Previously we had begin with Java Tutorial beginners guide featuring – What is Java , features of Java Programming Language , Java editors and different Java editions and Java Application Types . Now on Java tutorial we begin with the section 2 that is about JVM – Java Virtual Machine . And also about the difference between JDK Vs JRE Vs JVM including other aspects of Java Virtual Machine .
Guys, to deep dive in java, let’s have a look how it works internally.
Mac OS is a computer operating system developed by Apple.This is a operating system with beautiful interface, however, to own a the computer of Apple with this operating system, you need to use a lot of money, normally with the double price than that of common computers using Windows operating system.Fortunately, you can experience the Mac OS right on your computer by installing a Mac OS. Java virtual machine free download - Parallels Desktop for Mac, RM IV Drum Addiction (Mac), OpenOSX WinTel, and many more programs. The Java properties indicate the location of the jar file, the name of the Main class, and the version of the JRE to be used. The other properties include a pointer to the icon file and to the Java application stub file that is the native executable. Creating Mac OS X Java Applications on Other Platforms. Managing Java versions on Mac OSX is a nightmare. I recently switched over to using JDK 1.7, deleting JDK 6 from my MacBook entirely (I also had traces of JDK 5 - this laptop has been updated a few times). IDAutomation Java Barcode Package for Mac OS v.9.11 The JavaBeans, Applets, Servlets and Class Libraries in this package may be used on any platform with a Java Virtual Machine, including Windows, Linux, MacOS, Unix, Solaris, HP/UX, AS/400 and OS/390 to integrate automated barcoding in Java.
A role of Java virtual machine (short form as JVM) is to execute Java bytecode. We can state that JVM is the component of the Java software platform where code execution happens. Right now over 5.5 billion computer are in the market which are JVM-enabled. JVM lives inside our PC/computer and byte code is the language for JVM. With the introduction of JVM, job of compiler becomes very easy as it only generate byte code for JVM rather than generating different machine code for each m/c which is the reason why java language is platform independent.
A JVM executes programs containing Java bytecode instructions and are generally implemented to run on existing operating system (windows etc). A JVM provides a run-time environment which enables features such as exception handling which in turns provides debugging capability for every software exception. A JVM is a part of Java Class Library (some inbuilt java classes in the form of bytecode) to provide basic functions to developer while doing coding in Java. These libraries with the JVM together named as Java Runtime Environment (JRE).
Microsoft visual studio ultimate 2012. JVMs are compatible and available for almost all hardware and software platforms. Due to this feature of using the same bytecode for all JVMs on all platforms makes Java to be known as a write once and run anywhere language. This clearly describe that JVM is a crucial component of the Java language. Java bytecode is an machine language which is typically compiled from Java (or from other programming languages).
HotSpot is the most used JVM which is written in the C++ programming language. JVM doesn’t understand Java code due to which we require java compiler that compiles source code and create .class file. This .class file is composed of byte code which JVM can understand. There are two main components of JVM – heap memory and garbage collector. We will discuss about both in detail in the upcoming discussion.
Contents
How JVM works
Now moving on with the Java tutorial section , we will see working of Java Virtual machine ie, how JVM works exactly.
Best apk games for android 2.2 free download. Look at the pictorial format that explains the working of JVM.
JVM Vs JRE Vs JDK
Now let’s sort out the difference between JVM ,JRE and JDK . How does these differ from each other – JVM Vs JRE Vs JDK .
JRE ( Java Runtime Environment )
Java Runtime Environment is within which the java virtual machine actually runs. JRE contains Java virtual Machine and other files except development tools (debugger and compiler). So developer can run the source code in JRE but he/she cannot develop and compile the code.
JVM ( Java Virtual Machine )
As per above discussion, JVM runs the program by using libraries and files provided by Java Runtime Environment.
JDK ( Java Development Kit )Java Vm For Mac Os X V1.4.1
Java Development Kit can be considered as the super-set of JRE. JDK includes all features that JRE has and over and above it contains development tools such like compiler, debugger etc.
Now we have discussed about what is JVM ( Java Virtual Machine ) and how JVM works . Also in depth we have discussed about the difference between JVM Vs JRE Vs JDK.
On the third session of Java Programming Tutorials we will discuss about the Java Basic Syntax and Java Environment Setup .
In the past two articles you have seen how to customize your Java application so that it looks and feels more like a native Macintosh application when running on Mac OS X without changing the end user experience on other platforms. A combination of runtime properties and coding changes that targeted Mac OS X specific APIs made a big difference to that audience.
