Reading Type From UpperBound

Java-Reading Type From UpperBound

Reading Type From UpperBound We have to take the two cases separately. Drawing on the analogy of a container, we’ll call getting a return value from a method on an object as a specific type reading the object as a type. Conversely, we’ll call passing arguments of a specific type to methods of the object … Read more…

Bounded Wildcards

Java-Bounded Wildcards

Bounded Wildcards A bounded wildcard is a wildcard that uses the extends keyword just as a type variable would to limit the range of assignable types. For example : Our ‘abc’ variable is limited to holding instantiations of Gen on parameter types of A and its subclasses(B and C). So, we can assign it a Gen<A> or … Read more…

Wildcard Arguments

Java-Wildcard Arguments

Wildcard Arguments There are two types of generic instantiation : concrete type instantiations and wildcard instantiations. Concrete type instantiations parameter arguments are real Java types. For example : Gen<Integer> and Gen<Double> are instantiations of the generic Gen class with the concrete types Integer and Double. Another kind of generic type instantiation is wildcard instantiation. Wildcards are … Read more…

Bounded Types

Java-Bounded Types

Bounded Types In some situations you define a generic type where you want to constrain the type arguments that are supplied to define a class instance so that they extend a particular class, or implement specific interfaces, or even both. The reason for this is that your generic type has to make some assumptions about … Read more…

Generic Arrays

Java-Generic Arrays

Generic Arrays It’s also possible to create generic arrays. There are two important generics restrictions that apply to arrays. First, you cannot instantiate an array whose element type is a type parameter. Second, you cannot create an array of type-specific generic references. Following class shows, it’s valid to declare a reference to an array of type T, T … Read more…

Type Inference

Java-Type Inference

Type Inference One noteworthy JDK 7 feature 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 constructor arguments. This process is called type inference. For example, consider the following generic class and its instances : … Read more…