1. acquaintance JVM

The concept of JVM

• JVM is a Java Virtual Machine for short. Means Java virtual machine.
• JVM software emulation of the Java bytecode instruction set.

specification

java language specification

• Syntax
  if-else-else if, and so the function syntax
• Lexical
  line terminators, white space, comments, identifiers, keywords, etc.
• java memory model
• Class loading process is connected
• abnormal
• ...

JVM specification

The main class file defines a binary JVM and JVM instruction set. Java language and the JVM is relatively independent, Groovy, Clojure, Scala, etc. can also be run in the JVM.

• Class File Format
• And storing the digital internal representation
  Byte -128 to 127 (-27 to 27 - 1)
• returnAddress data type definition
  pointer operation code. Java does not correspond to the data type can not be modified at runtime. Finally need to achieve
• The definition of PC, heap, stack, method area
• Integer, floating-point representations and definitions
• Special methods
  • <clinit>
  • <init>
• VM instruction set
  • The type of conversion
    l2i
    
  • Pop stack operation
    aload astore
  • Operation
    iadd isub
  • Process control
    ifeq ifne
  • 函数调用
    invokevirtual invokeinterface invokespecial invokestatic
• JVM need to provide the following support for Java Library
  • Reflection java.lang.reflect
  • ClassLoader
  • Initialize class and interface
  • Safety-related java.security
  • Multithreading
  • Weak references
• JVM compilation
  • JVM instructions corresponding to the source format
  • Jvp
  • JVM disassembly format
    (index) (opcode) [( operand1) [(operand2) ...]] [(comment)]