Is an abbreviation JVM Java Virtual Machine (Java virtual machine), JVM is a specification for A computing device, which is a fictional computer, is passed over the actual computer simulation of various computer-implemented functions.
A very important feature of the Java language is platform-independent. The use of Java Virtual Machine is the key to achieving this characteristic. General high-level language if you want to run on different platforms, at least needs to be compiled into a different object code. And after the introduction of Java virtual machine language, Java language does not need to be recompiled to run on different platforms when. Java Virtual Machine using Java language information associated with a particular shielding platform, so that only Java language compiler to generate object code (bytecode) running in the Java virtual machine can run without modification on multiple platforms . Java Virtual Machine byte code, when executed, the bytecode interpreter into machine instructions executed on a particular platform. This is Java's ability to "compile once, run anywhere" reasons.
Generally by the JVM class loader subsystem (ClassLoader), the runtime data area, the execution engine, garbage collection four parts. In which the runtime data area we are most concerned about, which is the JVM memory part is a method area (Method Area), JAVA stack (Java Heap), a virtual machine stack (JVM Stack), the program counter, native method stacks (Native Method Stack) these parts.
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table of Contents
From the five comprehensive analysis of the JVM, performance optimization
1, JVM memory area is divided
2, JVM execution subsystem
3, the garbage collector and memory allocation strategy
4, efficient and elegant writing Java programs
5, performance optimization
A, JVM memory zoning
1. The program counter (thread-private)
2.Java stack (thread-private)
3. The native method stacks (thread-private)
4. heap (threads share)
The method area (threads share)
6. Direct Memory (threads share)
Two, JVM execution subsystem
1.Class class file structure
2. bytecode instruction
3. The class loading mechanism
4. The class loader
5.Tomcat class loading mechanism
6. Detailed Method Invocation
Third, the garbage collector and memory allocation strategy
In 1.Java is passed by value or reference passed?
2. The reference type
3. Basic garbage collection algorithm
4. generational garbage treatment
5.JAVA garbage collection GC type
Fourth, efficient and elegant writing Java programs
1. Object Oriented
2. Methods
3. General Programming
Fifth, performance optimization
1. Common performance evaluation / test indicators
2. Commonly used performance optimization tool
3 Application Performance Optimization Service
(1) asynchronous
(2) cluster
(3) application-related
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