Ôn thi tốt nghiệp: java + uml ( in oop (using java) subject ) Question 1

Examine the following switch block:

char mychar = c;

switch (mychar) {

default:

case 'a': System.out.println("a"); break;

case b: System.out.println("b"); break;

}

Which of the following questions are definitely true?

1. 
   When this code runs, the letter "a" is written to the standard output.
   
2. 
   When this code runs, nothing is writ en to the standard output.
   
3. 
   This switch block is illegal, because the default statement must come last.
   
4. 
   This switch block is illegal, because only integers can be used in the switch statement.
   
5. 
   This switch block is fine
   

Examine the statements below. Which of the statements correctly describes the hierarchy of MenuItem and CheckboxMenuItem classes?

1. The CheckboxMenuItem class extends the MenuItem class to support a menu item that may be checked or unchecked.

2. The MenuItem class extends the CheckboxMenuItem class to support a menu item that may be checked or unchecked.

1. 
   2
   
2. 
   Neither
   
3. 
   1
   
4. 
   1 and 2
   

For THIS question, consider this code fragment:

int x = 10;

try {

x = foo();

x++;

} catch (Exception e) {}

For the above, assume that 1) it compiles and runs, and 2) that method foo() throws an Exception during execution.

What is the output?

1. 
   x = 5
   
2. 
   x = 6
   
3. 
   Whatever the return value of foo() is.
   
4. 
   x = 10
   

garbage collection?

2. 1. import java.util.*;

3. 2. public class Question {

4. 3. public static void main(String[] args) {

5. 4. Vector v1 = new Vector(); a

6. 5. Vector v2 = new Vector();

7. 6. v1.add("This");

8. 7. v1.add(v2);

9. 8. String s = (String) v1.elementAt(0);

10. 9. v1 = v2;

11. 10. v2 = v1;

12. 11. v1.add(s);

13. 12. }

13.}YÙ

1. 
   Line 9
   
2. 
   Line 8
   
3. 
   Line 6
   
4. 
   Line 5
   

Given:

1. class Test{

2. Bar doBar(){

3. Bar b=new Bar();

4. return b;

5. }

7. Test t=new test();

8. Bar newBar=t.doBar();

9. System.out.println("newBar");

10. newBar=new Bar();

11. System.out.println("finishing");

12. }

13. }

1. 
   After line 10.
   
2. 
   After line 8.
   
3. 
   After line 11, when main() completes.
   
4. 
   After line4, when doBar() completes.
   

Given:

2 static boolean b;

3 public static void main(String [] args) {

4 int x=0;

5 if (b ) {

6 x=1;

8 else if (b = false) {

9 x=2;

10 }

12 x=3;

14 else {

15. 
    x=4;
    

17 System.out.println("x = " + x);

18 }

19 }

1. 
   x = 4
   
2. 
   Compilation fails
   
3. 
   x = 2
   
4. 
   x = 1
   
5. 
   x = 3
   
6. 
   x = 0
   

Given:

2. private Demo d;

3. void start(){

4. d=new Demo();

5. this.takeDemo(d);

6. }

8. void takeDemo(Demo demo){

9. demo=null;

10. demo=new Demo();

11. }

12. }

1. 
   When the takeDemo() method completes.
   
2. 
   After line 9.
   
3. 
   When the instance running this code is made eligible for garbage collection.
   
4. 
   After the start() method completes.
   
5. 
   After line 5.
   

Given:

2.

4. Birthdays() {

5. super("Birthday Reminder");

6. String lblsP1[] = {"Name:", "Birthday:", "Address:"};

7. String butnsP2[] = {"Add", "Save", "Exit"};

8. Panel panelTop = new Panel();

9. Panel panelBot = new Panel();

10. panelTop.setLayout(new GridLayout(3,2,3,3));

11. for(int x = 0; x < lblsP1.length; x++) {

12. panelTop.add(new Label(lblsP1[x]));

13. panelTop.add(new TextField());

14. }

16. panelBot.add(new Button(butnsP2[y]));

17. }

18. add(panelTop, BorderLayout.NORTH);

20. }

Which main method should you add to the Birthdays class to allow the program to compile and run with all defined fields properly displayed?

a) public static void main(String args[]) { Frame f = new Frame();

f.setVisible(true);}

b) public static void main(String args[]) { Frame f = Birthdays.new

Frame(); f.pack(); f.visible = true; }

c) public static void main(String args[]) { Birthdays b = new

Birthdays(); b.pack(); b.setVisible(true); }

d) public static void main(String args[]) { Frame.visible = true; }

Question 89–c

Given:

2. import java.util.Vector;

3. private class My Vector extends Vector {

4. int i = 1;

. 5. public My Vector() {

6. i = 2; } }

7. public class MyNewVector extends My Vector {

8. public MyNewVector () {14. i = 4; }

9. public static void main (String args []) {

10. My Vector v = new MyNewVector (); } }

What is the result?

1. 
   Compilation fails because of an error at line 14.
   
2. 
   Compilation fails because of an error at line 17.
   
3. 
   Compilation fails because of an error at line 5.
   
4. 
   Compilation fails because of an error at line 6.
   
5. 
   Compilation succeeds.
   

Given:

2. public static void main(String[]args){

3. try{

4. badMethod();

6. }

8. System.out.print("B");

9. }

10. finally{

12. }

14. }

16. throw new RuntimeException();

17. }

18. }

1. 
   BCD
   
2. 
   Compilation fails.
   
3. 
   BC
   
4. 
   ABC
   
5. 
   AB
   

Given:

2. int frood=42;

3. }

4. class Testlmpl implements Test{

6. System.out.printIn(++frood);

7. }

8. }

1. 
   43
   
2. 
   42
   
3. 
   Compilation fails.
   
4. 
   0
   
5. 
   1
   
6. 
   An exception is thrown at runtime.
   

Given:

11. Object o=new Float(3.14F);

12. Object[]oa=new Object[1];

13. ao[0]=o;

14. o=null;

15. oa[0]=null;

16. return o;

17. }

1. 
   Just after line 14.
   
2. 
   Just after line 13.
   
3. 
   Just after line 15.
   
4. 
   Just after line 16(that is, as the method returns).
   

Given:

12. switch(f){

13. case 12:System.out.println("Twelve");

14. case 0:System.out.println("Zero");

15. default: System.out.println("Default");

16. }

1. 
   Zero
   
2. 
   Twelve
   

Default

3. 
   Twelve
   
4. 
   Compilation fails
   
5. 
   Default
   

Given:

12. switch(i){

13. case 0:break;

14. case 1:System.out.print("one");

15. case 2:System.out.print("two");

16. case 3:System.out.print("three");

17. }

18. }

What is the result?

