Item 27: Favor generic methods

1.  Generic methods, like generic types, are safer and easier to use than methods that require their clients to cast input parameters and return values. 

 

2.  The type parameter list, which declares the type parameter, goes between the method’s modifiers and its return type.

 

3.  One noteworthy feature of generic methods is that you needn’t specify the value of the type parameter explicitly as you must when invoking generic constructors. The compiler figures out the value of the type parameters by examining the types of the method arguments. This process is called type inference.

 

4.  On occasion, you will need to create an object that is immutable but applicable to many different types. This pattern is called generic singleton factory which is most frequently used for function objects such as Collections.reverseOrder, but it is also used for collections such as Collections.emptySet.

 

5.  It is permissible, though relatively rare, for a type parameter to be bounded by some expression involving that type parameter itself. This is what’s known as a recursive type bound:

// Using a recursive type bound to express mutual comparability
public static <T extends Comparable<T>> T max(List<T> list) {...}