Java Review Questions, by Rajinder Yadav

These are my review question I made while preparing for my SCJP2 Exam. 

In following with the Linux/OpenSource/OpenDoc philosophy, I am making my java
question available for free to the public under the GNU FDL (GNU Free 
Documentation License).

      Java Review Questions
      Copyright (c)  2002  Rajinder Yadav
      Permission is granted to copy, distribute and/or modify this document
      under the terms of the GNU Free Documentation License, Version 1.1
      or any later version published by the Free Software Foundation;
      with no Invariant Sections, with the no Front-Cover Texts, and with 
      no Back-Cover Texts being LIST. A copy of the license is included in
      the section entitled "GNU Free Documentation License".
      

      web: www.rajindery.com
      email:rajindery@yahoo.com
      
A copy of the GNU FDL can be obtained at, http://www.gnu.org/licenses/fdl.html


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You may send your comments, suggestions and corrections to:

Rajinder Yadav
email: rajindery@yahoo.com

</notice>

+--------------------------------------------------------+
| How to use my notes                                    |
+--------------------------------------------------------+
I would suggest that you print out a copy of my notes and use them along with
other reading material. I have done my best to give each topic it's own section
so you can use my notes as a quick refresher.

Once you are able to read my notes in it's entirety, I would suggest that you
take a look at my java questions, they are designed to test you on what you
already know from my notes and your reading. My review question can be picked
up at:

   http://www.rajindery.com/javacert/jtest.txt

I suggest that you save my review questions for the last week before taking
your exam, you can then use my answer sheet which also contains the questions,
together they will provide you a way to refresh your memory and keep you sharp!

I've taken my free time to make this available for you, now please take some
time to give back.... in the immortal words of Jerry Maguire, 
"Help me help you!"

+--------------------------------------------------------+
| How to help out and give back                          |
+--------------------------------------------------------+
First please read the FDL agreement contained in this document.

If you found these my review questions to be helpful, please share them with 
others so they may also benefit in their preparation for the SCJP2 Exam, better
yet direct them to this site so they can pick up the latest copy!

To give back, I would encourage you strongly to come up with a few 'tough' 
questions of your own, and send them to me for inclusion in this document. 
Please do not send me copies of someone else's original work!

Other ways to help,

* help translate the documents and test questions for another languages
* proof read for typos, errors, clarification
* review information for technical accuracy
* help maintain all information current, advise on deprecated APIs, etc.

btw, when you make your first million, please don't forget about me :^D

+--------------------------------------------------------+
| java basics                                            |
+--------------------------------------------------------+

1) which packages get imported implicitly, select all valid answers

   a) java.lang.Vector
   b) java.util.*;
   c) java.langs.*;
   d) java.lang.Object;
   e) java.lang.Math;


2) which packages get imported implicitly, select all valid answers

   a) java.lang.boolean
   b) java.lang.String;
   c) java.lang.Int;
   d) java.langs.Float;
   e) java.math.BigDecimal;
   f) java.lang.Void;

3) will an empty sourcefile fur.java produce an error when compiled (t/f)

4) what type of value is a char

   a  8-bit signed
   b 16-bit signed
   c 16-nit unsigned
   d 32-bit signed
   e 32-bit unsigned
   

5) select all valid java keywords

   a) throws
   b) catches
   c) throw
   d) then

6) select all valid java keywords

   a) Void
   b) int
   c) sizeof
   d) interface

7) what is the bit depth of an integer value

   a)  8-bits
   b) 16-bits
   c)  7-bits
   d) 32-bits
   
8) select all valid java keywords

   a) if
   b) private
   c) finally
   d) final

9) select all valid java keywords

   a) try
   b) native
   c) break
   d) exit

10) select all valid java identifier

   a) _2big
   b) $name
   c) case
   d) a2b

11) select all valid java keywords

   a) super
   b) New
   c) byte
   d) bool

12) select all valid java keywords

   a) synchronized
   b) true
   c) false
   d) do

13) select all valid java keywords

   a) null
   b) goto
   c) delete
   d) jump

14) select all valid java identifier

   a) null
   b) int32
   c) %item
   d) File_ptr

15) the operator >> works with unsigned values (t/f)

