Exceptions

Learn

Existing chapters for this concept.

• Exceptions

  Core Java

  Always use for files, streams, connections. Extend for checked, for unchecked.

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See it in code

Existing Java examples.

• core 18 Exceptions Demo

  Core Java · pkg1core/core18ExceptionsDemo.java · pkg1core · core18ExceptionsDemo.java

  - Throwable -> Error (don't catch) and Exception. - Checked exceptions (extend Exception) must be declared/handled. - Unchecked (extend RuntimeException) are…

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Prepare

Existing interview questions.

• Checked vs unchecked exceptions?

  Core Java — Interview Questions (200+)

  Checked must be declared/handled; unchecked (RuntimeException) need not be.

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• Can overriding method throw broader checked exceptions?

  Core Java — Interview Questions (200+)

  Clear naming, small methods, immutability, proper exceptions, tests, and idiomatic APIs.

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• InterruptedException meaning?

  Concurrency & Multithreading — Interview Questions (150+)

  Prefer immutability and high-level concurrency utilities over low-level locks.

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• ClassNotFoundException?

  JVM Internals & GC — Interview Questions (120+)

  Don't tune prematurely; measure.

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• Exceptions — Interview Questions (77+)

  Exceptions — Interview Questions (77+)

  @throws tags.

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• Exception hierarchy in Java?

  Exceptions — Interview Questions (77+)

  → (don't catch) and → checked vs (unchecked).

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• Exception chaining — why?

  Exceptions — Interview Questions (77+)

  Preserve root cause when wrapping at layer boundaries.

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• Custom exception design?

  Exceptions — Interview Questions (77+)

  Extend for checked, for unchecked; meaningful messages; optional error codes.

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• Should you catch `Exception` or `Throwable`?

  Exceptions — Interview Questions (77+)

  Avoid broad catch in application code; catch specific types.

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• Suppressed exceptions?

  Exceptions — Interview Questions (77+)

  Secondary exceptions during close/add suppressed to primary.

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• Assertions vs exceptions?

  Exceptions — Interview Questions (77+)

  for internal invariants (disabled by default); exceptions for contract violations callers should handle.

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• Best practices for exception messages?

  Exceptions — Interview Questions (77+)

  Actionable, include context (ids, operation), no secrets.

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• Generic exception?

  Generics — Interview Questions (60+)

  Use bounded wildcards on input params (PECS), exact types on outputs.

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• NotSerializableException?

  I/O, NIO & Serialization — Interview Questions (82+)

  Use virtual threads executor Java 21.

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• InaccessibleObjectException?

  Reflection & Annotations — Interview Questions (72+)

  Panama native interop.

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• Prefer standard exceptions?

  Effective Java & Best Practices — Interview Questions (82+)

  Named constants.

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• LazyInitializationException?

  Spring & Spring Boot — Interview Questions (92+)

  Complex bean creation.

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• SQLException checked?

  JDBC, JPA & Hibernate — Interview Questions (82+)

  Separate schema per tenant.

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Java versions

• Helpful NullPointerExceptions

  JEP 358 · Final

  Helpful NullPointerExceptions. A NullPointerException can name which part of an expression was null. The feature is on by default.

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