Difference between revisions of "ClassLoading"
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* The JVM uses a stack architecture with instruction operands being loaded onto an internal stack. | * The JVM uses a stack architecture with instruction operands being loaded onto an internal stack. | ||
* Early JVM's were interpreters - Next gen JVM's added JIT to compile bytecode to native code. | * Early JVM's were interpreters - Next gen JVM's added JIT to compile bytecode to native code. | ||
| + | |||
| + | = Loading the classes = | ||
| + | |||
| + | * C/C++ require a linker to merge all compiled code from various source files, alongwith code from libraries to form a single executable. | ||
| + | * In case of Java, it's different. Linking compiled classes is performed by the JVM when it loads the classes into memory. | ||
| + | * E.g. Apps can be written to use interfaces with the actual implementation loaded at runtime. | ||
| + | * Basic principle is that classes are loaded when needed. | ||
Revision as of 10:00, 23 November 2012
Binary Class
- The binary class format is defined in the JVM spec. So compatible class files can be produced from any language definition.
- Every binary class starts with the "cafe babe" signature.
- Class format version numbers - minor and major.
- Bytecode is machine code for the JVM.
- The JVM uses a stack architecture with instruction operands being loaded onto an internal stack.
- Early JVM's were interpreters - Next gen JVM's added JIT to compile bytecode to native code.
Loading the classes
- C/C++ require a linker to merge all compiled code from various source files, alongwith code from libraries to form a single executable.
- In case of Java, it's different. Linking compiled classes is performed by the JVM when it loads the classes into memory.
- E.g. Apps can be written to use interfaces with the actual implementation loaded at runtime.
- Basic principle is that classes are loaded when needed.
