Generics In Java — Part 2 MCQs with Explanations

1 is the correct answer to “What will be the output of the following Java program? import java.util.*; class Output { public static void addNumbers(List<? super Integer> list) { for (int i = 1; i <= 10; i++) { list.add(i); } } public static void main(String args[]) { List<Double> ld = Arrays.asList(); addnumbers(10.4); System.out.println("getList(2)"); } }”. This question is standard in competitive examination syllabi for Generics In Java.

List<? extends Number> is the correct answer to “Which of these is an correct way making a list that is upper bounded by class Number”. This question is standard in competitive examination syllabi for Generics In Java.

Box #0 contains [10] is the correct answer to “What will be the output of the following Java program? public class BoxDemo { public static <U> void addBox(U u, java.util.List<Box<U>> boxes) { Box<U> box = new Box<>(); box.set(u); boxes.add(box); } public static <U> void outputBoxes(java.util.List<Box<U>> boxes) { int counter = 0; for (Box<U> box: boxes) { U boxContents = box.get(); System.out.println("Box #" + counter + " contains [" + boxContents.toString() + "]"); counter++; } } public static void main(String[] args) { java.util.ArrayList<Box<Integer>> listOfIntegerBoxes = new java.util.ArrayList<>(); BoxDemo.<Integer>addBox(Integer.valueOf(10), listOfIntegerBoxes); BoxDemo.outputBoxes(listOfIntegerBoxes); } }”. This question is standard in competitive examination syllabi for Generics In Java.

N is the correct answer to “Which of these type parameters is used for a generic methods to return and accept a number”. This question is standard in competitive examination syllabi for Generics In Java.

Type Interface is the correct answer to “Which of the following allows us to call generic methods as a normal method”. This question is standard in competitive examination syllabi for Generics In Java.

Hello is the correct answer to “What will be the output of the following Java program? import java.util.*; public class genericstack <E> { Stack stk = new Stack <E>(); public void push(E obj) { stk.push(obj); } public E pop() { E obj = stk.pop(); return obj; } } class Output { public static void main(String args[]) { genericstack <String> gs = new genericstack (); gs.push("Hello"); System.out.println(gs.pop()); } }”. This question is standard in competitive examination syllabi for Generics In Java.

T is the correct answer to “Which of these type parameters is used for a generic methods to return and accept any type of object”. This question is standard in competitive examination syllabi for Generics In Java.

super is the correct answer to “Which of the following keywords are used for lower bounding a wild card”. This question is standard in competitive examination syllabi for Generics In Java.

It is used in cases when type being operated upon is not known is the correct answer to “What is use of wildcards”. This question is standard in competitive examination syllabi for Generics In Java.

Primitive Types is the correct answer to “Which of these types cannot be used to initiate a generic type”. This question is standard in competitive examination syllabi for Generics In Java.