1. 
   Done
   
2. 
   One two three two three done
   
3. 
   Compilation fails.
   
4. 
   One two done
   

Given:

12. public void foo(){

13. assert false;

14. assert false;

15. }

16. public void bar(){

18. assert false;

19. }

20. assert false;

22. }

1. 
   Line 20
   
2. 
   Line 14
   
3. 
   Line 18
   
4. 
   Line 13
   

Given:

12. if(a){

13. System.out.println("A");

14. }else if(a&b){

15. System.out.println("A&B");

16. }else{

17. if( !b ){

18. System.out.println("notB");

19. }else{

20. System.out.println("ELSE");

21. }

22. }

What is correct?

1. 
   If a is true and b is true then the output is "A&B".
   
2. 
   If a is true and be is false then the output is "notB".
   
3. 
   If a is false and b is false then the output is "ELSE".
   
4. 
   If a is false and be is true then the output is "ELSE".
   

Given:

12. int x=0;

13. int y=5/x;

14. }catch(Exception c){

15. System.out.println("Exception");

16. }catch(ArithmeticException ac){

17. System.out.println("Arithmetic Exception");

18. }

What is the result?

1. 
   finished
   
2. 
   Arithmetic Exception
   
3. 
   Exception
   
4. 
   Compilation fails.
   

Given:

21. assert validEmployee(c);

22. float sal=lookupSalary(c);

23. assert (sal>0);

24. return sal;

25. }

27. assert validEmployee(c);

28. int age=lookupAge(c);

29. assert (age>0);

30. return age;

31. }

1. 
   Line 29
   
2. 
   Line 27
   
3. 
   Line 21
   
4. 
   Line 23
   

Given a string constructed by calling s = new String("xyzzy"), which of the calls listed below modify the string?

1. 
   s.trim();
   
2. 
   s.concat(s);
   
3. 
   s.replace(`z', `a');
   
4. 
   s.substring(3);
   
5. 
   None of the others
   

Given the declaration Circle x = new Circle(), which of the following statement is most accurate.

1. 
   x contains an int value.
   
2. 
   x contains a reference to a Circle object.
   
3. 
   You can assign an int value to x.
   
4. 
   x contains an object of the Circle type.
   

Given the following,

1.class Foo {

2. class Bar{ }

3.}

4.class Test {

6. Foo f = new Foo();

7. // Insert code here

8. }

which statement, inserted at line 5, creates an instance of Bar?

1. 
   Foo.Bar b = new f.Bar();
   
2. 
   Foo.Bar b = new Foo.Bar();
   
3. 
   Bar b = f.new Bar();
   
4. 
   Foo.Bar b = f.new Bar();
   
5. 
   Bar b = new f.Bar();
   

Given the following,

1. class MyThread extends Thread {

2.

3. public static void main(String [] args) {

5. t.run();

6. }

7.

8. public void run() {

10. System.out.print(i + "..");

11. }

12. }

what is the result?

1. 
   1..2..
   
2. 
   This code will not compile due to line 5.
   
3. 
   An exception is thrown at runtime.
   
4. 
   This code will not compile due to line 4.
   
5. 
   1..2..3..
   

Given the following,

1. class MyThread extends Thread {

2.

3. public static void main(String [] args) {

5. Thread x = new Thread(t);

6. x.start();

7. }

9. public void run() {

10. for(int i=0;i<3;++i) {

11. System.out.print(i + "..");

12. }

13. }

what is the result of this code?

1. 
   1..2..3..
   
2. 
   0..1..2..
   
3. 
   0..1..2..3..
   
4. 
   Compilation fails.
   
5. 
   An exception occurs at runtime.
   

Given the following,

1. class Test {

2.

3. public static void main(String [] args) {

5. }

7. public static void printAll(String[] lines) {

8. for(int i=0;i

9. System.out.println(lines[i]);

10. Thread.currentThread().sleep(1000);

11. }

13. }

1. 
   Each String in the array lines will output, with no pause in between because this method is not executed in a Thread.
   
2. 
   Each String in the array lines will output, with a 1-second pause.
   
3. 
   This code will not compile.
   
4. 
   Each String in the array lines will output, and there is no guarantee there will be a pause because currentThread() may not retrieve this thread.
   

Given the following,

1. class X2 {

2. public X2 x;

3. public static void main(String [] args) {

4. X2 x2 = new X2();

5. X2 x3 = new X2();

6. x2.x = x3;

7. x3.x = x2;

8. x2 = new X2();

9. x3 = x2;

10. doComplexStuff();

11. }

12. }

1. 
   3
   
2. 
   1
   
3. 
   4
   
4. 
   2
   
5. 
   0
   
6. 
   5
   

Given the following,

1. public class HorseTest {

2. public static void main (String [] args) {

3. class Horse {

4. public String name;

5. public Horse(String s) {

6. name = s;

7. }

8. }

10. Horse h = (Horse) obj;

11. System.out.println(h.name);

12. }

what is the result?

