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How do you create and throw a custom exception class, and what constructors should a well-designed custom exception typically provide? What is the purpose of the addSuppressed() mechanism and getSuppressed() method on Throwable, and in what specific scenario does the JVM automatically populate suppressed exceptions? How does exception chaining (via the cause mechanism, initCause() or a constructor accepting a Throwable) preserve the original root-cause exception when wrapping and rethrowing a different exception type, and why does this matter for debugging? How would you design a custom exception hierarchy for an application, deciding when to create new exception classes versus reusing existing ones, and what fields/context should a well-designed custom exception carry? How would you implement a custom checked exception that requires additional context to be attached as the exception propagates up multiple layers of a call stack, without losing information at each layer? How does exception handling interact with generics and type erasure, specifically regarding why you cannot catch a generic type parameter as an exception type (catch (T e))? How would you design and implement a global, centralized exception-handling strategy for a Java application (such as a top-level handler in main(), or an uncaught exception handler for background threads), ensuring no exception silently crashes the application without being logged?
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How does exception handling interact with performance, particularly regarding the cost of filling in a stack trace, and how would you optimize exception usage in a performance-critical hot path?

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Constructing an exception (specifically, the fillInStackTrace() call invoked by Throwable's constructor, which captures the entire current call stack) has a genuinely measurable performance cost, disproportionately significant if exceptions are being thrown routinely as part of normal, expected control flow in a performance-critical hot path (an anti-pattern in itself -- exceptions should represent exceptional conditions, not routine control flow) -- for cases where you genuinely need lightweight, frequently-thrown exceptions (like in a high-throughput parser signaling routine, expected parse failures), overriding fillInStackTrace() to skip stack trace capture entirely (returning `this` without calling super) can eliminate this overhead, at the obvious cost of losing stack trace information for debugging that specific exception type.
// A lightweight exception for a high-frequency, expected control-flow scenario
public class FastValidationException extends RuntimeException {
    public FastValidationException(String message) {
        super(message, null, false, false);  // disables both suppression AND stack trace capture
    }
}

// vs. the default, which captures a full stack trace on every single construction --
// expensive if thrown thousands of times per second in a hot path
Real-world example A high-throughput data validation pipeline processing millions of records per minute switches its routine, expected-to-occur-frequently ValidationException to disable stack trace capture (using the four-argument Throwable constructor), measurably improving throughput since stack trace capture had become a significant fraction of total processing time at that volume.

Common follow-ups: Why is throwing exceptions for routine, expected control flow generally considered an anti-pattern in the first place, separate from the pure performance cost?;What's lost in debuggability by disabling stack trace capture, and how would you mitigate that trade-off?

Diagnostics & Performance;Design Patterns in Java
All 15 Exceptions questions