![First Java Program
Let us look at a simple code that will print the words Hello World.
Example
public class MyFirstJavaProgram { /* This is my first java program. * This will print 'Hello
World' as the output */
public static void main(String []args)
{
System.out.println("Hello World"); // prints Hello World
} }
Let's look at how to save the file, compile, and run the program. Please follow the
subsequent steps −
Open notepad and add the code as above.
Save the file as: MyFirstJavaProgram.java.
Open a command prompt window and go to the directory where you saved the
class. Assume it's C:.
Type 'javac MyFirstJavaProgram.java' and press enter to compile your code. If
there are no errors in your code, the command prompt will take you to the next
line (Assumption : The path variable is set).
Now, type ' java MyFirstJavaProgram ' to run your program.
You will be able to see ' Hello World ' printed on the window.](https://image.slidesharecdn.com/programminginjava-17i51ppt-211001070810/85/Programming-in-java-ppt-11-320.jpg)
![Comments line
Java supports single-line and multi-line comments
very similar to C and C++. All characters available inside
any comment are ignored by Java compile
public class MyFirstJavaProgram { /* This is my first java
program. * This will print 'Hello World' as the output *
This is an example of multi-line comments. */ public static
void main(String []args) { // This is an example of single
line comment /* This is also an example of single line
comment. */ System.out.println("Hello World"); } }
Output
Hello World](https://image.slidesharecdn.com/programminginjava-17i51ppt-211001070810/85/Programming-in-java-ppt-17-320.jpg)
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Programming in java ppt
- 1. Programming in Java-17I51 R.Lakshmi Asst.Prof Of IT E.M.G.Yadava Women’s College Madurai-14
- 2. Java Programming language. • Java is a high-level programming language originally developed by Sun Microsystems and released in 1995. Java runs on a variety of platforms, such as Windows, Mac OS, and the various versions of UNIX.
- 3. Reason for Learn java Programming Java is a MUST for students and working professionals to become a great Software Engineer specially when they are working in Software Development Domain. I will list down some of the key advantages of learning Java Programming: Object Oriented − In Java, everything is an Object. Java can be easily extended since it is based on the Object model. Platform Independent − Unlike many other programming languages including C and C++, when Java is compiled, it is not compiled into platform specific machine, rather into platform independent byte code. This byte code is distributed over the web and interpreted by the Virtual Machine (JVM) on whichever platform it is being run on. Simple − Java is designed to be easy to learn. If you understand the basic concept of OOP Java, it would be easy to master.
- 4. Secure − With Java's secure feature it enables to develop virus-free, tamper-free systems. Authentication techniques are based on public-key encryption. Architecture-neutral − Java compiler generates an architecture-neutral object file format, which makes the compiled code executable on many processors, with the presence of Java runtime system. Portable − Being architecture-neutral and having no implementation dependent aspects of the specification makes Java portable. Compiler in Java is written in ANSI C with a clean portability boundary, which is a POSIX subset. Robust − Java makes an effort to eliminate error prone situations by emphasizing mainly on compile time error checking and runtime checking.
- 5. Applications of Java Programming The latest release of the Java Standard Edition is Java SE 8. With the advancement of Java and its widespread popularity, multiple configurations were built to suit various types of platforms. For example: J2EE for Enterprise Applications, J2ME for Mobile Applications. The new J2 versions were renamed as Java SE, Java EE, and Java ME respectively. Java is guaranteed to be Write Once, Run Anywhere.
- 6. Multithreaded − With Java's multithreaded feature it is possible to write programs that can perform many tasks simultaneously. This design feature allows the developers to construct interactive applications that can run smoothly. Interpreted − Java byte code is translated on the fly to native machine instructions and is not stored anywhere. The development process is more rapid and analytical since the linking is an incremental and light-weight process. High Performance − With the use of Just-In-Time compilers, Java enables high performance. Distributed − Java is designed for the distributed environment of the internet. Dynamic − Java is considered to be more dynamic than C or C++ since it is designed to adapt to an evolving environment. Java programs can carry extensive amount of run-time information that can be used to verify and resolve accesses to objects on run- time.
- 7. History of Java James Gosling initiated Java language project in June 1991 for use in one of his many set-top box projects. The language, initially called ‘Oak’ after an oak tree that stood outside Gosling's office, also went by the name ‘Green’ and ended up later being renamed as Java, from a list of random words. Sun released the first public implementation as Java 1.0 in 1995. It promised Write Once, Run Anywhere (WORA), providing no-cost run-times on popular platforms. On 13 November, 2006, Sun released much of Java as free and open source software under the terms of the GNU General Public License (GPL). On 8 May, 2007, Sun finished the process, making all of Java's core code free and open-source, aside from a small portion of code to which Sun did not hold the copyright.