16) which ones are the short-circuit operators

   a) &
   b) ^
   c) ||
   d) ==
   e) &&
   f) +=

17) is this valid (y/n)
 float = 10.0;

18) is this valid (y/n)
 int i = 127;
 byte b = i;
 
19) is this valid (y/n)
 byte b = 128;

20) is this valid (y/n)
 int i = 10;
 i += 5;

21) is this valid (y/n)
  int i = 1;
  char b = i?'a':'b';
  
22) list all valid assignments

   a) char = "b";
   b) char = \u0000;
   c) char = 018;
   d) char = 0x10;
   e) char = 'f';
   f) char = 512;

23) is this valid (y/n)
 int i = 10;
 char c = i;
 
24) is this valid (y/n)
 char c = 0xff;
 int i = c;
 
25) what will be the output from the following program

public class Test {
   boolean b;
   int i=0;
   public static void main(String[] args) {
      for(i=0; i<10; ++i) {
         System.out.println(b);
      }
   }
}

   a) will not compile since variable b is not initialized before use
   b) prints 'true' ten times
   c) prints 'false' tem times
   d) compiler error stating non-static access from a static context

26) what results from the following statements

   boolean b = false;
   (8 == 3) || b = true;

   a) won't compile
   b) b will be false
   c) b will be true

27) list all valid java array declarations

   a) char []a = new int[5];
   b) int a[5] = {1,2,3,4,5};
   c) int n[] = new[] {5,5,5};
   d) int* p = int[10];
   e) long []a[];
   f) long a[3][];

28) what will happen if the following code is compiled and run

public class Test {
   public static void main(String[] args) {
      byte b = -1;
      
      switch(b) {
         default:
            System.out.println("Z");
         case 0:
            System.out.println("A");
            break;
         case 1:
            System.out.println("B");
            break;
      }
   }      
}   

   a) will output Z
   b) will not compile since default must be the last test case 
   c) will output Z and A
   d) will not compile since argument to switch must be type int

29) what results from the following statements

   boolean b = false;
   (1 == 1) && b = true;

   a) won't compile
   b) b will be false
   c) b will be true

30) what will happen if the following program is compiled and run

public class Test {
   public static void main(String[] args) {
   float f[] = new float[10];
      for(int n=0; n<f.length; ++n) {
         System.out.println(f[n]);
      }
   }
}

   a) will output 0 ten times
   b) will not compile since i.length is not a valid statement
   c) compiler error since array i has not been initialized
   d) will output 0.0 tem times

31) will this compile (t/f)
   
   int i=10/0;

32) what will be the result of the following statements

float f=10.0f/0;
System.out.println(f);

   a) will not compiler, we have a divide by zero
   b) will compile, run and display a value of 'Infinity'
   c) will compile but throws an exception when run
   d) will not compile, can't divide a floating proint value 
      with a integer value
   e) will compile, run and display 'NaN'

33) selected all valid integer literals

   a) 10
   b) 1e-10
   c) 0.0F
   d) 012
   e) 0Xa
   f) 058

34) what is the result of the following statements

   int n = 2;
   n = n>>33;

   a) n will have a value of 1
   b) n will be some negative number
   c) a compiler error, cannot left shift more then the bit depth of a value
   d) n will be zero

35) In method init() how many objects are created

   class A {}
   
   void init() {   
      A a1;
      A a2[] = new[5];
   }
   
   a) 0 objects
   b) 1 object
   c) 2 objects
   d) 5 objects
   e) 6 objects

36) what will be the result if the following program is compiled and run?

public class Test {
   public static void main(String[] args) {
      int n = methodX(8);
      System.out.println(n);
   }
   
   static int methodX(int j) {
      int i;
      switch(j) {
         case 0:
            i=-12;
            break;
         case 8:
            i=++j;
            break;               
      }
      return i--;
   }
}

a) the value 8 will be output
b) the value 9 will be output
c) the value 7 will be output
d) will not compile

37) what will happend if this program is compiled and run

public class Test {
   public static void main(String[] args) {
      System.out.println(sum(5));
   }
   
   static int sum(int i) {
      if(i == 0) {
         return 0;
      }
      return i+sum(i-1);
   }
}

   a) the output will be 9
   b) no output the program will never end
   c) will not compile since a function cannot make a call to itself
   d) the output will be 45
   
