Java MCQ – Generic types

This collection of Java Multiple Choice Questions and Answers (MCQs): Quizzes & Practice Tests with Answer focuses on “Generic types”.
 

1. What is the purpose of Generic types in Java?

A It makes the code faster

B It makes the code more optimized and more readable

C It adds stability to your code by making your bugs detectable at runtime

D It adds stability to your code by making your bugs detectable at compile time

2. Which of these type of parameters is used for a generic class to return and accept any type of object?

A V

B T

C N

D K

3. Which of these type parameters is used for a generic class to return and accept a number?

A V

B T

C N

D K

4. Which of the following types of reference cannot be generic?

A Inner classes

B Interface

C Inner class anonymous

D All the answers are true

5. Which of the following statements is incorrect about the use of generic and parameterized types in Java?

A When designing your own class of collections, generic and parameterized types allow you to achieve type security with a single class definition rather than defining multiple classes

B Generic and parameterized types removes the need for top-down conversions when using Java collections

C Generic type in Java ensures type safety by transferring type checking responsibilities to the compiler

D All the answers are true

6. Which of the following methods is correct for defining a generic class?

A class MyClass2 <T1, T2, ....., Tn> { /* … */ }

B class MyClass4 {T1, T2, …, Tn} { /* … */ }

C class MyClass3 [T1, T2, …, Tn] { /* … */ }

D class MyClass1(T1, T2, …, Tn) { /* … */ }

7. What is the output of this program?

import java.util.*;

class GenericStack <E>
{
      Stack <E> stack = new Stack <E>();
      
      public E pop()
      {
          E obj = stack.pop();
          return obj;
      }
      public void push(E obj) 
      {
         stack.push(obj);
      }
}
public class Test
{
     public static void main(String args[])
     {
         GenericStack <String> gs = new GenericStack <String>();
         gs.push("Hello");
         System.out.println(gs.pop());
     }
}

A Hello

B Compilation error

C obj478962

D 44

	
$ javac Test.javac
$ java Test
Hello

8. What is the output of this program?

import java.util.*;

class GenericStack <E> 
{
     Stack <E> stack = new Stack <E>();
     public E pop()
     {
          E obj = stack.pop();
          return obj;
     }
     public void push(E obj)
     {
         stack.push(obj);
     }
}

public class Test
{
     public static void main(String args[])
     {
         GenericStack <Integer> gs = new GenericStack <Integer>();
         gs.push(44);
         System.out.println(gs.pop());
     }
}

A Compilation error

B Runtime error

C obj478962

D 44

	
$ javac Test.javac
$ java Test
44

9. What is the output of this program?

import java.util.*;


class GenericStack <E>
{
    Stack <E> stack = new Stack <E>();
    public void push(E obj)
    {
         stack.push(obj);
    }
    public E pop()
    {
         E obj = stack.pop();
         return obj;
    }
}

public class Test
{
    public static void main(String args[])
    {
         GenericStack <String> gs = new GenericStack <String>();
         gs.push("Hello");
         System.out.print(gs.pop() + " ");
         GenericStack <Integer> gs  = new GenericStack <Integer>();
         gs.push(44);
         System.out.println(gs.pop());
     }
}

A Hello 44

B Compilation error

C Hello

D 44

$ javac Test.javac
$ java Test
error: incompatible types: int cannot be converted to String

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