- 8. Java is − Object Oriented − In Java, everything is an Object. Java can be easily extended since it is based on the Object model. Platform Independent − Unlike many other programming languages including C and C++, when Java is compiled, it is not compiled into platform specific machine, rather into platform independent byte code. This byte code is distributed over the web and interpreted by the Virtual Machine (JVM) on whichever platform it is being run on. Simple − Java is designed to be easy to learn. If you understand the basic concept of OOP Java, it would be easy to master. Secure − With Java's secure feature it enables to develop virus-free, tamper-free systems. Authentication techniques are based on public-key encryption. Architecture-neutral − Java compiler generates an architecture-neutral object file format, which makes the compiled code executable on many processors, with the presence of Java runtime system. Portable − Being architecture-neutral and having no implementation dependent aspects of the specification makes Java portable. Compiler in Java is written in ANSI C with a clean portability boundary, which is a POSIX subset.
- 9. Robust − Java makes an effort to eliminate error prone situations by emphasizing mainly on compile time error checking and runtime checking. Multithreaded − With Java's multithreaded feature it is possible to write programs that can perform many tasks simultaneously. This design feature allows the developers to construct interactive applications that can run smoothly. Interpreted − Java byte code is translated on the fly to native machine instructions and is not stored anywhere. The development process is more rapid and analytical since the linking is an incremental and light- weight process. High Performance − With the use of Just-In-Time compilers, Java enables high performance. Distributed − Java is designed for the distributed environment of the internet. Dynamic − Java is considered to be more dynamic than C or C++ since it is designed to adapt to an evolving environment. Java programs can carry extensive amount of run-time information that can be used to verify and resolve accesses to objects on run-time.
- 10. Tools You Will Need For performing the examples discussed in this tutorial, you will need a Pentium 200-MHz computer with a minimum of 64 MB of RAM (128 MB of RAM recommended). You will also need the following softwares − Linux 7.1 or Windows xp/7/8 operating system Java JDK 8 Microsoft Notepad or any other text editor This tutorial will provide the necessary skills to create GUI, networking, and web applications using Java. Popular Java Editors To write your Java programs, you will need a text editor. There are even more sophisticated IDEs available in the market. But for now, you can consider one of the following − Notepad − On Windows machine, you can use any simple text editor like Notepad (Recommended for this tutorial), TextPad. Netbeans − A Java IDE that is open-source and free which can be downloaded from https://www.netbeans.org/index.html. Eclipse − A Java IDE developed by the eclipse open-source community and can be downloaded from https://www.eclipse.org/.
- 11. First Java Program Let us look at a simple code that will print the words Hello World. Example public class MyFirstJavaProgram { /* This is my first java program. * This will print 'Hello World' as the output */ public static void main(String []args) { System.out.println("Hello World"); // prints Hello World } } Let's look at how to save the file, compile, and run the program. Please follow the subsequent steps − Open notepad and add the code as above. Save the file as: MyFirstJavaProgram.java. Open a command prompt window and go to the directory where you saved the class. Assume it's C:. Type 'javac MyFirstJavaProgram.java' and press enter to compile your code. If there are no errors in your code, the command prompt will take you to the next line (Assumption : The path variable is set). Now, type ' java MyFirstJavaProgram ' to run your program. You will be able to see ' Hello World ' printed on the window.
- 12. Output C:> javac MyFirstJavaProgram.java C:> java MyFirstJavaProgram Hello World
- 13. •Java Identifiers •All Java components require names. Names used for classes, variables, and methods are called identifiers. In Java, there are several points to remember about identifiers. They are as follows − All identifiers should begin with a letter (A to Z or a to z), currency character ($) or an underscore (_). After the first character, identifiers can have any combination of characters. A key word cannot be used as an identifier. Most importantly, identifiers are case sensitive. Examples of legal identifiers: age, $salary, _value, __1_value. Examples of illegal identifiers: 123abc, -salary.
- 14. Java Modifiers Like other languages, it is possible to modify classes, methods, etc., by using modifiers. There are two categories of modifiers − Access Modifiers − default, public , protected, private Non-access Modifiers − final, abstract, strictfp We will be looking into more details about modifiers in the next section. Java Variables Following are the types of variables in Java − Local Variables Class Variables (Static Variables) Instance Variables (Non-static Variables)
- 15. Java Arrays Arrays are objects that store multiple variables of the same type. However, an array itself is an object on the heap. We will look into how to declare, construct, and initialize in the upcoming chapters. Java Enums Enums were introduced in Java 5.0. Enums restrict a variable to have one of only a few predefined values. The values in this enumerated list are called enums. With the use of enums it is possible to reduce the number of bugs in your code. For example, if we consider an application for a fresh juice shop, it would be possible to restrict the glass size to small, medium, and large. This would make sure that it would not allow anyone to order any size other than small, medium, or large
- 16. Java Keywords The following list shows the reserved words in Java. These reserved words may not be used as constant or variable or any other identifier names.
- 17. Comments line Java supports single-line and multi-line comments very similar to C and C++. All characters available inside any comment are ignored by Java compile public class MyFirstJavaProgram { /* This is my first java program. * This will print 'Hello World' as the output * This is an example of multi-line comments. */ public static void main(String []args) { // This is an example of single line comment /* This is also an example of single line comment. */ System.out.println("Hello World"); } } Output Hello World
- 18. Thank you