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Isn't there any way to find the class-type of a generic?
if (T instanceof String) { // do something... } The above definitely does not compile.
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Using generics to define the type in instanceofThe type used with instanceof has to be reifiable, which means that all information about the type has to be available at runtime, and this is usually not the case for generic types. Since types are gone, it's not possible for the JVM to know which type is T .
A type parameter, also known as a type variable, is an identifier that specifies a generic type name. The type parameters can be used to declare the return type and act as placeholders for the types of the arguments passed to the generic method, which are known as actual type arguments.
Generics add that type of safety feature. We will discuss that type of safety feature in later examples. Generics in Java are similar to templates in C++. For example, classes like HashSet, ArrayList, HashMap, etc., use generics very well.
Generics are a compile time feature. Generics add checks at compile time which may not have any meaning at runtime. This is one example. You can only check the type of the object referenced which could be a super type in code. If you want to pass the type T you have do this explicitly.
void someMethod(Class<T> tClass) { if(String.class.isAssignableFrom(tClass)) or
void someMethod(Class<T> tClass, T tArg) { Note: the type might not be the same,
someMethod(Number.class, 1); If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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