Class bytecode file

One 、 Bytecode file

1. Concept

1.1 Bytecode file

• Source code .java After the file is compiled by the compiler, a bytecode file will be generated , Multiple... May be generated
• Bytecode file is a binary class file , The content is JVM Instructions , Not like it C, C++ Machine code directly generated by compiler

1.2 Bytecode instruction (Byte Code)

• JVM Instructions ： One byte long , An opcode that represents the meaning of a particular operation (opcode), And the number of operands followed by zero representing at most the parameters required for this operation (operand)
• Many instructions in the virtual machine do not contain operand, Contains only opcode

2. View by

• Direct use Notepad++, Need to install one HEX-Editor plug-in unit
• use java Of javap Instruction decompile operation
• use IDEA Of jclasslib Bytecode Viewer see

Two 、 analysis

1. File nature and internal data type