002--JDK, JRE, JVM differences

JDK, JRE, JVM differences

1. JDK

Java Development ToolKit (Java Development Kit).

The JDK is the core of the entire Java, including the Java Runtime (Java Runtime Envirnment), a stack of Java tools (JAVAC/JAVA/JDB, etc.), and a Java-based class library (the Java API).

The JDK has the following three versions: the J2SE Standard Edition is a version we usually use; the Java EE Enterprise Edition uses this JDK to develop the EE application; J2ME is primarily used on mobile devices and embedded devices.

2. JRE

Java Runtime Enviromental (Java run-time environment).

Java Runtime Environment (JRE) is what we call the Java platform, all Java programs must be under the JRE to run. Includes JVM and Java core class libraries and support files.

It does not include development tools-compilers, debuggers, and other tools-compared to the JDK.

3. JVM

Java mechinal (Java Virtual machine).

The JVM is part of the JRE, a fictional computer that is implemented by simulating various computer functions on a real computer. JVM has its own perfect hardware architecture, such as processor, stack, register, etc., also has the corresponding instruction system.

The main task of the JVM is to interpret its own instruction set (that is, bytecode) and map it to the local CPU's instruction set or system call to the OS.

The Java language is a cross-platform operation, in fact, different operating systems, using different JVM mapping rules, so that it is independent of the operating system, the completion of cross-platform.

4. Difference

The JVM is part of the JRE and the JRE is part of the JDK

5. Other

The reality of our development is that we have developed our own Java programs using the JDK (calling the Java API), compiled our text Java files into Java bytecode using the compiler program in the JDK (Javac), and run these Java bytecode on the JRE, The JVM parses these bytecode and maps it to a CPU instruction set or system call to the OS.

002--JDK, JRE, JVM differences