38) assumming Quicksort is a static final class that implements the quicksort 
    algorithm, will this program compile. (y/n)

import com.yadav.utils.Quicksort;
import com.acme.Quicksort;

public class Test {
   public static void main(String[] args) {
      int n[] = {12,6,29,-3,3,66,21};

      Quickstort.int(n);
   }
}

39) what will happen if this program is compiled and run

public class Test {
   public static void main(String[] args) {
      int i[][] = new int[2][];
      i[0] = new int[3];
      i[1] = new int[5];
      System.out.println(i.length);
   }
}

   a) will result in a compile error
   b) will output the value 10
   c) will output the value 8
   d) will output the value 2

40) given the statement 'final int n=10;', we can say that 'n' is an 
    interger literal (t/f)

41) what will happen if the following program is compiled and run

public class Test {
   public static void main(String[] args) {
      int a[] = new int[5];
      System.out.println(a instanceof Object);
   }
}

   a) an runtime exception will be thrown
   b) the output will be 'true'
   c) the output will be 'false'
   d) will not compile
   
42) will the variable initialization process complete correctly in this code? 
    (select all valid answers)

public class Test {
   static char c1;
   char cc =c1;         // line 1
   static char c2 = c3; // line 2
   int i = c1;          // line 3
   static char c3 = 'r';
   
   public static void main(String[] args) {
   }
   
   static {     // line 4
      c1 = c3;  
   }
}

   a) breaks at line 1, cannot initialize a instance field from a static field
   b) breaks at line 2, cannot forward reference with static field
   c) compiles without error
   d) breaks at line 3, cannot initialize an int field with a char field
   e) breaks at line 4, cannot initialize like this

43) what will happen if this program is compiled and run
   
public class Test {
   static int b1 = initMe();
   static int b2 = 10;
   
   public static void main(String[] args) {
      int b3 = b1 + b2;
      
      System.out.println(b3);
   }
   
   static int initMe() {
      return b2;      
   }   
}

   a) will output the value '20'
   b) will not compile
   c) will output the value '10'

+--------------------------------------------------------+
| java classes                                           |
+--------------------------------------------------------+

1) what is a top-level class, select the most appropriate answer

   a) the first class declared in the sourcefile
   b) a static inner class
   c) a public inner class
   d) a public non-inner class

2) can a source file contain many public classes (t/f)

   a) true
   b) flase

3) is the Object class the super-class for all java classes (t/f)

4) if a class is declared with no access modifier, is it visible to 
   other classes in the same package (y/n)

5) are default class fields visible to classes outside package (y/n)

6) inorder to create a class that can be subclassed, it must: 
   (select all valid answers)

   a) be declared public
   b) cannot be an abstract class
   c) it must not have a private constructor
   d) cannot be an inner-class
   e) should not be a static class

7) does a static inner class have access to public fields of it's 
   outer class (y/n)

8) can an inner class be declared abstract (y/n)

9) can an interface have a non-abstract method? (y/n)

9) can an interface have a field member? (y/n)


10) if a class implements an interface, which of the following are true 

   a) the class must be non-static
   b) the class cannot be abstract
   c) the class cannot be declared as final
   d) the class needs to be in the same package as the interface
   e) an abstract class dose not need to implement the interface methods

11) can an interface implement multiple interfaces using the 
    extends keyword (y/n)

12) list two things wrong with the following code

interface I {}
interface J extends I{}
interface K {}

public class A {}
public class B {}
class C extends A, B implements I, K {}

   a) an interface must be declared 'public abstract'
   b) cannot have multiple top-level public classes
   c) an interface can't extend another interface
   d) a class cannot implment more than one interface
   e) a class cannot subclass more than one class

13) what is the result if the following code is compiled and run

public class Test {
   public static void main(String[] args) {
      B b = new B(0);
   }
}

class A {
   int a;
   A(int a) {
      this.a = a;  // line 1
   }
}

class B extends A {
   B(int a) {
      System.out.println("I'm alive!");
   }
}

   a) will compile and display the string "I'm alive!"
   b) will not compile since statement at line 1 is illegal
   c) will not compile since a default no-argument ctor is missing in class B
   d) will compile but throw an exception when run because of a missing 
      no-arg ctor in class A
   e) will not compile since a default no-argument ctor is missing in 
      the base class A

