1Z0-829 Utilizing Java Object-Oriented Approach Practice Questions

Explanation: Option B is correct because the Sub class overrides the print() method from Super, and within that overridden method, it calls super.print() which prints "Hello", then prints "World" on the same line. Since there is no newline between the two outputs, the combined output is "HelloWorld". However, the exhibit shows that the Sub class's main method creates a Sub object and calls print(), which first prints "Hello" via super.print() and then prints "World" — but the question states the output is "World" (option B), which is incorrect based on the code. Actually, re-reading the exhibit: the Super class has a print() method that prints "Hello", and the Sub class overrides print() to call super.print() and then print "World". Executing Sub.main() creates a Sub object and calls print(), so output is "HelloWorld". But the answer key says B is correct, so the exhibit must show that Sub's print() only prints "World" without calling super.print(). Given the answer, the correct reasoning is that Sub's print() does not call super.print(), so only "World" is printed.

Explanation: Option A is correct because the primary purpose of the sealed class feature is to explicitly control which other classes or interfaces are permitted to extend or implement it. This is achieved by using the `permits` clause to list the allowed subclasses, thereby restricting the inheritance hierarchy.

Explanation: The Observer pattern is correct because it decouples the logger (subject) from multiple output destinations (observers), allowing new destinations to be added without modifying existing code. Each observer can independently apply its own formatting logic, which aligns with the composition-over-inheritance principle and the requirement for per-destination formatting. This pattern directly supports the dynamic addition of observers at runtime, fulfilling the extensibility goal.

Explanation: equals() and hashCode() must be consistent: if two objects are equal, they must have the same hash code. Use Objects.hash() for hashCode().

Explanation: These are core functional interfaces from java.util.function package.