eclipse – Open source by IBM

Compiling and Running Java from TextPad

Edit the .java file The edited file should be saved before the coming

commands to take effect. Subjects of interest:

– Select tools, click run (user is expected to type command and parameters)

– Command:javac Parameter:Welcome.java

– Command:java Parameter:Welcome

– Select view, click tool output

public class COS240 {

public static void main(String args[]) {

int i=1;

for (i=1; i<=5; i++)

System.out.println("Greeting from COS dept");

Compiling and Running Java from jGRASP

Subjects of interest:Select Build, Click CompileSelect Build, Click Run

OrSelect Build, Click Run as Applet

OrSelect Build, Click Run as Application

CheckBox: run in MS-DOS window

import java.util.Scanner;

public class COS240Proba {public static void main(String args[]) {

Scanner cin = new Scanner(System.in);

int pom = cin.nextInt(); float pom2 = cin.nextFloat(); double pom3 = cin.nextDouble();

System.out.println(" " + pom + " " + pom2 + " " + pom3); }}

Compiling and Running Java from NetBeans

Subjects of interest: The concept of a project The user is expected: To choose project (Categories: Java, Projects: Java application) To name the project and to locate the project To create Main class and to set as Main project

To type the Java source text

To select Run, click Run Main Project (F6) Or To select Run, click Build Main Project(F11), click Run Main Project (F6) Or To select Run, click Clean and Build Main Project(Shift+F11), click Run Main Project (F6)

Compiling and Running Java from Eclipse

Subjects of interest: The concept of a project Compilation activated when File_save activity

take place List of steps to follow:

Compiling and Running Java from Eclipse Open the Java perspective:

– In main menu select Window > Open Perspective > Java Create a Java project

– In main toolbar Click New Java Project btn, Enter HelloWorld for name, click Finish

Create your Helloworld class– In main toolbar Click New Java class btn, select xx\src as a source

folder, enter HelloWorld for class name, click check box to create the main() method, click Finish

Add a println statement– Type stmts, then save changes, the class will automatically

compile upon saving Run your java application

– Right click on your class in the Package Explorer, and then select Run As>Java application

Eclipse

Downloads:– http://www.eclipse.org/downloads/

Tutorials:– http://www.vogella.de/articles/Eclipse/article.html

– http://eclipsetutorial.sourceforge.net/totalbeginner.html

Java Development Tools

Brief overview on Java Development Tools: (Detailed discussion in lecture 29)– java

– javac

– javadoc

– jar

– jdb

Running java

Synopsisjava [interpreter options] classname [program arguments]

java [interpreter options] -jar jarfile [program arguments]

Description

Common Options

Running javac

Synopsis– javac [options] files

Description

Common Options

Running javadoc

Synopsis javadoc [options] @list package… sourcefiles…

Description

Common Options

Running jar

Synopsis jar c|t|u|x [jarfile] [manifest] [-C directory] [input files]

jar I [jarfile]

Description

Common Options

Running jdb

Synopsis jdb [options] class [program options]

Description

Common Options

Practical session

• Task: write a program to input two integral values and to compute and display the result of their addition, subtraction, multiplication and division

• Language: Java

• IDE: Eclipse

Practical session

• Language: Java

• IDE: NetBeans

Practical session

• Language: Java

• IDE: jGRASP

Practical session

Problem:

To accumulate sum of stream of input integers terminated by sentinel value

• Language: Java

• IDE: Eclipse

Practical session

Problem:

• Language: Java

• IDE: NetBeans

Practical session

Problem:

• Language: Java

• IDE: jGRASP

Thank Youfor

Your attention!

10/10/2015Assoc. Prof. Stoyan Bonev1 COS240 O-O Languages AUBG, COS dept Lecture 10b Title: Running...

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