1. 
   An exception occurs at runtime at line 10.
   
2. 
   Compilation fails because of an error on line 11.
   
3. 
   Compilation fails because of an error on line 9.
   
4. 
   Compilation fails because of an error on line 3.
   
5. 
   Zippo
   
6. 
   Compilation fails because of an error on line 10.
   

Given the following,

1. public class HorseTest {

2. public static void main (String [] args) {

3. class Horse {

4. public String name;

5. public Horse(String s) {

6. name = s;

7. }

8. }

10. System.out.println(obj.name);

11. }

12. }

1. 
   An exception occurs at runtime at line 10.
   
2. 
   Compilation fails because of an error on line 10.
   
3. 
   Compilation fails because of an error on line 9.
   
4. 
   Compilation fails because of an error on line 3.
   
5. 
   Zippo.
   

Given the following,

1. public class MyRunnable implements Runnable {

2. public void run() {

3. // some code here

4. }

which of these will create and start this thread?

1. 
   new Thread(MyRunnable).run();
   
2. 
   new Thread(new MyRunnable()).start();
   
3. 
   new MyRunnable().start();
   
4. 
   new Runnable(MyRunnable).start();
   

Given the following,

1. public class Test {

2. public static void main (String [] args) {

3. final Foo f = new Foo();

4. Thread t = new Thread(new Runnable() {

5. public void run() {

6. f.doStuff();

7. }

8. });

10. public void run() {

11. f.doStuff();

12. }

14. t.start();

15. g.start();

16. }

1. class Foo {

2. int x = 5;

3. public void doStuff() {

4. if (x < 10) {

5. // nothing to do

6. try {

7. wait();

8. } catch(InterruptedException ex) { }

9. } else {

10. System.out.println("x is " + x++);

11. if (x >= 10) {

12. notify();

13. }

15. }

what is the result?

1. 
   The code will not compile because of an error on line 7 of class Foo.
   
2. 
   An exception occurs at runtime.
   
3. 
   The code will not compile because of an error on line 12 of class Foo.
   
4. 
   x is 5
   

5. 
   The code will not compile because of an error on line 4 of class Test.
   
6. 
   The code will not compile because of some other error in class Test.
   

Given the following,

1.public class TestObj {

2. public static void main (String [] args) {

3. Object o = new Object() {

4. public boolean equals(Object obj) {

5. return true;

6. }

8. System.out.println(o.equals("Fred"));

9. }

10.}

An exception occurs at runtime.

1. 
   true
   
2. 
   Compilation fails because of an error on line 3.
   
3. 
   Compilation fails because of an error on line 8.
   
4. 
   Compilation fails because of an error on a line other than 3, 4, or 8.
   
5. 
   Compilation fails because of an error on line 4.
   

Given the following,

1. public class X {

2. public static void main(String [] args) {

3. X x = new X();

4. X x2 = m1(x);

5. X x4 = new X();

6. x2 = x4;

7. doComplexStuff();

8. }

10. mx = new X();

11. return mx;

12. }

After line 6 runs. how many objects are eligible for garbage collection?

1. 
   5
   
2. 
   1
   
3. 
   3
   
4. 
   4
   
5. 
   0
   
6. 
   2
   

Given the following,

1. public class WaitTest {

2. public static void main(String [] args)

3. System.out.print("1 ");

4. synchronized(args){

5. System.out.print("2 ");

6. try {

8. }

10. }

12. }

what is the result of trying to compile and run this program?

1. 
   It will fail to compile because it has to be synchronized on the this object.
   
2. 
   1 2
   
3. 
   1 2 3
   
4. 
   1 3
   
5. 
   It fails to compile because the IllegalMonitorStateException of wait() is not dealt with in line 7.
   
6. 
   At runtime, it throws an IllegalMonitorStateException when trying to wait.
   

Given the following,

11. x = 0;

12. if (x1.hashCode() != x2.hashCode() ) x = x + 1;

13. if (x3.equals(x4) ) x = x + 10;

14. if (!x5.equals(x6) ) x = x + 100;

15. if (x7.hashCode() == x8.hashCode() ) x = x + 1000;

16. System.out.println("x = " + x);

and assuming that the equals () and hashCode() methods are property implemented, if the output is “x = 1111”, which of the following statements will always be true?

1. 
   x5.hashCode()
   
2. 
   x3.hashCode()
   
3. 
   x8.equals(x7)
   
4. 
   x2.equals(x1)
   

Given the following,

12. TreeSet map = new TreeSet();

13. map.add("one");

14. map.add("two");

15. map.add("three");

16. map.add("four");

17. map.add("one");

18. Iterator it = map.iterator();

19. while (it.hasNext() ) {

20. System.out.print( it.next() + " " );

21. }

1. 
   one four three two one
   
2. 
   one two three four one
   
3. 
   four one three two
   
4. 
   four three two one
   
5. 
   The print order is not guaranteed.
   
6. 
   one two three four
   

Given the following,

12. void doStuff3() {

13. X x = new X();

14. X y = doStuff(x);

15. y = null;

16. x = null;

17. }

19. return doStuff2(mx);

20. }

at what point is the object created in line 13 eligible for garbage collection?

1. 
   It is not possible to know for sure.
   
2. 
   After line 15 runs
   
3. 
   After line 16 runs
   
4. 
   After line 17 runs
   
5. 
   The object is not eligible.
   

Given the following,

12. X3 x2 = new X3();

13. X3 x3 = new X3();

14. X3 x5 = x3;

15. x3 = x2;

16. X3 x4 = x3;

17. x2 = null;

18. // insert code

what two lines of code, inserted independently at line 18, will make an object eligible for garbage collection? (Choose two.)

1. 
   x3 = null;
   
2. 
   x4 = null;
   
3. 
   x5 = null;
   
4. 
   x3 = x4;
   
5. 
   x5 = x4;
   

Given the following,

class MyThread extends Thread {

MyThread() {

System.out.print(" MyThread");

}

public void run() {

}

public void run(String s) {

}

}

public static void main (String [] args) {

Thread t = new MyThread() {

public void run() {

System.out.println(" foo");

}

};

}

}

1. 
   MyThread foo
   
2. 
   bar foo
   
3. 
   foo
   
4. 
   MyThread bar
   
5. 
   foo bar
   
6. 
   foo bar baz
   

Given the following,

class Test1 {

public int value;

public int hashCode() { return 42; }

}

class Test2 {

public int hashcode() { return (int)(value^5); }

}

which statement is true?

