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Furthermore, methods or constructors with the same parameter types that differ only in their declaration order , are typically not flagged by Java compilers. This Errors can result in errors if a developer does not consult the documentation at every use of the method or constructor. A related pitfall is to associate differing different semantics with each of the overloaded methods or constructors. Defining different semantics sometimes necessitates different orderings of the same method parameters, creating a vicious circle. Consider, for example, a getDistance() method whose one overloading returns the distance traveled from the source while another (with rearranged parameters) returns the uncovered distance to the destination. An implementer may not realize the difference unless the documentation is consulted at every use.

Noncompliant Code Example (

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Constructor)

Constructors cannot be overridden and can only be overloaded. This noncompliant code example shows the constructor Con with three overloadings: Con(int, String), Con(String, int), and Con(Integer, String).

class Con {
  public Con(int i, String s) { /* Initialization Sequence #1 */ }
  public Con(String s, int i) { /* Initialization Sequence #2 */ } 
  public Con(Integer i, String s) { /* Initialization Sequence #3 */ } 
}

Failure to exercise caution while passing arguments to these constructors can create confusion as because these overloadings can contain the same number of similarly typed parameters. Overloading must also be avoided when the overloaded constructors or methods provide inconsistent functionality for arguments of the same types, differing just in their declaration order.

Compliant Solution (

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Constructor)

This compliant solution uses public static factory methods instead of public class constructors.

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In this noncompliant code example, the InformationLeak class holds a HashMap instance and returns a particular record to the caller based on the basis of either its key value in the map or the actual mapped value. The getData() method has been is overloaded to return the contained data indexed by the key value in the former case. In the latter case, it checks whether a particular record exists before formatting and returning it as a String object. The InformationLeak class inherits from java.util.HashMap and overrides its get() method to provide the checking functionality. This implementation can be extremely confusing to the client who will expect expects the getData() methods to behave in a similar fashion and not depend on whether an index of the record is specified or the value to be retrieved is specified.

A further problem is that , in the presence of autoboxing, an int argument may invoke the undesired overloading for Integer. This can happen if the overloading with the primitive int type is added to a class at a later date. Clients who expect the getData() method to fetch data based on the basis of its value will suddenly start invoking the new overloading whenever an int argument is passed and proceed to return the record by index. This happens because a primitive argument becomes more specific in the new version, whereas in the old one, autoboxing allows the selection of the method with the Integer type parameter when an int is passed.

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Although the client programmer might eventually deduce such behavior, other cases such as with the {{List}} interface may go unnoticed, as Bloch \[[Bloch 2008|AA. References#Bloch 08]\] describes:

... the The List<E> interface has two overloadings of the remove method: remove(E) and remove(int). Prior to release 1.5 when it was "generified," , the List interface had a remove(Object) method in place of remove(E), and the corresponding parameter types, Object and int, were radically different. But in the presence of generics and autoboxing, the two parameter types are no longer radically different.

Consequently, a client programmer may not realize that the wrong element has been removed from the list.

Compliant Solution (

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Method)

Naming the two related methods differently eliminates overloading.

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