Learn java! every day A minute to understand the JRE and Jdk_java

Java source code is a *.java plain text file that can be written using any text editor, but this source is not executable. This task, which executes the source code, requires JDK and JRE.

The JDK is a Java language development package that compiles the *.java end of a file into a Java program that can be executed. Then, with a Java program that can be executed, a JVM is needed to run the Java program. The Java runtime Environment, which is the JRE, contains the JVM. The JVM is the Java virtual machine. Finally, a JRE is included in the JDK. With such a logical foundation, let's get to know both the JRE and the JDK separately.

Let's take a look at the JREfirst. The JRE is an abbreviation of the English Java Runtime Environment, which refers to the Java Runtime environment. It is a user of Java programs, not a developer. It is a collection of environments that are required to run Java programs, including JVM standards, implementations, and Java core class libraries. It can only complete the Java run, and can not compile or debug java. The JRE status is like a PC computer, we write WINDOWS32 or WINDOWS64 applications that require the operating system to help us run. Similarly, the Java program we write requires a JRE to run. The computer can run the Java application correctly only if the JRE is installed. The JRE has a separate version, and if a user only needs to run a Java program, then he only needs to install a JRE. And this JRE must appear in the C:\Program Files\java directory.

Let's look at the JDKagain. The JDK is the abbreviation of English Java Development Kit and is the Java language Software Development Toolkit. It is a Java suite for Java developer Publishing. The basic components included in the JDK include compilers, jar packaging tools, Javadoc document Builder, debug debugger, header file Builder, Disassembler, monitoring tools, and more. A completed JRE is included in the JDK. So, if you have the JDK installed, you don't have to install the JRE again. If your computer has both JDK and JRE installed, you will find that your computer has two JRE, a set of \jre located in the C:\Program files\java\jre1.5.0_15 directory, The following is a less server-side Java Virtual machine than the one in front, but simply copying the server-side Java Virtual machine in front of it. And in the installation JDK, you can choose whether to install the JRE located in the C:\Program Files\java directory.

Finally, let's talk about the JVMin passing. The JVM is a Java Virtual machine and is an abbreviation of the English Java Virtual machine. It is the most central part of the entire Java implementation, and all Java programs are first compiled into the. class file, which can be executed on a virtual machine. That is, class does not correspond directly to the machine's operating system, but is indirectly interacting with the operating system through a virtual machine that interprets the program to the local system for execution.

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