1. 
   The Test1 hashCode() method is more efficient than the Test2 hashCode() method.
   
2. 
   The Test1 hashCode() method is less efficient than the Test2 hashCode() method.
   
3. 
   The two hashcode() methods will have the same efficiency.
   
4. 
   class Test1 will not compile.
   
5. 
   class Test2 will not compile.
   

Given the following,

public class SyncTest {

public static void main (String [] args) {

Thread t = new Thread() {

Foo f = new Foo();

public void run() {

f.increase(20);

}

};

t.start();

}

class Foo {

public void increase(int amt) {

int x = data;

data = x + amt;

}

}

and assuming that data must be protected from corruption, what—if anything—can you add to the preceding code to ensure the integrity of data?

1. 
   Synchronize the increase() method
   
2. 
   Wrap a synchronize(this) around the call to f.increase().
   
3. 
   Synchronize the run method.
   
4. 
   The existing code will cause a runtime exception.
   
5. 
   The existing code will not compile.
   
6. 
   Put in a wait() call prior to invoking the increase() method.
   

Given the following class:

class Counter {

public int startHere = 1;

public int endHere = 100;

public static void main(String[] args) {

new Counter().go();

}

void go() {

Thread t = new Thread(a);

t.start();

}

}

Select all valid answers.

a) Runable a = new Runable(){

public void run() {

for (int i = startHere; i <= endHere; i++) { System.out.println(i); }

}

} ;

public void run() {

for (int i = startHere; i <= endHere; i++) { System.out.println(i); }

}

} ;

public void run() {

for (int i = startHere; i <= endHere; i++) { System.out.println(i);}

}

} ;

Given the following class:

class Counter {

public static void main(String[] args) {

Thread t = new Thread(new CounterBehavior());

t.start();

}

}

Which of the following is a valid definition of CounterBehavior that would make Counter's main() method count from 1 to 100, counting once per second?

static class CounterBehavior implements Runnable {

public void run() {

try{

System.out.println(i);

Thread.sleep(1 000);

}

} catch (InterruptedException x) { }

}

b) This class is an inner class to Counter:

public void run() {

for (int i = 1; i <= 100; i++); try{

System.out.println(i);

Thread.sleep(1 000);

} catch (InterruptedException x) {}

}

}

}

class CounterBehavior {

for (int i = 1: i <= 100: i++):

try{

Thread.sleep(1 000);

} catch (InterruptedException x) { }

}

}

Given the following class:

class Counter {

public static void main(String[] args) {

Thread t = new Thread(new CounterBehaviorQ); t.startQ;

}

}

a) This class is a top-level class:

static class CounterBehavior implements Runnable { public void

run() {

for(int i=1;i<= 100; i++) {

System.out.println(i);

Thread.sleep(1 000);

}

} catch (InterruptedException x) { }

}

b) This class is an inner class to Counter:

public void run() {

for (int i= 1;i<= 1000;i++);

try{

Thread.sleep(1 000);

} catch (InterruptedException x) {}

}

}

c) This class is an inner class to Counter:

class CounterBehavior {

for (int i = 1; i <= 100; i++);

try{

System.out.println(i);

} catch (InterruptedException x) { }

}

}

Question 123–a

class C1 {};

class C2 extends C1 {};

class C3 extends C1 {};

C2 c2 = new C2();

C3 c3 = new C3();

Analyze the following statement:

c2 = (C2)((C1)c3);

1. 
   You will get a runtime error because you cannot cast objects from sibling classes.
   
2. 
   c3 is cast into c2 successfully.
   
3. 
   You will get a runtime error because the Java runtime system cannot perform multiple casting in nested form.
   
4. 
   The statement is correct.
   

Given the following class definition:

class A {

protected int i;

A(int i) {

this.i = i;

}

}

Which of the following would be a valid inner class for this class?

a) class B {

B()

System.out.println("i = "+ i);

}

b) class B extends A {

c) class A {

}

d) class B {

e) class B {

class A {

}

}

Given the following code:

class C1 {}

class C2 extends C1 { }

class C3 extends C2 { }

class C4 extends C1 {}

C1 c1 = new C1();

C2 c2 = new C2();

C3 c3 = new C3();

C4 c4 = new C4();

Which of the following expressions evaluates to false?

1. 
   c3 instanceof C1
   
2. 
   c4 instanceof C2
   
3. 
   c2 instanceof C1
   
4. 
   c1 instanceof C1
   

Given the following code:

import java.awt.*;

public class SetF extends Frame {

public static void main(String argv[]) {

SetF s=new SetF();

s.setSize(300,200);

s.setVisible(true);

}

}

How could you set the frame surface color to pink?