14) if the following code is compiled and run, what will be the result

public class Test {
   public static void main(String[] args) {
      A.B b = new A.B();   \\ line 1
   }
}

class A {
   static class B { \\ line 2
      B() {         \\ line 3
         System.out.println("I'm Alive!");
      }
   }
}


   a) will not compile since line 1 is not valid
   b) will run and display the string "I'm Alive!"
   c) will break at line 3, static classes cannot declare a ctor
   d) will break at line 3, static classes cannot declare a ctor

15) how can we change the code so it will compile and run

public class Test {
   public static void main(String[] args) {
      B b = new B();
   }
}

class A {
   
   //A() {}          // line 1
   A(int a) {}
}

class B extends A {
   // B()            // line 2
   B(int a) {
      //super.A(a);  // line 3
      //super(a);    // line 4
   }
}

   a) uncomment line 1
   b) uncomment line 2
   c) uncomment line 3
   d) uncomment lines 1 and 2
   e) uncomment line 4

16) can a ctor have a return statement (t/f)

class A {   
   A() {
      return;
   }
}

17) can a ctor have a return value (y/n)

18) can a ctor be declared as private (y/n)

19) can the following class be compiled and created using 'A = new A();' (y/n)

class A {
   int b;
   
   A() {
      this(10);
   }
   
   A(int b) {
    this.b = b;
 }
 
20) subclasses are created before their superclasses (t/f)

21) a ctor with not access modifier will have which access visibility

   a) public
   b) default
   c) same visibility as the class
   d) private

22) will the following code compile and run (y/n)

public class Test {
   static int i;
   public static void main(String[] args) {
      System.out.println(i);
   }
}

23) what will happen if the following code is compiled and run

public class Test {   
   {  
      System.out.println("A");
   }
     
   Test() {
      System.out.println("C");
   } 
           
   public static void main(String[] args) {
      System.out.println("D");
      Test t = new Test();
   }
   static {
      System.out.println("B");
   }
}

   a) will output the lines A,B,C,D
   b) will output the lines A,C,D,B
   c) will output the lines B,D,C,A
   d) will output the lines D,C,A,B
   e) will output the lines B,D,A,C
   f) will will a compiler error

24) to make the following code compile and run, what needs to be done

public class Test {   
   public static void main(String[] args) {     
      B b = new B(0);
   }
}
class A {
   A(int a) { }
}

class B extends A {
   B() {
      super(1);
   }
   
   B(int i) { 
      int i=0; // line 1
      this();  // line 2
   }
}

   a) delete line 1  <---(ans)
   b) delete line 2
   c) delete lines 1 and 2

25) what needs to be added at 'XX' to make class A compile without error

interface I {
   void init();
}

'XX' class A implements I{
}

   a) static
   b) public
   c) final
   d) abstract


26) if the following code is compiled what will happen

abstract class A {
   void init() {
      System.out.println("XXX");
   }
}

class B extends A {
}

   a) will compile without error
   b) will not compile since class B does not declare method 'void init()'
   c) will not compile since class B must be declared as abstract
   d) will not compile, cannot extend a abstract class
   e) will not compile, abstract class A cannot declare a non-abstrace method


27) what will happen if the following code is compiled and run

public class Test implements I {
   public static void main(String[] args) {
      System.out.println(s);
   }   
}

interface I {
   String s = "Welcome!";
}

   a) the string "Welcome!" will be displayed
   b) will not compile 
   c) will compile but throw an exception when run

28) what will happen if the following code is compiled and run

public class Test  implements I {
   static String s = "Do not Enter!!!";
   public static void main(String[] args) {
      System.out.println(s);
   }   
}

interface I {
   String s = "Welcome!";
}

   a) the string "Welcome!" will be displayed
   b) will not compile 
   c) will compile but throw an exception when run
   d) the string "Do not Enter!!!" will be displayed

