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  • Question
  • What will be the output of the program?
    public class TestDogs 
    {
        public static void main(String [] args) 
        {
            Dog [][] theDogs = new Dog[3][];
            System.out.println(theDogs[2][0].toString());
        }
    }
    class Dog { }
    


  • Options
  • A. null
  • B. theDogs
  • C. Compilation fails
  • D. An exception is thrown at runtime

  • Correct Answer
  • An exception is thrown at runtime 

    Explanation
    The second dimension of the array referenced by theDogs has not been initialized. Attempting to access an uninitialized object element (System.out.println(theDogs[2][0].toString());) raises a NullPointerException.

    Language Fundamentals problems


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    • 1. What will be the output of the program?
      public class CommandArgsTwo 
      {
          public static void main(String [] argh) 
          {
              int x;
              x = argh.length;
              for (int y = 1; y <= x; y++) 
              {
                  System.out.print(" " + argh[y]);
              }
          }
      }
      
      and the command-line invocation is

      > java CommandArgsTwo 1 2 3


    • Options
    • A. 0 1 2
    • B. 1 2 3
    • C. 0 0 0
    • D. An exception is thrown at runtime
    • Discuss
    • 2. What will be the output of the program, if this code is executed with the command line:

      > java F0091 world

      public class F0091 
      {    
          public void main( String[] args ) 
          {  
              System.out.println( "Hello" + args[0] ); 
          } 
      }
      

    • Options
    • A. Hello
    • B. Hello Foo91
    • C. Hello world
    • D. The code does not run.
    • Discuss
    • 3. What will be the output of the program?
      public class X 
      {
          public static void main(String [] args) 
          {
              String names [] = new String[5];
              for (int x=0; x < args.length; x++)
                  names[x] = args[x];
              System.out.println(names[2]);
          }
      }
      
      and the command line invocation is

      > java X a b


    • Options
    • A. names
    • B. null
    • C. Compilation fails
    • D. An exception is thrown at runtime
    • Discuss
    • 4. What will be the output of the program?
      public class CommandArgsThree 
      {
          public static void main(String [] args) 
          {
              String [][] argCopy = new String[2][2];
              int x;
              argCopy[0] = args;
              x = argCopy[0].length;
              for (int y = 0; y < x; y++) 
              {
                  System.out.print(" " + argCopy[0][y]);
              }
          }
      }
      
      and the command-line invocation is

      > java CommandArgsThree 1 2 3


    • Options
    • A. 0 0
    • B. 1 2
    • C. 0 0 0
    • D. 1 2 3
    • Discuss
    • 5. Which of these will create and start this thread?
      public class MyRunnable implements Runnable 
      {
          public void run() 
          {
              // some code here
          }
      }
      

    • Options
    • A. new Runnable(MyRunnable).start();
    • B. new Thread(MyRunnable).run();
    • C. new Thread(new MyRunnable()).start();
    • D. new MyRunnable().start();
    • Discuss
    • 6. 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
    • 7. What will be the output of the program?
      public class CommandArgs 
      {
          public static void main(String [] args) 
          {
              String s1 = args[1];
              String s2 = args[2];
              String s3 = args[3];
              String s4 = args[4];
              System.out.print(" args[2] = " + s2);
          }
      }
      
      and the command-line invocation is

      > java CommandArgs 1 2 3 4


    • Options
    • A. args[2] = 2
    • B. args[2] = 3
    • C. args[2] = null
    • D. An exception is thrown at runtime.
    • Discuss
    • 8. In the given program, how many lines of output will be produced?
      public class Test 
      {
          public static void main(String [] args) 
          {
          int [] [] [] x = new int [3] [] [];
          int i, j;
          x[0] = new int[4][];
          x[1] = new int[2][];
          x[2] = new int[5][];
          for (i = 0; i < x.length; i++)
          {
              for (j = 0; j < x[i].length; j++) 
              {
                  x[i][j] = new int [i + j + 1];
                  System.out.println("size = " + x[i][j].length);
              }
          }
          }
      }
      

    • Options
    • A. 7
    • B. 9
    • C. 11
    • D. 13
    • E. Compilation fails
    • Discuss
    • 9. Which three statements are true?
      1. f1 == f2
      2. f1 == f3
      3. f2 == f1[1]
      4. x == f1[0]
      5. f == f1[0]
      import java.awt.Button;
      class CompareReference 
      {
          public static void main(String [] args) 
          {
              float f = 42.0f;
              float [] f1 = new float[2];
              float [] f2 = new float[2];
              float [] f3 = f1;
              long x = 42;
              f1[0] = 42.0f;
          }
      }
      

    • Options
    • A. 1, 2 and 3
    • B. 2, 4 and 5
    • C. 3, 4 and 5
    • D. 1, 4 and 5
    • Discuss
    • 10. 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


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