SCJP2 Practice Exam 1
   Copyright (c) 2002 Rajinder Yadav

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   thank you.

   You may send your comments, suggestions and corrections to:

   Rajinder Yadav
   email: rajindery@yahoo.com



1) If you try to compile the following program and run it, what will happen?

public class Test extends Thread {
   static final byte LIMIT = 255;  //line 1
   static String msg;
   
   Test(String s) {
      msg = s;
   }
   
   public static void main(String noway[]) { //line 2
      Test t = new Test("Hello!");
      t.run();  // line 3
   }
   
   public void run() {
      
      for(int i=0; i<LIMIT; ++i) { // line 4
         System.out.println(msg);
      }
   }
}

a will not compile because of line 1
b will output 255 strings of "Hello!"
c method main() is incorrect on line 2
d can mix int and byte types in loop on line 4
e need to call the thread's start() method on line 3


2) Which of the following are not valid java keywords

   a) public
   b) default
   c) native
   d) const
   e) do
   

3) If a class Worker extends the class Thread, and the Worker class overrides 
   the run() method to list the files in the current directory. Which of the 
   following statements will cause a directory to be displayed?

   a) Worker w = new Worker();
      w.run();
      
   b) new Worker().run();
      
   c) Thread t = new Thread(new Worker());
      t.run();
      
   d) new Thread(new Worker()).start();


4) what will happend if you try to compile and run the following program?

public class Test extends Thread {
  
   public static void main(String[] args) {
      Worker w = new Worker();
      w.start();      
   }
}

Worker extends Thread {   
   public void run() {
      for(int i=0; i<2; ++i) {
         for(int j=0; j=<2; ++j) {
            System.out.println("Directory");
         } 
      } 
   }
}

a will out "Directory" 2 times
b will out "Directory" 3 times
c will out "Directory" 6 times
d will not compile


5) which of the following are valid array initialization;

   a) int i[5] = {1,2,3,4,5};
      
   b) int [][]j = new int[3][4];
      
   c) int j[] = new[5];
      
   d) int[] k[]= {{1,2}, {3,3,3}, {1}};
      
   e) Object o[] = new Object[]{new Object(), new Object()};
   

6) what will be the value of j if this program is compiled and 
   run using, 'java Test 12 7 6'

public class Test extends Thread  {
     
   public static void main(String[] args) {
      final byte n=7;
      int j=0;
      
      int i = new Integer(args[2]).intValue();      
     
      switch(i) {
         default:
            j=12;
            break;
         case 6:
            j=-9;
         case n:
            j=++j;
         break;
      }
      System.out.println(j);
   }
}

   a) j = 12
   b) j = -9
   c) j = 1
   d) j = -8
   e) will not compile
   
               
7) given the following statements, what will be the outcome?

   boolean b = false;
   int i = 10;
   int j = 10;
   b = (b=j==i)?true:false;

   a) b will be true
   b) b will be false
   c) these statements would not compile


8) given the following statements, what will be the outcome?

public class Test extends Thread  {  
   
   public static void main(String[] args) {
      boolean b = true;
      int i = 10;
      int j = 12;
      
      if((i == 12) && (b = false)) {
         System.out.println("Yes");
      }      
         System.out.println(b);
   }
}

   a) will output "Yes" and 'true'
   b) will output "Yes" and 'false'
   c) will output 'true'
   d) will output 'false'


9) given the following statements, what will be the outcome?

public static void main(String[] args) {
      boolean b = true;
      int i = 10;
      int j = 12;
      
      if((i == 12) || (b = false)) {
         System.out.println("Yes");
      }      
      System.out.println(b);
   }
}

   a) will outout "Yes" and 'true'
   b) will output "Yes" and 'false'
   c) will output 'true'
   d) will output 'false'
   

10) When is the earliest that the string "Trash" become eligible 
    for garbage collection?

public class Test extends Thread  {     

   public static void main(String[] args) {
      String cleanup = new String("Trash");
      doIt(cleanup);
      cleanup = null; // line 1
    }                 // line 2
    
    static void doIt(String s) {
       s = null; // line 3
    }
} // line 4

   a) after line 1
   b) after line 2
   c) after line 3
   d) after line 4


11) when this program is run, what letters get displayed?

public class Test extends Thread  {        

   public static void main(String[] args) {
      try {
         try {
            int i=5/0;
            System.out.println("A");
         }
         finally {
           System.out.println("B");
         }
         System.out.println("X");
       }
       catch(Exception e) {
          System.out.println("Y");
       }
       System.out.println("Q");
    }
}

   a) B,X,Y
   b) B,Y,Q
   c) B,X,Y,Q
   d) A,B,X,Q
   

12) Given the following class hierarchy, which assignments are valid?
   
   interface I {}
   class A {}
   class B implements I {}
   class D extends B {}
   
   A a = new A();
   B b = new B();
   D d = new D();
   
   a) I i = d;   
   b) Object o = a;
   c) D d1 = b;
   d) B b1 = d;
   e) A a1 = (A)b;


13) How many object are eligible for garbage collection after // line 1

public class Test extends Thread  {        

   public static void main(String[] args) {
      Object o1 = new Object();
      Object o2 = new Object();
      Object o3 = new Object();
      
      doIt(o1, o2, o3);      
   }
    
    static void doIt(Object o1, Object o2, Object o3) {
       o1 = o2 = o3; // line 1
    }
}
   a) zero
   b) three
   c) one
   d) two
   

14) What will get displayed by the following statements?

