Which keyword is used to declare a generic class in Java?
Q.3Easy
What will be the output of the following code?
List<String> list = new ArrayList<>();
list.add("Java");
System.out.println(list.get(0).length());
Q.4Easy
Which of the following is a valid generic method declaration?
Q.5Medium
What is type erasure in Java Generics?
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Q.6Medium
Which statement about wildcard generics (?) is correct?
Q.7Medium
What will happen when you try to create an array of generics?
List<String>[] array = new List<String>[10];
Q.8Medium
Consider the code:
List<? extends Number> list = new ArrayList<>();
list.add(5); // Will this compile?
Q.9Medium
Which of the following represents a bounded type parameter?
Q.10Medium
What is the difference between List<?> and List<Object>?
Q.11Medium
Consider this generic interface:
interface Comparable<T> { int compareTo(T o); }
Which class definition correctly implements this?
Q.12Medium
What will be the output?
List<Integer> list = new ArrayList<>();
list.add(10);
Object obj = list.get(0);
System.out.println(obj instanceof Integer);
Q.13Hard
Which of these correctly demonstrates the Producer Extends Consumer Super (PECS) principle?
Q.14Hard
What will happen with this code?
List list = new ArrayList<String>();
list.add(123); // Adding Integer
String s = (String) list.get(0);
Q.15Hard
Consider this code:
public <T extends Comparable<T>> T getMax(T a, T b) {
return a.compareTo(b) > 0 ? a : b;
}
What is the benefit of this recursive bound <T extends Comparable<T>>?
Q.16Easy
What is the output of this generic code?
class Pair<K, V> {
public void display(K key, V value) {
System.out.println(key + ": " + value);
}
}
Pair<String, Integer> p = new Pair<>();
p.display("Age", 25);
Q.17Hard
Which statement is true about generic inheritance?
Q.18Hard
What will be the result of this code?
List<String> list = new ArrayList<>();
list.add("Hello");
List raw = list; // Unchecked assignment
raw.add(123); // Adding Integer to raw type
String s = list.get(1);
Q.19Medium
Which of these declarations would NOT cause a compilation warning or error?
Q.20Easy
In Java generics, what does the wildcard '?' represent?
