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Where the JVM Spends Time During Class Loading and Initialization
- Class loading in the JVM is done dynamically as classes are needed during program execution to conserve memory and avoid unnecessary preparation.
- The JVM utilizes class loaders in a hierarchical structure including Bootstrap, Platform, and Application ClassLoaders to locate and load classes.
- Parent delegation is a pattern where the JVM asks parent class loaders first before child loaders when loading classes to prevent duplication.
- Class loading can be delayed until a class is used, enabling the JVM to optimize startup times and memory consumption.
- Loading involves finding and reading the .class file into memory, but it does not yet initialize the class or set up static fields.
- Linking is the phase where the JVM checks the class structure, verifies bytecode safety, prepares static fields, and resolves symbolic references.
- Verification ensures the bytecode follows JVM rules for safety and type correctness, detecting errors like improper type conversions.
- Preparation allocates memory for static fields with default values without executing static initialization code.
- Resolution converts symbolic references to direct pointers during linking, enhancing runtime performance by replacing name lookups with quick memory access.
- Initialization runs static initializers, assigns values to static fields, and ensures class readiness for program execution.
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