Recall that Mac OS X is a melding of two worlds. Hard core UNIX programmers can pop open a Terminal window and write their Java code using vi and compile and run it from the command line. There is, however, the more traditional Mac audience that interacts with their computer through a friendly UI that follows Apple Human Interface guidelines.
In this article, we look at deploying your Java application. The technical geek audience might be happy with running a class with a
main() method from the command line but the wider audience expects a double-clickable icon that looks and acts like every other native application. In this article, we travel from one end of the spectrum to the other to broaden your potential user base.
Although you should 'test everywhere', your build machine may not be a Mac. Fortunately, as you will see, a double-clickable Macintosh application is just a directory with some special contents and a name that ends with
.app . Even on a Windows machine you should be able to modify your build script to package up a Mac-specific version of your application.
Primitive Distributions
Because Mac OS X ships with J2SE 1.4.1 and J2SE 1.3.1, you can distribute your application as class files or jar files and - in theory - your customer could run your application from the Terminal application. We start with these models and quickly move to double-clickable jar files and shell scripts.
Java Vm Download For Windows 10
For this article, use the Java Sound Demo as the running example. Download and unzip the zip file. Inside the
JavaSoundDemo directory you will find the source files inside of the src subdirectory, a jar file, audio files, and html files that we will not use.
Raw Class Files
As a developer, you don't think twice about compiling the source files and running the application using the command line. Compiling the eight files in the
src directory generates fifty class files. You can then run the sample application from the command line like this.
java JavaSound
The Java Sound Demo starts up. We haven't customized the application in any way so the menu appears at the top of the JFrame and not where Macintosh users expect. The application looks like this out of the box.
You have done this compile and run step so many times that you hardly think twice about it. Epson scanner driver for mac. Think of the least technical person you know and ask whether they would be likely to follow these steps to run your application if a competing application were easier to install and run.
This example demonstrates two separate areas of usability. Once we got the application up and running it looked good and ran fine. You would not, however, want to distribute an application to an end user this way. You would have to somehow bundle up the fifty class files for easy download and installation. You would then have to provide instructions for running the application using, in the case of Mac OS X, the Terminal application.
Jar Files
If you are going to have to package up the class files for distribution anyways, you may as well produce a jar file. And, if you are going to produce a jar file, it ought to be executable. In the case of the Java Sound Demo, the file
JavaSoundDemo.jar is executable. Because Mac OS X ships with the Jar Launcher application, the end user needs only double click on the jar file and the application will launch.
To make the jar file executable, the manifest must include the name of the Main class file. Unjar
JavaSoundDemo.jar with the command jar xvj JavaSoundDemo.jar . Here's the file META-INF/MANIFEST.MF .
Shell Scripts and Helper Applications
For larger or more complicated applications you are likely to have more than one jar file along with resource files. A common strategy for targeting multiple platforms is to include a batch file and a shell script. Choose the non-platform specific download from the NetBeans homepage. Inside of the bin subdirectory you will find applications for running NetBeans on a variety of platforms.
The shell script
runide.sh can be run from the command line like this.
sh runide.sh -jdkhome /Library/Java/Home
The NetBeans IDE starts up with this decidedly non-Mac OS X look and feel.
You could, of course, modify the shell script to modify this look and feel, but the NetBeans developers decided on a different approach. Even though the typical NetBeans audience member is technically competent, there should be a friendlier way to start the IDE. They have created a native Mac OS X application called
NetBeansLauncher .
The version of
NetBeansLauncher that is included in the generic NetBeans download is a good next step. You will see how the team took it farther in the next section. On a Mac OS X computer you can double click on the macosx_launcher.dmg file inside of the bin directory. This is a disk image. Drag the NetBeansLauncher from the expanded disk image back into the bin directory. Now double click on the NetBeansLauncher . The ReadMe file that was also in the disk image provides the following information about usage.
When launched for the first time, NetBeansLauncher needs to find NetBeans root directory. First it looks into NetBeansLauncher.app itself. If it does not find NetBeans root directory there user must specify NetBeans root directory manually.
For this download, the first time the user starts up the
NetBeansLauncher , they need to navigate to the netbeans directory. After that, double clicking on the NetBeansLauncher starts up the NetBeans IDE as if it were any other native Mac OS X application.
