Checked or Unchecked Exceptions in Java: When Should You Choose Which?

When Should You Opt for Checked or Unchecked Exceptions?

When defining custom exception classes in Java, developers grapple with the choice between checked and unchecked exceptions. To discern the appropriate classification, consider the following guidelines:

Use Checked Exceptions When:

• Predictable but Unpreventable Errors: Specify a checked exception when the underlying error can be reasonably anticipated but lies beyond the purview of the caller's control. For example, if a file read operation fails due to its deletion during execution, a checked exception aptly informs the caller of this predictable yet inevitable error.
• Reasonable to Recover From: Opt for a checked exception only if the error allows for meaningful recovery by the caller. If a user attempts to access a non-existent file, the caller can prompt the user for an alternative path, demonstrating the feasibility of recovery from this predictable error.

Use Unchecked Exceptions For:

• All Other Exceptional Conditions: In all scenarios that do not meet the criteria for checked exceptions, default to unchecked exceptions. This includes situations where the error is unpredictable, preventable, or unrecoverable.

Re-evaluating at Different Levels:

The appropriateness of an exception classification might vary at different levels of a program. If the exception is caught at an unsuitable level, consider the following:

• Wrap Checked Exceptions in Unchecked Exceptions: If a checked exception cannot be handled at the current level, convert it to an unchecked exception to propagate it further.
• Convert Unchecked Exceptions to Checked Exceptions: Conversely, if an unchecked exception is encountered at a level where it warrants handling, re-throw it as a checked exception to enforce anticipation of the predictable error.

Maintaining Adequate Abstraction:

For both checked and unchecked exceptions, employ the appropriate level of abstraction. Avoid exposing implementation-specific details by using generic exception classes that encapsulate the underlying implementation. For instance, in a code repository, a RepositoryException would be more suitable to generalize exceptions from database or filesystem implementations.

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