The interfaces of the Java Collections Framework [JCF 2014] use generically typed, parameterized methods, such as add(E e) and put(K key, V value), to insert objects into the collection or map, but they have other methods, such as contains(), remove(), or get(), that accept an argument of type Object rather than a parameterized type. Consequently, this these methods accept an object of any type. The collections framework interfaces were designed in this manner to maximize backwards compatibility, but this design can also lead to coding errors. Programmers must ensure that arguments passed to methods such as Map<K,V> get(), Collection<E> contains(), and remove() have the same type as the parameterized type of the corresponding class instance.
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| [JCF 2014] | The Java Collections Framework |
Chapter 5 | |
[JLS 2005] | |
The Joy of Sets |
02. Expressions (EXP) EXP05-J. Do not write more than once to the same variable within an expression