First Class Mac OS X Applications
If you download the Mac OS X disk image from the NetBeans distribution and mount it you may be surprised at the simplicity of what you find. Unlike the complex structure visible in the other distributions, you will see five files with documentation and a single application. To install, you can move this
NetBeansLauncher application anywhere on your hard drive. Double click on it and the NetBeans IDE starts right up.
This is the experience that is expected on Mac OS X. The package structure and complexity is hidden from the user and they can't accidentally move a file that renders the IDE unusable. In this section we'll look more closely at the package structure and how to create a Mac OS X application whether or not our build machine is a Mac.
Packages in Mac OS X
Consider again the sentence from the
NetBeansLauncher instructions that says in order to locate the NetBeans root directory, 'First it looks into NetBeansLauncher.app itself.' This implies that NetBeansLauncher is a directory with the name 'NetBeansLauncher.app'. In the mounted disk image, either right click or Ctrl-click on the NetBeansLauncher icon and choose to 'Show Package Contents'.
The structure is the same for all Mac OS X applications. There is a
Contents directory with an XML file named info.plist , a text file named PkgInfo, a MacOS directory, and a Resources directory. If you don't have a creator code registered with Apple the PkgInfo text file should contain only the following. Best mac program for managing iphone.
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If you have a creator code, use it in place of the question marks. Ordinarily the MacOS folder contains a small stub file that launches the Java VM. In this case the NetBeans team has written their own application. We will look more closely at a property list file in the next section. For now, take a look at the contents of the
Resources directory.
You can see the contents of the same
netbeans package inside of the Resources subdirectory. This is your key to deploying on Mac OS X. Add in the necessary pieces and then just bundle up your ordinary distribution in the appropriate location. If you have a more flexible build process you should also strip out those pieces that aren't needed for the Mac OS X application such as the Windows executables.
If you are interested in digging deeper into the structure of a Mac OS X application, you will find more information in the Apple publication Anatomy of a Bundle.
Creating 'Native' Java Applications on Mac OS X
If you develop on Mac OS X you can use the
Jar Bundler application to turn jar files into Mac OS X applications. Jar Bundler is distributed with the other developer tools and is located in Developer/Applications/ . Start it, select the 'Classpath and Files' tab and add the file JavaSoundDemo.jar .
Select the 'Build Information' tab. For 'Main Class', navigate to the
JavaSoundDemo.jar file again and select JavaSound from the drop down list. This list is populated by any classes in the jar file containing a main() method. Accept all of the default settings for the options. You can use the default Java application icon or you can create your own. The icon you see below started as a screen shot of the running Java Sound Demo and was transformed into an icon using the IconComposer application that is also distributed as part of the developer tools.
Press 'Create Application' and enter the name 'JavaSoundDemo'. A Mac OS X application is created for you. You can show the package contents of the generated application as before. https://eiqmgwz.weebly.com/teamviewer-for-mac.html. You can view the property list with Apple's Property List Editor or with any text editor. Kutools for mac. It is just an XML file with properties stored as name - value pairs.
The Java properties indicate the location of the jar file, the name of the Main class, and the version of the JRE to be used. The other properties include a pointer to the icon file and to the Java application stub file that is the native executable.
Creating Mac OS X Java Applications on Other Platforms
Take a look at the contents of the package that was generated by
Jar Bundler on Mac OS X.
On another platform you need to duplicate this structure. To create an application named 'JavaSoundDemo' on, say, a Windows machine, start by creating a directory and naming it
JavaSoundDemo.app . Next, create a subdirectory named Contents . Inside of Contents you will need a MacOS directory with the JavaAPplicationStub . You can create the PkgInfo text file and your Info.plist can also be generated by hand and should contain the following XML.
You will need a
Resources directory with a Java subdirectory into which you put the JavaSoundDemo.jar file. In other words, with the exception of the JavaApplicationStub and the music.icns file, everything else can be created on another platform.
If you use Ant you can easily add a target that takes your jar files, images, and other resources and bundles it up as a Mac OS X application bundle that includes the plist file and Java application stub in the appropriate locations. Every time you create a new build you will automatically have your Mac OS X version. You can also find a growing number of Ant tasks that automate some of the steps outlined in this article.
Summary
When it comes time to deploy your Java application, consider the ease of use of your target audience. Even developers appreciate the double clickable version of the NetBeans IDE. Creating a Java application that looks and feels like a native application does not require a lot of extra work and can easily be integrated into your build process even if your build machine runs a different operating system.
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