Big data's basic Development of the first Java Program

Java is a technology for developing applications that can make Web more interesting and practical. Java is different from javascript, which is a simple technique for creating Web pages that can only be run in a browser.

Use Java to play games, upload photos, chat online and participate in virtual experiences, as well as access services such as online training, online banking and interactive maps. If Java is not installed, many applications and Web sites will not work.

By default, Java automatically notifies you that new updates are available to install. To ensure the latest software and computer security, be sure to accept and install the update. If you are notified to update Java on your Windows computer but you remember never downloading or installing it, it is possible that Java has been preloaded with your new computer.

What is JDK?

Java Development Kit is a product for Java developers and is the core of the whole Java

Including: Java runtime environment Jre, Java tools (javac/java/jdb, etc.) and Java basic class library (Java API,rt.jar, etc.).

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What is JRE?

Java Runtime Environment is a collection of environments needed to run Java programs, including Jvm standard implementation and Java core class library. Unlike the well-known Jdk, Jre is a Java running environment, not a development environment, so it does not contain any development tools (such as compilers and debuggers), but for users who use Java programs, only through it, Java developers can release their own programs to users' hands for users to use. Running Java programs generally requires users to install Jre; on their computers and cannot run without jre,java programs; without java programs, jre has no chance to show their talents. Including: virtual machine Jvm, running class library (runtime class libraries) and initiator (Java application launcher).

What is JVM?

Java Virtual Machine what we often call the Java virtual machine is the core part of the whole Java cross-platform implementation, which can run applications written in Java language.

All Java programs are first compiled into .class class files, and the Jvm virtual machine can execute the compiled class files, that is to say, class does not directly correspond to the machine's operating system, but interacts with the operating system indirectly through the virtual machine, and the virtual machine interprets the program as object code (different operating systems are different) and executes it to the local system. Jvm shields the information related to the specific operating system platform, so that Java programs only need to generate the object code running on the Java virtual machine and can run on a variety of platforms without modification. Only Jvm cannot be the execution of class, because when interpreting class, Jvm needs to call the class library lib needed for interpretation, that is, the lib class library in Jre, and Jvm alone has no effect.