What are common mistakes developers make with generic type bounds?

When working with generics in Java, developers often encounter several common mistakes related to type bounds. Understanding how to properly use generic type bounds can enhance code quality, improve type safety, and prevent runtime errors.

Common Mistakes with Generic Type Bounds

  • Not using wildcard types when appropriate.
  • Confusing extends and super bounds.
  • Using raw types instead of parameterized types.
  • Inconsistent type parameters in class and method definitions.
  • Misunderstanding type erasure.

Example

<![CDATA[ // Example demonstrating the misuse of bounds public class Box { private T item; public void setItem(T item) { this.item = item; } public T getItem() { return item; } } // Incorrect usage with raw type Box rawBox = new Box(); // This eliminates type safety // Correct usage with type parameter Box stringBox = new Box<>(); stringBox.setItem("Hello"); System.out.println(stringBox.getItem()); ]]>

generic types java generics type bounds wildcards type safety

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