1. 
   s.setColor(P1NK);
   
2. 
   s .Background(pink);
   
3. 
   s.color=Color.pink;
   
4. 
   s.setBackground(Color.pink);
   

Given the following code, find the syntax error?

public class Test {

public static void main(String[] args) {

m(new GraduateStudent());

m(new Student());

m(new Person());

m(new Object());

}

public static void m(Student x) {

}

}

}

class Student extends Person {

return "Student";

}

}

class Person extends Object {

return "Person";

}

}

1. 
   m(new Object()) causes an error
   
2. 
   m(new Student()) causes an error
   
3. 
   m(new GraduateStudent()) causes an error
   
4. 
   m(new Person()) causes an error
   

Given the following code, what will be the output?

class Value

{

public int i = 15;

public class Test

{

public static void main(String argv[])

Test t = new Test();

t.first();

}

public void first()

int i = 5;

Value v = new Value();

v.i = 25;

second(v, i);

System.out.println(v.i);

}

public void second(Value v, int i)

i = 0;

Value val = new Value();

v = val;

System.out.println(v.i + " " + i);

}

} // Test

20

b) 15 0

c) 15 0

d) 20 0

Given the following code what will be output?

public class Pass{

static int j=20;

public static void main(String argv[]) {

int i=10;

Pass p = new Pass();

p.amethod(i);

System.out.println(i);

System.out.println(j);

}

public void amethod(int x) {

j=j*2

}

1. 
   10 and 40
   
2. 
   Error: amethod parameter does not match variable
   
3. 
   10 and 20
   
4. 
   20 and 40
   

Given the following program, which statements are guaranteed to be true?

public class ThreadedPrint {

static Thread makeThread(final String id, boolean daemon) {

Thread t = new Thread(id) {

public void run() {

System.out.println(id);

}

};

t.start();

return t;

}

public static void main(String[] args) {

Thread b = makeThread("B", true);

System.out.print("End\n");

}

}

1. 
   The letter A is always printed.
   
2. 
   The letter A is never printed after End.
   
3. 
   The letter B is never printed after End.
   
4. 
   The letter B is always printed.
   
5. 
   The program might print B, End and A, in that order.
   

Given this interface definition:

interface A {

int method 1 (int i);

int method2(int j);

}

which of the following class implement this interface and is not abstract?

int methodl(int i) { }

int method2(intj) { }

}

b) class B implements A {

int method2() { }

}

c) class B implements A {

int method2(intj) { }

}

d) class B implements A

int methodl(int i) { }

}

e) class B {

int method2(intj) { }

}

Question 132–bc

Here is part of the code for a class that implements the Runnable interface:

1. public class Whiffler extends Object

implements Runnable {

2. Thread myT ;

3. public void start(){

4. myT = new Thread( this );

5. }

7. while( true ){

8. doStuff();

9. }

11. }

Assume that the rest of the class defines doStuff, and so on, and that the class compiles without error. Also assume that a Java application creates a Whiffler object and calls the Whiffler start method, that no other direct calls to Whiffler methods are made, and that the thread in this object is the only one the application creates. Which of the following are correct statements? [Check all correct answers.]

1. 
   The doStuff method will execute at least one time.
   
2. 
   The statement in line 10 will never be reached.
   
3. 
   The doStuff method will never be executed.
   
4. 
   The doStuff method will be called repeatedly.
   

How can a class that is run as a thread be defined?

1. 
   By implementing the Runnable interface.
   
2. 
   By subclassing the Thread class.
   
3. 
   By implementing the Multithread interface.
   
4. 
   By implementing the Throwable interface.
   

How do Swing menus differ from AWT menus?

1. 
   Swing menus are implemented in separate windows.
   
2. 
   None of the other answers
   
3. 
   Swing menus are round.
   
4. 
   Swing menus are components.
   

How can you remove an element from a Vector?

1. 
   clear method
   
2. 
   remove method
   
3. 
   delete method
   
4. 
   cancel method
   

How is the ternary operator written?

1. 
   y : x ? z
   
2. 
   x : y ? z
   
3. 
   ? x y : z
   
4. 
   x ? y : z
   

How many frames are displayed?

import javax.swing.*;

public class Test extends JFrame {

public static void main(String[] args) {

JFrame f1 = new Test();

JFrame f2 = new Test();

JFrame f3 = new Test();

f1.setVisible(true);

f2.setVisible(true);

f3.setVisible(true);

}

}

1. 
   1
   
2. 
   2
   
3. 
   4
   
4. 
   3
   
5. 
   6
   
6. 
   5
   

_____________ is a formal process that seeks to understand the problem and document in detail what the software system needs to do.

1. 
   Testing
   
2. 
   Analysis
   
3. 
   Implementation
   
4. 
   Design
   
5. 
   Requirements specification
   

_________ is a general binary relationship that describes an activity between two objects.

1. 
   Aggregation
   
2. 
   Association
   
3. 
   Inheritance
   
4. 
   Composition
   

__________ is a special form of association that represents an ownership relationship between two objects.

1. 
   Composition
   
2. 
   Association
   
3. 
   Aggregation
   
4. 
   Inheritance
   

I want a method of class Y to have access to a variable inside class X. If Y doesn’t extend X, what visibility must I give to that variable:

1. 
   public
   
2. 
   private
   
3. 
   none of the others
   
4. 
   protected
   
5. 
   static
   

If a method is defined as public, then we can use it

1. 
   both in the class in which it is defined and in all other classes
   
2. 
   only in the method in which it is defined
   
3. 
   only in other classes, but not in the class in which it is defined
   
4. 
   only in the class in which it is defined
   

If the following HTML code is used to display the applet in the code

MgAp what will be displayed at the console?

parameter HowOld=30>

import j ava.applet. *;

import java.awt.*;

public class MgAp extends Applet{

public void init() {

System.out.println(getParameter("age"));

}

}

1. 
   0
   
2. 
   30
   
3. 
   null
   
4. 
   Error: no such parameter
   

If we define data as "int [] data = new int[10];". What is the result of this definition?

1. 
   data[i] = null, that is, all elements of data are initialized to null, i is the index of elements
   
2. 
   data[i] = 0.0, that is, all elements of data are initialized to 0.0,i is the index of elements
   
3. 
   data[i] = 0, that is, all elements of data are initialized to 0, i is the index of elements
   
4. 
   data = null
   

If you compile code for a multiclass program consisting of a main class and two helper classes, how many .class files will be produced?

1. 
   Three
   
2. 
   One
   
3. 
   Two
   
4. 
   Zero
   

If you define more than one Java class in the same source file, how many of these classes can be public?

1. 
   Only one of the multiple classes can be public.
   
2. 
   None; in a multiclass file, all classes must be private or protected.
   
3. 
   Any or all classes can be public.
   

If you run the code below, what gets printed out?

