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 program shows, it’s valid to declare a reference to an array of type T, … Read more…

Constructor Reference for Array

Java-Constructor Reference for Arrays

Constructor Reference for Arrays Another form of the constructor reference syntax that is used for arrays. To create a constructor reference for an array, use the construct : type[ ]::new. Type specifies the type of object being created. For example, the following creates a three-element array of MyClass objects and gives each element an initial … Read more…

Constructor References

Java-Constructor References

Constructor References It is also possible to create references to constructors. This is the general form of the syntax that you will use : className::new. This reference can be assigned to any functional interface reference that defines a method compatible with the constructor. For example, in the following program, the MyMethod( ) method of MyInterface returns a reference of … Read more…

Method References to Generics

Java-Method References to Generics

Method References to Generics You can use method references with generic classes and/or generic methods. For example, in the following program, MyClass is a non-generic class that contains a static generic method called showData( ). This method print the elements in an specified array. Notice how the generic type argument is specified. For example, its first call … Read more…