logo

CuriousTab

CuriousTab

Discussion

Home ‣ Java Programming ‣ Declarations and Access Control See What Others Are Saying!
  • Question

  • Which two code fragments will compile?
    1. interface Base2 implements Base {}
    2. abstract class Class2 extends Base
      { public boolean m1(){ return true; }}
    3. abstract class Class2 implements Base {}
    4. abstract class Class2 implements Base
      { public boolean m1(){ return (7 > 4); }}
    5. abstract class Class2 implements Base
      { protected boolean m1(){ return (5 > 7) }}
    interface Base 
{
    boolean m1 ();
    byte m2(short s);
}


  • Options
  • A. 1 and 2
  • B. 2 and 3
  • C. 3 and 4
  • D. 1 and 5

  • Correct Answer
  • 3 and 4 

    Explanation
    (3) is correct because an abstract class doesn't have to implement any or all of its interface's methods. (4) is correct because the method is correctly implemented ((7 > 4) is a boolean).

    (1) is incorrect because interfaces don't implement anything. (2) is incorrect because classes don't extend interfaces. (5) is incorrect because interface methods are implicitly public, so the methods being implemented must be public.

    • More questions

    • 1. What will be the output of the program? 
      class Equals 
{
    public static void main(String [] args) 
    {
        int x = 100;
        double y = 100.1;
        boolean b = (x = y); /* Line 7 */
        System.out.println(b);
    }
}

    • Options
    • A. true
    • B. false
    • C. Compilation fails
    • D. An exception is thrown at runtime
      • Discuss
    • 2. Which interface does java.util.Hashtable implement?

    • Options
    • A. Java.util.Map
    • B. Java.util.List
    • C. Java.util.HashTable
    • D. Java.util.Collection
      • Discuss
    • 3. Which two of the following methods are defined in class Thread?

      1. start()
      2. wait()
      3. notify()
      4. run()
      5. terminate()

    • Options
    • A. 1 and 4
    • B. 2 and 3
    • C. 3 and 4
    • D. 2 and 4
      • Discuss
    • 4. What will be the output of the program? 
      class MyThread extends Thread 
{
    public static void main(String [] args) 
    {
        MyThread t = new MyThread(); /* Line 5 */
        t.run();  /* Line 6 */
    }

    public void run() 
    {
        for(int i=1; i < 3; ++i) 
        {
            System.out.print(i + "..");
        }
    }
}

    • Options
    • A. This code will not compile due to line 5.
    • B. This code will not compile due to line 6.
    • C. 1..2..
    • D. 1..2..3..
      • Discuss
    • 5. What will be the output of the program? 
      class MyThread extends Thread 
{
    MyThread() 
    {
        System.out.print(" MyThread");
    }
    public void run() 
    {
        System.out.print(" bar");
    }
    public void run(String s) 
    {
        System.out.println(" baz");
    }
}
public class TestThreads 
{
    public static void main (String [] args) 
    {
        Thread t = new MyThread() 
        {
            public void run() 
            {
                System.out.println(" foo");
            }
        };
        t.start();
    }
}

    • Options
    • A. foo
    • B. MyThread foo
    • C. MyThread bar
    • D. foo bar
      • Discuss
    • 6. What will be the output of the program? 
      String s = "hello"; 
Object o = s; 
if( o.equals(s) )
{
    System.out.println("A"); 
} 
else
{
    System.out.println("B"); 
} 
if( s.equals(o) )
{
    System.out.println("C"); 
} 
else
{ 
    System.out.println("D"); 
}
      1. A
      2. B
      3. C
      4. D

    • Options
    • A. 1 and 3
    • B. 2 and 4
    • C. 3 and 4
    • D. 1 and 2
      • Discuss
    • 7. Which class or interface defines the wait(), notify(),and notifyAll() methods?

    • Options
    • A. Object
    • B. Thread
    • C. Runnable
    • D. Class
      • Discuss
    • 8. What will be the output of the program? 
      public class Test 
{
    public static void main(String [] args) 
    {
        signed int x = 10;
        for (int y=0; y<5; y++, x--)
            System.out.print(x + ", ");
    }
}

    • Options
    • A. 10, 9, 8, 7, 6,
    • B. 9, 8, 7, 6, 5,
    • C. Compilation fails.
    • D. An exception is thrown at runtime.
      • Discuss
    • 9. Which two of the following statements, inserted independently, could legally be inserted into missing section of this code?
      1. boolean test = (Component instanceof t);
      2. boolean test = (t instanceof Ticker);
      3. boolean test = t.instanceof(Ticker);
      4. boolean test = (t instanceof Component);
          
import java.awt.*;
class Ticker extends Component 
{
    public static void main (String [] args) 
    {
        Ticker t = new Ticker();
        /* Missing Statements? */
    }
}

    • Options
    • A. 1 and 4
    • B. 2 and 3
    • C. 1 and 3
    • D. 2 and 4
      • Discuss
    • 10. What will be the output of the program? 
      class Test 
{
    public static void main(String [] args) 
    {
        int x=20;
        String sup = (x < 15)? "small" : (x < 22)? "tiny" : "huge";
        System.out.println(sup);
    }
}

    • Options
    • A. small
    • B. tiny
    • C. huge
    • D. Compilation fails
      • Discuss

    Comments

    There are no comments.
Enter a new Comment




Aptitude

Engineering

Programming

Reasoning

Links

Copyright ©CuriousTab. All rights reserved.