   System.out.println(Math.round(Double.NaN));
   System.out.println(Math.abs(-0.0));
   System.out.println(Math.ceil(-0.8));
   
   a) NaN
     -0.0
     -1.0
     
   b) 0
     -0.0
     -0.0
   
   c) 0
      0.0
     -1.0
      
   d) 0
      0.0
     -0.0


15) Which abstract class in java is resonsible for binary i/o operations?

   a) Reader
      Writer
      
   b) InputReader
      OutputReader
      
   c) StreamReader
      StreamWriter
      
   d) InputStream
      OutputStream

      
16) The java.io.File class is responsible for what operations?

   a) deleting a file or directory
   b) creating a new file
   c) reading a file
   d) writing a file
   e) getting the file size
   

17) The OutputStreamWriter class is designed for what? (pick one)

   a) writing buffered binary data
   b) reading buffered binary data
   c) writing a character stream as a binary stream
   d) reading a character stream as a binary stream


18) Which of the following a Collection interfaces?

   a) Set
   b) TreeMap
   c) HashMap
   d) List
   e) Vector
   

19) Which Collection(s) are 'implementation' for a group of 
    sorted unique elements?

   a) Map
   b) SortedMap
   c) SortedSet
   d) HashMap
   e) TreeSet
   

20) Which Component(s) generate a ItemEvent?

   a) Container
   b) Window and it's subclasses
   c) List
   d) CheckboxMenuItem
   

21) You are creating a simple AWT application that is going to have a menu and 
    one button, the application is designed to close when the button is clicked
    on. What packages 'must' you import for the program to compile?

   a) java.awt.*;
   b) java.awt.events.*;
   c) java.lang.*;
   d) java.util.*;
   

22) Which ones are not java listener interface? (select all valid answers)

   a) FocusListener
   b) KeyInputListener
   c) WindowListener
   d) EventListener
   e) MouseFocusListener
   

23) How many threads does the following program have after line 1?

public class Test {
   public static void main(String[] args) {
      Worker w1 = new Worker();
      Worker w2 = new Worker();      
      w1.run();
      w2.run();       //line 1
      try {
         Thread.sleep(5000);
      }
      catch(InterruptedException e) {
      }
   }   
}

class Worker implements Runnable {
   public void run() {
      for(int i=0; i<10000; ++i) {
         System.out.println("Running...");
      }
   }
}

   a) two threads
   b) one thread
   c) three threads
   d) program will not compile
   

24) What will happend if the following program is compiled and run?

public class Test {
   public static void main(String[] args) {
      final int n[] = {2,5,3,9};
      Double(n);
      for(int i=0; i<n.length; ++i) {
         System.out.println(n[i]);
      }   
   }   

   static void Double(int a[]) {
      for(int i=0; i<a.length; ++i) {
         a[i] = 2*a[i];
      }   
   }
}

   a) output will be 2,5,3,9 since n is a final variable
   n) will compile but throw an exception when run
   b) will not compile
   d) output will be 4,5,6,9


25) Select all valid java identifiers (used for naming variables).

   a) NULL
   b) _2
   c) String
   d) default
   e) $java
   

27) Will for following code compile? (Yes/No)

interface I {
   void showIt();
}

abstract class A implements I {
   int n;
   
   A(int n) {
      this.n = n;
   }
}

class B extends A {
   B(int n) {
      super(n);
      this.n *= 2;
   }
   
   public void showIt() {
      System.out.println(n);
   }
}


28) The following program will not compile, which lines are in error?

interface I {
   void showIt() {          
      System.out.println(); // line 1
   }                        
}

abstract class A implements I { // line 2   
   int n;
}

class B extends A {
   B(int n) {
      this.n = n;  // line 3
   }
   
   void showIt() {           // line 4
      System.out.println(n);
   }
}

   a) line 1, can't declared method body
   b) line 2, method showIt() not overriden
   c) line 3, class b does not define the variable 'n'
   d) line 4, missing an access modified


29) an anonymous class? (pick all valid answers)

   a) is a class without a body
   b) is a class without a name
   c) can only be declared as an inner-class
   d) is declared within a function call
   e) does not have a constructor
   

30) What will happen if this program is compiled and run?

public class Test {
   public static void main(String[] args) {
      A a = new B(5) {
         public void showIt() {
            System.out.println(n);
         }
      };
      a.showIt();
   }
}


class A {
   int n;
   
   void showIt() {
      System.out.println("Class A"); 
   }
   
   A(int n) {
      this.n = n;
   }
}

class B extends A {
   B(int n) {
      super(n);
      this.n *= 2;
   }  
    
   void showIt() {
      System.out.println("Class B"); 
   }
}

   a) will not compile
   b) compiles but throws and exception when run
   c) displays the string "Class A"
   d) displays the string "Class B"
   e) output the value 10
   f) output the value 5