D286 Java Fundamentals - Set 5 - Part 3

Correct Answer: Compiling frequently executed bytecode into native code at runtime

The JIT compiler identifies hot bytecode paths during execution and compiles them to optimized native machine code, substantially improving long-running performance.

Correct Answer: Preventing the parameter variable from being reassigned in the method

A final parameter cannot be reassigned inside the method. It does not make the referenced object itself immutable.

Correct Answer: Calling a method on a reference that holds null

Attempting to dereference null, such as calling a method or accessing a field on a null reference, throws NullPointerException.

Correct Answer: Validating inputs and using Optional for values that may be absent

Validating parameters early and modeling absence explicitly with Optional makes the possibility of missing values visible and forces callers to handle it.

Correct Answer: Documenting and checking internal invariants during development

Assertions check conditions the developer believes always hold. Because they can be disabled at runtime, they must never be used to validate external input.

Correct Answer: Complexity is added without measured benefit, harming readability

Optimizing before profiling typically complicates code for negligible gain. Measurement should identify genuine bottlenecks before optimization effort is spent.

Correct Answer: Profiling data identifying actual bottlenecks

Profilers reveal where time and memory are actually consumed, which frequently differs from developer intuition, ensuring effort targets real bottlenecks.

Correct Answer: Failures are reported and diagnosed predictably

A consistent strategy for logging, wrapping, and propagating exceptions makes failures diagnosable and system behavior under error conditions predictable.

Correct Answer: Catching defects early while spreading knowledge and standards

Review catches defects and design problems before merge, spreads understanding of the codebase, and reinforces shared conventions across the team.

Correct Answer: Clear structure, tests, and consistent conventions understood by the team

Long-term maintainability comes from code that is easy to understand and safe to change, supported by tests, clear structure, and conventions the whole team follows.