29) what will happen if the following code is compiled and run

public class Test  {
   String s = "Hello!";
   public static void main(String[] args) {
      System.out.println(s);
   }   
}  

   a) will display the string "Hello!"
   b) will compile but throw an exception with it's runs
   c) will not compile

30) fields declared with no modifiers inside an interface are 
    considered to be 'public static final' (t/f)

31) what will happen if the following code is compiled and run

public class Test  implements I {
   static String s = "Do not Enter!!!";
   public static void main(String[] args) {
      String s = "Please Come In!";
      System.out.println(Test.s);
   }   
}

interface I {
   String s = "Welcome!";
}

   a) will display the string "Welcome!"
   b) will compile but throw an exception with it's runs
   c) will not compile
   d) will display the string "Do not Enter!!!
   e) will display the string "Please Come In!"

32) what will happen if the following code is compiled and run

public class Test  implements I {
   static String s = "Do not Enter!!!";
   public static void main(String[] args) {
      String s = "Please Come In!";
      System.out.println(I.s);
   }   
}

interface I {
   String s = "Welcome!";
}

   a) will display the string "Welcome!"
   b) will compile but throw an exception with it's runs
   c) will display the string "Please Come In!"
   d) will display the string "Do not Enter!!!
   e) will not compile

33) what will happen if the following code is compiled

public class Test  implements I {
   public static void main(String[] args) {
      B b = new B();
   }   
}

class A {
   private A() {
   }
}

class B extends A {
}

   a) since ctor's are not inherited, will compile without any error
   b) will not compile, since ctor in class A is declared private
   c) will not compile, since a top-level class cannot declare a private ctor
   d) will not compile, since it is not primitted to declare a ctor as private

34) what will happen is the following code is compiled and run

public class Test {
   public static void main(String[] args) {
      Shape s = new Circle();    // line 1
      Box b = new Box();
      
      s.draw();
      b.draw();
   }   
}

abstract class Shape {
   void draw() {
      System.out.println("Shape");
   }
}

class Circle extends Shape {      
   void draw() {
      System.out.println("Circle");
   }
}

class Box extends Shape {
   protected void draw() {    // line 2
      System.out.println("Box");
   }
}

   a) will show the strings "Shape" and "Box"
   b) will show the strings "Shape" and "Shape"
   c) will not compile because of line 1
   d) will show the strings "Circle" and "Shape"
   e) will compile but throw an exception when run
   f) will show the strings "Circle" and "Box"
   g) will not compile because of line 2, because of access modifier 'protected'

35) if class A extends class B and implements an interface I, which of 
    the following statement is true

   a) class A is a subclass ob class Object
   b) an object of class A is an instance of I
   c) an object of class A is an instance of B
   d) an object of class B is an instance of A
   e) B is a superclass of A

36) a method declared in a subclass having the same name, return type and 
    argument list is an example of

   a) overloading a method
   b) overridding a method
   c) is not allowed 

37) a conversion from an reference type 'X' to a reference type Object is 
    possible without requiring a cast (t/f)

+--------------------------------------------------------+
| exception handling                                     |
+--------------------------------------------------------+

1) all uncaught exceptions cause the running process to be killed (t/f)


2) what lines will be output

public class Test {
   public static void main(String[] args) {
      try {
         System.out.println("A");
         int i=5/0;
         System.out.println("B");
      }
      catch(ArithmeticException e) {
         System.out.println("C");
      }
      catch(Exception e) {
         System.out.println("D");
      }
      finally {
         System.out.println("E");
      }
      System.out.println("F");
   }     
}

   a) lines A,E,F
   b) lines A,B,E,F
   c) lines A,C,E,F
   d) lines A,C,B,E,F
   e) Lines A,C
   f) lines A,E

3) what is the most likely output

public class Test {
   public static void main(String[] args) {
      try {
         System.out.println("A");
         int i=5/0;
         System.out.println("B");
      }
      finally {
         System.out.println("E");
      }
      System.out.println("F");
   }  
}

a)
   A
   Exception in thread "main" java.lang.ArithmeticException: / by zero
   
b)

   A
   E
   Exception in thread "main" java.lang.ArithmeticException: / by zero
c)
   A
   E
   F
   Exception in thread "main" java.lang.ArithmeticException: / by zero

