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Home Java Programming Declarations and Access Control See What Others Are Saying!
  • Question
  • Which three are valid method signatures in an interface?

    1. private int getArea();
    2. public float getVol(float x);
    3. public void main(String [] args);
    4. public static void main(String [] args);
    5. boolean setFlag(Boolean [] test);


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

  • Correct Answer
  • 2, 3 and 5 

    Explanation
    (2), (3), and (5). These are all valid interface method signatures.

    (1), is incorrect because an interface method must be public; if it is not explicitly declared public it will be made public implicitly. (4) is incorrect because interface methods cannot be static.


    More questions

    • 1. 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
    • 2. 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
    • 3. 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
    • 4. Which statement, inserted at line 10, creates an instance of Bar?
      class Foo 
      {
          class Bar{ }
      }
      class Test 
      {
          public static void main (String [] args) 
          {
              Foo f = new Foo();
              /* Line 10: Missing statement? */
          }
      }
      

    • Options
    • A. Foo.Bar b = new Foo.Bar();
    • B. Foo.Bar b = f.new Bar();
    • C. Bar b = new f.Bar();
    • D. Bar b = f.new Bar();
    • Discuss
    • 5. What line of code should replace the missing statement to make this program compile?
      /* Missing Statement? */
      public class foo 
      {
          public static void main(String[]args)throws Exception 
          {
              java.io.PrintWriter out = new java.io.PrintWriter(); 
              new java.io.OutputStreamWriter(System.out,true); 
              out.println("Hello"); 
          } 
      }
      

    • Options
    • A. No statement required.
    • B. import java.io.*;
    • C. include java.io.*;
    • D. import java.io.PrintWriter;
    • Discuss
    • 6. When is the B object, created in line 3, eligible for garbage collection?
      void start() {  
          A a = new A(); 
          B b = new B(); 
          a.s(b);  
          b = null; /* Line 5 */
          a = null;  /* Line 6 */
          System.out.println("start completed"); /* Line 7 */
      } 
      

    • Options
    • A. after line 5
    • B. after line 6
    • C. after line 7
    • D. There is no way to be absolutely certain.
    • Discuss
    • 7. Which is a reserved word in the Java programming language?

    • Options
    • A. method
    • B. native
    • C. subclasses
    • D. reference
    • E. array
    • Discuss
    • 8. Which statement is true for the class java.util.ArrayList?

    • Options
    • A. The elements in the collection are ordered.
    • B. The collection is guaranteed to be immutable.
    • C. The elements in the collection are guaranteed to be unique.
    • D. The elements in the collection are accessed using a unique key.
    • Discuss
    • 9. What will be the output of the program?
      public class Test 
      { 
          public static void main(String[] args) 
          {
              final StringBuffer a = new StringBuffer(); 
              final StringBuffer b = new StringBuffer(); 
      
              new Thread() 
              { 
                  public void run() 
                  {
                      System.out.print(a.append("A")); 
                      synchronized(b) 
                      { 
                          System.out.print(b.append("B")); 
                      } 
                  } 
              }.start(); 
                  
              new Thread() 
              {
                  public void run() 
                  {
                      System.out.print(b.append("C")); 
                      synchronized(a) 
                      {
                          System.out.print(a.append("D")); 
                      } 
                  } 
              }.start(); 
          } 
      }
      

    • Options
    • A. ACCBAD
    • B. ABBCAD
    • C. CDDACB
    • D. Indeterminate output
    • Discuss
    • 10. Which is true about a method-local inner class?

    • Options
    • A. It must be marked final.
    • B. It can be marked abstract.
    • C. It can be marked public.
    • D. It can be marked static.
    • Discuss


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