Inheritance of Wildcards

Java-Inheritance of Wildcards

Inheritance of Wildcards If we have two different wildcard instantiations of a type or related types, how, if at all, are they related? For example, can an unbounded wildcard be assigned a value with a more restrictive bound because it can hold any instantiation? The answer is yes. For example: For purposes of assignability, wildcard … Read more…

Difference Between Unbounded Wildcard, Raw Type and

Java-Difference Between Unbounded Wildcard, Raw Type and Object

Difference Between Unbounded Wildcard, Raw Type and Object Natural questions to ask are, What good is the unbounded wildcard anyway? Why not just use the raw type? How do unbounded wildcard instantiation and raw types compare? The first difference is that the compiler will issue unchecked warnings when we use methods of the raw type. … Read more…

Array of Wildcards

Java-Array of Wildcards

Array of Wildcards In general, wildcard instantiations of generics can be used as the base type for arrays in the same way that concrete instantiations can. For example: The first statement declares an array of unbounded wildcard instantiations of Gen. Each element of the array can hold an instance of the wildcard type, meaning in this … Read more…

Arrays of Parameterized Types

Java-Arrays of Parameterized Types

Arrays of Parameterized Types You cannot create an array of type-specific generic references. Attempting to create an array of type-specific generic, causes a compiler error.  For example, the following statement is not permitted and results in a compiler error message: This code is the simplest approach to creating an array of a generic type and the … Read more…

Wildcard Capture

Java-Wildcard Capture

Wildcard Capture  Generic methods can do one more trick for us involving taming wildcard instantiations of generic types. The term wildcard capture refers to the fact that generic methods can work with arguments whose type is a wildcard instantiation of a type, just as if the type were known. For example, consider the following classes, … Read more…

Generic Method with Lower Bound

Java-Generic Method with Lower Bound

Generic Method with Lower Bound Lower bounds are useful for cases where we want to be sure that a particular container instantiation can hold a particular element type, without limiting it to just the specific type of the element. For example, consider the following generic method: Note that T extends Comparable<T>. The Comparable is an generic interface declared … Read more…