4) given the following Excepetion class heirarchy, is the following try/catch 
   block valid (y/n)

      Exception
          |
          +-RuntimeException
             |
             +-ArithmeticException

   try {
   }
   catch(Exception e) {
   }
   catch (ArithmeticException e) {
   }

5) if an exception is caught inside a function call

   a) exception continues after the line the exception took place
   b) exception continues after the exception handler block
   c) the method returns after exception handler completes

6) given the following Excepetion class heirarchy, will class B compile (t/f)

      Exception
          |
          +-RuntimeException
             |
             +-ArithmeticException

class A {
   void sum(int a, int b) throws Exception {}
}

class B extends A {
   void sum(int a, int b) throws ArithmeticException {}
}

7) the RuntimeException class and all it's sub-classes are 'checked' 
   exception (t/f)

8) a Error exception class and all it's sub-classes are 'unchecked' 
   exception (t/f)

9) the Exception class is the super-class for all exception classes (t/f)

10) what will be the output

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

   a) strings A B X
   b) strings B X
   c) string B X A

11) given the following class relationships, select all valid answers

interface I {}
class A {}
class B extends A{}
class C extends A implements I {}

   a) class B extends A is an example of a 'is-a' relationship
   b) class C implements I is an example of a 'has-a' relationship
   c) class C is said to contain class A
   d) class A is the superclass of class C
   e) class B derives from class A
   f) class B is a subclass of class C


+--------------------------------------------------------+
| string immutability & garbage collection               |
+--------------------------------------------------------+

1) what will be the output of the following program

public class Test {
   public static void main(String[] args) {
      String s = "good";
      s.concat("bye");
      System.out.println(s);
   }
}

   a) string "good"
   b) string "goodbye"


2) what will be the output of the following program

public class Test {
   public static void main(String[] args) {
      String s1 = "good";
      String s2;
      
      s2 = setString(s1);
      System.out.println(s1);
      System.out.println(s2);      
   }
   
   static String setString(String s) {
      s = "bye";
      return s;
   }
}

   a) strings "good" and "good"
   b) strings "bye" and "bye"
   c) strings "good" and bye"

3) what will be the output of the following program

public class Test {
   public static void main(String[] args) {
      String s1 = "good";
      String s2;
      
      s2 = setString(s1);
      System.out.println(s1);
      System.out.println(s2);      
   }
   
   static String setString(String s) {
      s.concat("bye");
      return s;
   }
}

   a) strings "goodbye" and "goodbye"
   b) strings "good" and "goodbye"
   c) strings "good" and "good"


4) what will be the output of the following program

public class Test {
   public static void main(String[] args) {
      String s1 = "good";
      String s2;
      
      s2 = setString(s1);
      System.out.println(s1);
      System.out.println(s2);      
   }
   
   static String setString(String s) {
      s = s.concat("bye");
      return s;
   }
}

   a) strings "goodbye" and "goodbye"
   b) strings "good" and "goodbye"
   c) strings "good" and "good"

5) when is the earliest that string "good" become eligible for GC

public class Test {
   public static void main(String[] args) {
      String s1 = new String("good");
      String s2;
      
      s2 = dup(s1);
      s2 = null;     // line 3
      s1 = dup(s2);  // line 4
   }          
   
   static String dup(String s) {
      String ss = s;
      s = null;      // line 1
      return ss;
   } // line 2
}

   a) after line 1
   b) after line 2
   c) after line 3
   d) after line 4
   e) never

6) what will the output be

public class Test {
   public static void main(String[] args) {
      String s1 = new String("good");
      String s2 = s1.toString();
      System.out.println("s1 == s2 " + (s1 == s2));
   }
}

   a) the string "s1 == s2 false"
   b) the string "s1 == s2 true"

7) what will be the output of the following program

public class Test {
   public static void main(String[] args) {
      String s1 = "Good" + "bye";
      String s2 = "Good" + "bye";
      String s3 = "Goodbye";
      
      System.out.println("s1 == s2 : " + (s1 == s2));
      System.out.println("s1 == s3 : " + (s1 == s3));      
    }
}

   a) s1 == s2 : false
      s1 == s3 : false

   b) s1 == s2 : true
      s1 == s3 : false

   c) s1 == s2 : true
      s1 == s3 : true

   d) s1 == s2 : false
      s1 == s3 : true


8) when will string s1 become eligible for garbage collection?

