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Do not introduce ambiguity while overloading (see 71. MET50-JG. Avoid ambiguous or confusing uses of overloading), and use overloaded methods sparingly [Tutorials 2008], because they can make code much less readable.
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This noncompliant code example attempts to use the overloaded display() method to perform different actions depending on whether the method is passed an ArrayList<Integer> or a LinkedList<String>.:
| Code Block | ||
|---|---|---|
| ||
public class Overloader {
private static String display(ArrayList<Integer> arrayList) {
return "ArrayList";
}
private static String display(LinkedList<String> linkedList) {
return "LinkedList";
}
private static String display(List<?> list) {
return "List is not recognized";
}
public static void main(String[] args) {
// Single ArrayList
System.out.println(display(new ArrayList<Integer>()));
// Array of lists
List<?>[] invokeAll = new List<?>[] {new ArrayList<Integer>(),
new LinkedList<String>(), new Vector<Integer>()};
for (List<?> list : invokeAll) {
System.out.println(display(list));
}
}
}
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This compliant solution uses a single display method and instanceof to distinguish between different types. As expected, the output is ArrayList, ArrayList, LinkedList, List is not recognized.:
| Code Block | ||
|---|---|---|
| ||
class Overloader {
public class Overloader {
private static String display(List<?> list) {
return (
list instanceof ArrayList ? "Arraylist" :
(list instanceof LinkedList ? "LinkedList" :
"List is not recognized")
);
}
public static void main(String[] args) {
// Single ArrayList
System.out.println(display(new ArrayList<Integer>()));
List<?>[] invokeAll = new List<?>[] {new ArrayList<Integer>(),
new LinkedList<String>(), new Vector<Integer>()};
for (List<?> list : invokeAll) {
System.out.println(display(list));
}
}
}
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