String s=new String("Bicycle");

int iBegin=1;

char iEnd=3;

System.out.println(s.substring(iBegin,iEnd));

1. 
   icy
   
2. 
   error: no method matching substring(int,char)
   
3. 
   Bic
   
4. 
   ic
   

If you want to store non-duplicated objects in the order in which they are inserted, you should use ___.

1. 
   LinkedList
   
2. 
   LinkedHashSet
   
3. 
   ArrayList
   
4. 
   HashSet
   
5. 
   TreeSet
   

In a linked list, each element references both the preceding and succeeding elements.

1. 
   false
   
2. 
   true
   

In a scrollable and updateable result set, you can use ___________ methods on a result set.

1. 
   insertRow()
   
2. 
   deleteRow()
   
3. 
   last()
   
4. 
   first()
   
5. 
   updateRow()
   

In Java programming, which term describes converting information (such as a variable or object) into a new form?

1. 
   transforming
   
2. 
   casting
   
3. 
   compiling
   
4. 
   integrating
   

In Java, what is a compilation unit?

1. 
   A part of the Java compiler
   
2. 
   A combination of source code and data files
   
3. 
   A Java source code file
   
4. 
   A unit of data that cannot be changed
   

In object-oriented programming, what term refers to the capability of objects to have many methods of the same name, but with different types of arguments.

1. 
   Polymorphism
   
2. 
   Late binding
   
3. 
   Encapsulation
   
4. 
   Inheritance
   

In order for a source code file containing the public class Test to successfully compile, which of the following must be true?

1. 
   It must declare a package named Test.
   
2. 
   It must import java.lang.
   
3. 
   It must have a package statement.
   
4. 
   It must be named Test.java.
   

In order for the MyProgram class to be compiled and run, which of the following must be true?

1. 
   MyProgram must have a correctly formed main() method.
   
2. 
   MyProgram.java must include a package statement.
   
3. 
   MyProgram class must be declared public.
   
4. 
   MyProgram must import java.lang.
   

In order for the public class MyClass to successfully compile, which of the following are true?

1. 
   MyClass must be defined in the file MyClass.java.
   
2. 
   MyClass must be defined in the MyClass package.
   
3. 
   MyClass must have a correctly formed main() method.
   
4. 
   MyClass must be imported.
   

In the following code, what is the scope of local variable x?

Line 1: public class SunTest extends Animator{

Line 2: private Sun theSun = new Sun();

Line 3: public void draw(Graphics g){

Line 4: int diameter = 40;

Line 5: int x = 10;

Line 6: theSun.draw(g, x, diameter);

Line 7: } //end of draw method

Line 8: }//end of class SunTest

1. 
   Line 3-7, the whole draw method
   
2. 
   Line 5-7, after x is defined in the draw method
   
3. 
   Line 1-8, the SunTest class
   
4. 
   Line 4-7, after diameter is defined in the draw method
   

In the standard Java classes such as java.awt.Component, what does awt stand for?

1. 
   Ancestor Windowing Tools
   
2. 
   Active Workshop Tools
   
3. 
   Abstract Window Toolkit
   
4. 
   Absolute Window Template
   

Insert code into the equalsImpl() method in order to provide a correct implementation of the equals() method.

public class Pair {

int a, b;

public Pair(int a, int b) {

this.a = a;

this.b = b;

}

public boolean equals(Object o) {

}

private boolean equalsImpl(Pair o) {

}

}

1. 
   return a == o.a;
   
2. 
   return false;
   
3. 
   return a == o.a || b == o.b;
   
4. 
   return a == o.a & b == o.b;
   
5. 
   return a >= o.a;
   

Interface _______ helps manage the connection between the Java program and the database.

1. 
   Connection.
   
2. 
   ResultSet
   
3. 
   Statement.
   
4. 
   java.sql
   

JDBC is

1. 
   Java Database Connectivitive
   
2. 
   Java's database applet interface
   
3. 
   Java's event delegation model
   
4. 
   Java's remote relational database interface
   
5. 
   Java's persistent object interface
   

Line 12 of the code for the Point3D class sets the object variable z to what value?

11: public void move(int x, int y, int z) {

12: this.z = z;

13: super.move(x, y);

14: }

1. 
   whatever argument is sent in line 11
   
2. 
   the value of z from the Point class
   
3. 
   the value of z set when z was defined
   

__________ models the is-a relationship between two classes.

1. 
   Composition
   
2. 
   Inheritance
   
3. 
   Aggregation
   
4. 
   Association
   

Non-modal dialog boxes must be closed before control returns to the window that launched them.

1. 
   false
   
2. 
   true
   

Objects...

1. 
   Are instances of classes, and accessed through special variables known as object references
   
2. 
   Always hold decimal values in the format of "2.4"
   
3. 
   Cannot be used to represent real world objects.
   
4. 
   Are a type of class.
   

Object-oriented programming allows more complex objects to be constructed from basic building blocks that are available in class libraries. What is this basic capability of object-oriented programming called?

1. 
   Polymorphism
   
2. 
   Object reuse
   
3. 
   Encapsulation
   
4. 
   Late binding
   

Object-oriented programming allows you to derive new classes from existing classes. This is called ____________.

1. 
   generalization
   
2. 
   inheritance
   
3. 
   abstraction
   
4. 
   encapsulation
   

11. public static void main(String[]args){

12. Object obj=new Object(){

13. public int hashCode(){

14. return 42;

15. }

17. System.out.println(obj.hashCode());

18. }

What is the result?

1. 
   Compilation fails because of an error on line 16.
   
2. 
   Compilation fails because of an error on line 12.
   
3. 
   An exception is thrown at runtime.
   
4. 
   42
   
5. 
   Compilation fails because of an error on line 17.
   

Platform Independence refers to:

1. 
   Inheritance Hierarchies in the Exception class
   
2. 
   Ability to run the same final code on different Operating Systems
   
3. 
   Operating System/Object interface
   
4. 
   Classes derived from Throwable.
   

public class MyClass {

public static void main(String argv[]) { }

/*Modifier at XX */ class Mylnner {}

}

What modifiers would be legal at XX in the above code?

