1z0-830 Exam Dumps : Java SE 21 Developer Professional

In Java generics, wildcards are used to relax the type constraints of generic types. The extends wildcard () denotes an upper bounded wildcard, allowing any type that is a subclass of Type. Conversely, the super wildcard () denotes a lower bounded wildcard, allowing any type that is a superclass of Type.

Option A:

java

public List getListSuper() {

return new ArrayList();

}

Here, List represents a list that can hold IOException objects and objects of its supertypes. Since Exception is a superclass of IOException, ArrayList is compatible with List. Therefore, this method compiles successfully.

Option B:

java

public List getListExtends() {

return new ArrayList();

}

In this case, List represents a list that can hold objects of IOException and its subclasses. Since FileNotFoundException is a subclass of IOException, ArrayList is compatible with List. Thus, this method compiles successfully.

Option C:

java

public List getListExtends() {

return new ArrayList();

}

Here, List expects a list of IOException or its subclasses. However, Exception is a superclass of IOException, not a subclass. Therefore, ArrayList is not compatible with List, and this method will not compile.

Option D:

java

public List getListSuper() {

return new ArrayList();

}

In this scenario, List expects a list that can hold IOException objects and objects of its supertypes. Since FileNotFoundException is a subclass of IOException, ArrayList is not compatible with List, and this method will not compile.

Therefore, the methods in options A and B compile successfully, while those in options C and D do not.

In this code, a double variable amount is initialized to 42,000.00. The NumberFormat.getCompactNumberInstance(Locale.FRANCE, NumberFormat.Style.SHORT) method is used to obtain a compact number formatter for the French locale with the short style. The format method is then called to format the amount.

The compact number formatting is designed to represent numbers in a shorter form, based on the patterns provided for a given locale. In the French locale, the short style represents thousands with a lowercase 'k'. Therefore, 42,000 is formatted as 42 k.

Option Evaluations:

A. 42000E: This format is not standard in the French locale for compact number formatting.

B. 42 000,00 €: This represents the number as a currency with two decimal places, which is not the compact form.

C. 42000: This is the plain number without any formatting, which does not match the compact number format.

D. 42 k: This is the correct compact representation of 42,000 in the French locale with the short style.

Thus, option D (42 k) is the correct output.

In this code, the SmartPhone interface declares a method ring() with a boolean return type. The Iphone15 class implements the SmartPhone interface and provides an implementation for the ring() method.

However, in the Iphone15 class, the ring() method is declared without the public access modifier. In Java, when a class implements an interface, it must provide implementations for all the interface's methods with the same or a more accessible access level. Since interface methods are implicitly public, the implementing methods in the class must also be public. Failing to do so results in a compilation error.

Therefore, the Iphone15 class does not compile because the ring() method is not declared as public.