Item Use overload judiciously

Overload problem:

• Method overloading, as in the example of the CollectionClassifier program, can lead to unexpected behavior, as the selection of which method to invoke occurs at compile time, based on the parameter type, and not at run time.

Overload vs Overwrite:

• While overloading chooses the method at compile time, overriding chooses the correct method based on the type at runtime, which makes the behavior more predictable.

Avoid confusing overhead:

• Overloading can confuse programmers when it is not clear which method will be invoked for a set of parameters. This is especially problematic in public APIs.

Recommendations:

• Avoid exporting two overloads with the same number of parameters.
• Name methods differently instead of overloading (like writeInt and writeBoolean).
• When using varargs, avoid overloading.

Case of generics and autoboxing:

• The introduction of generics and autoboxing in Java has led to overloading problems, as shown in the example of List.remove, which can behave confusingly due to the presence of multiple overloads.

Functional interfaces and lambdas:

• The addition of lambdas in Java 8 increased the risk of confusion by overloading methods that take functional interfaces, especially when those interfaces are not "radically different".

Practical solutions:

• Explicit testing with instanceof can avoid the problems associated with overloading.
• Overloads with radically different parameters (types that cannot be converted to each other) avoid confusion.
• Constructors and overloading: Although constructors are always overloaded, using static factories can avoid some of this complexity.

Justified exceptions:

• In some cases, such as adapting old classes, overloading may be necessary, but it must be used carefully, ensuring that overloaded methods behave identically when invoked with the same parameters.

Conclusion:

• Overloads should be used sparingly. Although technically possible, it is often preferable to name methods differently or avoid confusing overloads to ensure clearer, more predictable code.

Examples from the book:

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