1. 
   friend
   
2. 
   static
   
3. 
   public
   
4. 
   private
   

__________ represents the roles the object plays. The objects at the top of the diagram represent class roles.

1. 
   Activation
   
2. 
   Method invocation
   
3. 
   Class role
   
4. 
   Lifeline
   

_______________ returns the selected item on a JComboBox jcbo.

1. 
   jcbo.getSelectedIndices()
   
2. 
   jcbo.getSelectedIndex()
   
3. 
   jcbo.getSelectedItem()
   
4. 
   jcbo.getSelectedItems()
   

Result set meta data are retieved through ____________.

1. 
   a PreparedStatement object
   
2. 
   a Statement object
   
3. 
   a ResultSet Object
   
4. 
   a Connection object
   

Select ALL correct ways to calculate the sum of the first n even

numbers (that is, 2 + 4 + 6 + ... + 2*n)

a) int sum = 0;

for( int i = 1; i<=2*n; i+=1){

if(i / 2 == 0){

sum += i;

}

}

for (int i=2; i<=2*n; i+=2) {

sum += i;

}

c) int sum = 0;

while(i%2== 0 & i<= 2n){

sum += i;

}

d) int sum = 0;

if(i % 2 == 0){

sum += i;

}

}

Select four. Suppose that classes X and Y are subclasses of Z and Z implements the W interface. Which of the following casting statements are true?

1. 
   A reference to an object of class X can be cast to a reference to an object of class Y.
   
2. 
   A reference to an object of class X can be cast to a reference to an object of class Z.
   
3. 
   A reference to an object of class Y can be cast to a reference to an object of class X.
   
4. 
   A reference to an object of class X can be cast to a reference to an object of interface W.
   
5. 
   A reference to an object of class Y can be cast to a reference to an object of interface W.
   
6. 
   A reference to an object of class Y can be cast to a reference to an object of class Z.
   

Select four. Which of the following are Container classes?

1. 
   Dialog
   
2. 
   Scrollbar
   
3. 
   Applet
   
4. 
   Panel
   
5. 
   MenuBar
   
6. 
   FileDialog
   

Select three. Consider the Label() constructors shown here. Which of the following are valid examples?

1. 
   new Label('Default Label', Label.LEFT)
   
2. 
   new Label("Default Label", LEFT)
   
3. 
   new Label()
   
4. 
   new Label("Default Label", "Label.CENTER")
   
5. 
   new Label("Default Label")
   
6. 
   new Label("Default Label", Label.RIGHT)
   

Select three correct statements.

1. 
   A static method cannot override a non-static method
   
2. 
   A synchronized method cannot be overridden
   
3. 
   A non-static method cannot override a static method
   
4. 
   A non-static method may be overloaded by a static method
   
5. 
   A static method may override another static method
   

Select two. Which of the following are characteristic of a fully encapsulated class?

1. 
   All methods are private.
   
2. 
   Methods are provided to access the class's properties.
   
3. 
   The class's design cannot be changed without impact on its implementation.
   
4. 
   All variables are private.
   

Select two. Which of the following are the direct subclasses of MenuComponent class?

1. 
   PopupMenu
   
2. 
   Menu
   
3. 
   MenuItem
   
4. 
   MenuBar
   

Select two. Which of the following are valid Java comments?

1. 
   /** This is a comment. */
   
2. 
   /* This is a comment. */
   
3. 
   \* This is a comment *\
   
4. 
   \\ This is a comment.
   

Select two. Which of the following are valid main() methods?

a) public static void main(String []args) { }

b) public static void main() { }

c) public static void main(String[] args) { }

d) void main(String[] args) { }

Select two. Which of the following casting statements are true?

1. 
   A reference to an array can be cast to a reference to a String.
   
2. 
   A reference to an array can be cast to a reference to an Object.
   
3. 
   A reference to an array can be cast to a reference to a Cloneable.
   

Select two. Which of the following methods will cause a Frame to be displayed?

1. 
   show()
   
2. 
   display()
   
3. 
   displayFrame()
   
4. 
   setVisible()
   

Show the output of running the class Test in the following code lines:

interface A {

}

class C {

class B extends D implements A {

}

public class Test extends Thread {

B b = new B();

if (b instanceof A)

System.out.println("b is an instance of A");

if (b instanceof C)

System.out.println("b is an instance of A");

if (b instanceof C)

System.out.println("b is an instance of C");

}

}

class D extends C {

1. 
   b is an instance of C.
   
2. 
   Nothing.
   
3. 
   b is an instance of A followed by b is an instance of C.
   
4. 
   b is an instance of A.
   

Suppose A is an interface, B is a concrete class with a default constructor that implements A. Which of the following is correct?

1. 
   B b = new B();
   
2. 
   A a = new B();
   
3. 
   B b = new A();
   
4. 
   A a = new A();
   

Suppose a Panel is added to a Frame and a Button is added to the Panel. If the Frame's font is set to 12-point TimesRoman, the Panel's font is set to 10-point TimesRoman, and the Button's font is not set, what font will be used to display the Button's label?

1. 
   12-point TimesRoman
   
2. 
   10-point TimesRoman
   
3. 
   11-point TimesRoman
   
4. 
   9-point TimesRoman
   

Suppose that an existing legacy database supports ODBC but not JDBC. Which technologies may be used to access the database from a Java applet?

1. 
   JNDI
   
2. 
   JDBC and ODBC-capable database middleware
   
3. 
   The Java-ODBC bridge driver
   
4. 
   JNI
   

Suppose that you want to have an object EEHH handle the TextEvent of a TextArea object TTT. How should you add EEHH as the event handler for TTT?

