What is the contract between `hashCode()` and `equals()` for objects used as `HashMap` keys?

Java Professional Medium

Java Professional — Medium

What is the contract between `hashCode()` and `equals()` for objects used as `HashMap` keys?

Key points

  • `hashCode()` and `equals()` must be consistent for objects used as HashMap keys
  • Equal objects should have the same hashCode to ensure proper key retrieval
  • Unequal objects can have different hashCodes for efficiency
  • This contract is crucial for HashMap performance

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