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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.

Each platform thread consumes native resources, including stack reservation, and excessive runnable threads add scheduling and context-switching overhead. The service may hit native-thread creation errors or degrade before that point. Bound executors, measure queue depth and task latency, and apply backpressure rather than creating one thread per unbounded unit of work.

Read the top exception and every Caused by section. Framework and future wrappers often report where failure surfaced, not its origin. Preserve stack trace, request identifier, runtime version, and safe configuration context. When translating an exception, chain the original cause rather than logging only its message.

An object becomes eligible when no strong-reference path leads to it from roots such as live thread stacks, static fields, or JNI references. Eligibility does not guarantee immediate collection or finalization. To diagnose retention, inspect heap dumps and dominator paths; do not rely on System.gc() as a fix.

Capture repeated thread dumps with jcmd or jstack while the incident is active. A deadlock cycle shows threads waiting for locks held by each other; distinguish it from starvation or a slow dependency by checking whether owners can progress. Fix consistent lock order, shorten critical sections, or redesign ownership so both locks are not required together.

Read the final exception type/message, locate the failing operation, and inspect the nearest application frame that supplied its input. Reproduce the smallest failing case and trace where that value was created or transformed. Add validation at uncertain boundaries and a regression test; do not catch and suppress the exception at the bottom of the stack.