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A class loader locates and defines bytecode; linking verifies it, prepares class storage, and resolves symbolic references as needed; initialization runs static initialization in the specified order. Parent delegation is common but custom loaders can change identity: classes with the same name loaded by different loaders are distinct runtime types. Class-loader leaks often arise when long-lived references retain an application loader after redeployment.

OutOfMemoryError identifies an allocation resource that could not be satisfied, such as Java heap, metaspace, direct buffers, or native threads. StackOverflowError usually indicates an excessively deep call chain or runaway recursion in one thread. Read the exact message, capture JVM and container metrics, and use a heap dump or thread stack evidence before changing memory flags.

False sharing occurs when separate variables frequently written by different cores share a hardware cache line. The values are logically independent, but cache-coherence traffic makes updates contend. Confirm with profiling and workload measurements before padding or using specialized structures; layout optimizations are hardware- and JVM-sensitive.