public class Test {
   static String s;
   public static void main(String[] args) {
      String s1 = new String("Mewow!");
      s = s1;        // line 1
      s1 = null;     // line 2
      killString(s);
   }
   
   static void killString(String s) {
      s = null;      // line 3
   }
}

   a) after line 1
   b) after line 2
   c) after line 3
   d) never

9) what will be the output

public class Test {
   static String s;
   public static void main(String[] args) {
      String s1 = new String("First");
      String s2 = new String("Second");
      swapString(s1, s2);
      System.out.println(s1+s2);
   }
   
   static void swapString(String s1, String s2) {
      String temp = s1;
      s1 = s2;
      s2 = temp;
   }
}

   a) the string "FirstSecond"
   b) the string "SecondFirst"



+--------------------------------------------------------+
| package java.lang                                      |
+--------------------------------------------------------+

1) what will happen if this program is compiled and run

public class Test {
   public static void main(String[] args) {
      long l = Long.MAX_VALUE;
      ++l;
      long r = Math.abs(l);
      System.out.println(r);
   }
}

   a) the output will be '0'
   b) an overflow exception will be thrown
   c) the output will be '-9223372036854775808'


+--------------------------------------------------------+
| threads                                                |
+--------------------------------------------------------+

if this program is run, when will the process terminate

public class Test {
   public static void main(String[] args) {
      A a = new A();
      B b = new B();
      a.start();
      b.start();
   } // line 1
}    // line 2

class A extends Thread {
   A() {
      setDaemon(true);
   }
   
   public void run() {
      // loop forever
      while(true) { 
         System.out.println("Still running...");
      }
   } 
}

class B extends Thread {
   public void run() { 
      // loop for a little while
      for(int i=0; i<1000; ++i) {
         System.out.println("String going...");
      }
   } // line 4
}

   a) after line 1
   b) after line 2
   c) after line 4
   d) only after the main thread and thread 'b' both exit
   e) never, since thread 'a' runs in a infinte loop and never dies


+--------------------------------------------------------+
| java AWT components                                    |
+--------------------------------------------------------+





question to add

* given a file named 'Test.java', determine if the following will 
  compile and run (y/n)

class Test {
   public static void main(String[] args) {
      TestClass tc = new TestClass("Hello!");
      tc.out();
   }   
}

public class TestClass {
   String name;
   
   TestClass(String s) {
      name = s;
   }
   
   void out() {
      System.out.println(name);
   }
}


* a compiler error will result if we try to explicitly import 
  the java.lang.* package since it gets imported implicitly by javac (t/f)


* will the following code compile and run

import java.lang.*;
import java.lang.*;

class Test {
   public static void main(String[] args) {
      TestClass tc = new TestClass("Hello!");
      tc.out();
   }   
}

class TestClass {
   String name;
   
   TestClass(String s) {
      name = s;
   }
   
   protected void out() {
      System.out.println(name);
   }
}

   a) it will compile and out put the string "Hello!" when run
   b) it will compile but throw a runtime exception since 'class Test' 
      has not been declared public
   c) will not compile, since there is a duplicate import statement
   d) will compile but thrown a runtime exception since object 'tc' 
      tries to access a method that's not public
   

* what will happen when the following program is compiled and run

public class Test  {
   public static void main(String[] args) {
      new A().start();
      new B().start();
   }   
}  

class A extends Thread {
   public void run() {
      int i=10/0;
   }
}

class B extends Thread {
   public void run() {
      while(true) { 
         System.out.println("Running...");
      }
   }
}

a) will print the string "Running..." forever
b) the process will terminate when a divide by zero exception is 
   raised by one of the threads
c) will not compile

* what will happen when the following program is compiled and run

public class Test  {
   public static void main(String[] args) {
      String s = "Hello!";
      s = "Goodbye";
      System.out.println(s);      
   }   
}  

a will not compile, strings are immutable so they cannot 
  be assigned a 2nd string
b will compile and output the string "Hello!" when run
c will compile and output the string "Goodbye" when run