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This article to share with you is about JVM virtual machine refers to what, Xiaobian think quite practical, so share to everyone to learn, I hope you can read this article after some harvest, not much to say, follow Xiaobian to see it.

JVM stands for Java Virtual Machine, which refers to Java Virtual Machine, and JVM is a specification for computing devices that can be implemented in different ways (software or hardware).

JVM

JVM is the abbreviation of Java Virtual Machine, it refers to Java Virtual Machine, it is a fictitious computer, is realized by simulating various computer functions on the actual computer. JVM virtual machine has its own perfect hardware architecture, such as processor, stack, register, etc., and also has corresponding instruction system. JVM masks information about specific operating system platforms so that Java programs can run unmodified on multiple platforms simply by generating object code (bytecode) that runs on the JVM virtual machine. When a JVM virtual machine executes bytecode, it actually ends up interpreting bytecode into platform-specific execution of machine instructions.

JVM A specification for computing devices that can be implemented in different ways (software or hardware). The instruction set for compiling a virtual machine is very similar to the instruction set for compiling a microprocessor. A JVM virtual machine consists of a bytecode instruction set, a set of registers, a stack, a garbage collection heap, and a storage method domain.

A JVM virtual machine is a hypothetical computer that can run Java code. As long as the interpreter is ported to a particular computer according to the JVM specification, any compiled Java code is guaranteed to run on that system.

A JVM virtual machine is an imaginary machine that is implemented on an actual computer through software emulation. JVM virtual machines have their own imaginary hardware, such as processors, stacks, registers, etc., and also have corresponding instruction systems.

JVM Virtual Machine Overview

1. Why use JVM virtual machines

One of the most important features of Java is its platform independence. The use of JVM virtual machines is the key to achieving this feature. A common high-level language needs to be compiled into at least different object code if it is to run on different platforms. After the introduction of Java virtual machine,Java language does not need to be recompiled when running on different platforms. Java language uses patterns JVM virtual machines mask platform-specific information so that Java language compilers can run unmodified on multiple platforms by generating object code (bytecode) that runs on JVM virtual machines. When executing bytecode, JVM virtual machines interpret bytecode into platform-specific execution of machine instructions.

2. Who needs to know about JVM virtual machines

The JVM virtual machine is the foundation of the underlying implementation of the Java language, and anyone interested in the Java language should have a general understanding of the JVM virtual machine. This helps to understand some of the properties of the Java language and also helps to use the Java language. For software people who want to implement JVM virtual machines on a particular platform, compiler authors of the Java language, and people who want to implement JVM virtual machines on hardware chips, a deep understanding of JVM virtual machine specifications is required. Also, if you want to extend the Java language or compile other languages into Java bytecode, you need to know more about JVM virtual machines.

3. Data types supported by JVM virtual machines

The basic data types supported by JVM virtual machines for Java language are as follows:

byte://1 byte signed integer complement

short://2 byte signed integer complement

int://complement of 4 byte signed integer

long://complement of an 8 byte signed integer

float://4 byte IEEE754 single-precision floating-point number

double://8 byte IEEE754 double precision floating point number

char://2 byte unsigned Unicode character

Almost all Java type checking is done at compile time. Data of the primitive data types listed above does not need to be hardware marked when executed in Java. The bytecode (instruction) that operates on these primitive data types already indicates the data type of the operand. For example, the iadd, ladd, fadd, and dadd instructions add two numbers together, and their operand types are int, long, float, and double. The virtual machine does not have a separate directive for boolean types. boolean data is processed by integer instructions, including integer returns. Boolean arrays are processed using byte arrays. Virtual machines use floating-point numbers in IEEE754 format. Older computers that do not support IEEE formats can be very slow when running Java numerical programs.

The above is what JVM virtual machine refers to, Xiaobian believes that some knowledge points may be what we see or use in our daily work. I hope you can learn more from this article. For more details, please follow the industry information channel.

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