1. 
   addTextListener(EEHH,TTT);
   
2. 
   TTT.addTextListener(EEHH);
   
3. 
   EEHH.addTextListener(TTT);
   
4. 
   addTextListener(TTT,EEHH);
   

Suppose we try to compile and run the following:

public class TechnoSample {

public static void main (String[] args){

int j ;

for( int i = 10, j = 0 ; i > j ; j++ ){

i = i - 1 ;

}

// Statement can go here

}

Which of the following statements about this code are correc

1. 
   The loop initializer uses the correct form to set the values of i and j
   
2. 
   The loop initializer is not legal and the code will not compile for that reason
   
3. 
   If we put the following statement after the loop, it would report "j = 5"
   
4. 
   System.out.println( "j = " + j );
   
5. 
   If we put the following statement after the loop, it would report "i = 5 j = 5"
   
6. 
   System.out.println("i = " + i + " j = " + j );
   

Suppose you create a class Cylinder to be a subclass of Circle.

Analyze the following code:

class Cylinder extends Circle {

double length;

Cylinder(double radius) {

Circle(radius);

}

}

1. 
   The program compiles fine, but you cannot create an instance of Cylinder because the constructor does not specify the length of the cylinder.
   
2. 
   The program has a syntax error because you attempted to invoke the Circle class's constructor illegally.
   
3. 
   The program compiles fine, but it has a runtime error because of invoking the Circle class's constructor illegally.
   

The component that processes the listener is called ___________.

1. 
   the adapter object
   
2. 
   the source object
   
3. 
   the listener object
   
4. 
   the adaptee object
   

The EventObject class and the EventListener interface are empty and do not declare any methods.

1. 
   true
   
2. 
   false
   

The 'extends' keyword in a class declaration:

1. 
   Specifies the parent class to the class
   
2. 
   Specifies that the class has abstract methods
   
3. 
   Sets the default access privileges for the class
   
4. 
   Allocates more memory space for the class
   

The following block of code creates a Thread using a Runnable target:

Runnable target = new MyRunnable();

Thread myThread = new Thread(target);

Which of the following classes can be used to create the target, so that the preceding code compiles correctly?

1. 
   public class MyRunnable extends Object{public void run(){}}
   
2. 
   public class MyRunnable extends Runnable{public void run(){}}
   
3. 
   public class MyRunnable implements Runnable{void run(){}}
   
4. 
   ic class MyRunnable implements Runnable{public void start(){}}
   
5. 
   public class MyRunnable implements Runnable{public void run(){}}
   

The following code has a nested class named Nested. What is the proper format to declare and create an instance of Nested in the main method?

1 public class TopLevel {

2

3 public static void main (String[] args){

5 System.out.println("Created " + nt );

6 }

7

8 static class Nested {

10 Nested( String s ){ id = s ; }

11 } // end Nested

12 }

1. 
   Nested nt = new Nested("one");
   
2. 
   Nested nt = new TopLevel().new Nested("three");
   
3. 
   TopLevel.Nested nt = new Nested("two");
   
4. 
   TopLevel.Nested nt = new TopLevel().new Nested("four");
   

The following code will print:

1: Double a = new Double(Double.NaN);

2: Double b = new Double(Double.NaN);

3:

4: if( Double.NaN == Double.NaN )

6: else

8:

9: if( a.equals(b) )

11: else

a) False

b) True

c) True

d) False

The interface __________ should be implemented to listen for a button action event.

1. 
   MouseListener
   
2. 
   ContainerListener
   
3. 
   WindowListener
   
4. 
   ActionListener
   
5. 
   FocusListener
   

The listener's method __________ is invoked when a mouse button is released.

1. 
   public void mouseClicked(MouseEvent e)
   
2. 
   public void mouseEntered(MouseEvent e)
   
3. 
   public void mouseExited(MouseEvent e)
   
4. 
   public void mousePressed(MouseEvent e)
   
5. 
   public void mouseReleased(MouseEvent e)
   

The method in the ActionEvent __________ returns the action command of the button.

1. 
   getID()
   
2. 
   paramString()
   
3. 
   getActionCommand()
   
4. 
   getModifiers()
   

The relationship between an interface and the class that implements it is

1. 
   None
   
2. 
   Association
   
3. 
   Inheritance
   
4. 
   Aggregation
   

The setEditable() method is used to set a text object to the read-only state

1. 
   false
   
2. 
   true
   

The size of a linked list is _______________.

1. 
   Able to get bigger, but not smaller
   
2. 
   Not able to get bigger or smaller
   
3. 
   Able to get bigger and smaller
   
4. 
   Able to get smaller, but not bigger
   

The statements in a Java program are executed…

1. 
   From the top down starting at a preset or predictable location.
   
2. 
   From the bottom up.
   
3. 
   From the top down.
   
4. 
   From the top down starting at a random location.
   

The visibility of these modifiers increases in this order:

1. 
   none (if no modifier is used), protected, private, and public.
   
2. 
   private, protected, none (if no modifier is used), and public.
   
3. 
   none (if no modifier is used), private, protected, and public.
   
4. 
   private, none (if no modifier is used), protected, and public.
   

Traverse the tree with postorder

1. 
   D B G I E F C H A
   
2. 
   D B G I H E F C A
   
3. 
   D B G I E H F C A
   
4. 
   D B G H E I F C A
   

To create a statement on a Connection object conn, use

1. 
   Statement statement = conn.statement();
   
2. 
   Statement statement = conn.createStatement();
   
3. 
   Statement statement = connection.create();
   
4. 
   Statement statement = Connection.createStatement();
   

To detect whether the right button of the mouse is pressed, you use the method __________ in the MouseEvent object evt.

1. 
   evt.isControlDown()
   
2. 
   evt.isAltDown()
   
3. 
   evt.isShiftDown()
   
4. 
   evt.isMetaDown()
   

To enable a component to listen to keyboard events, you need to ____

1. 
   All of the other answers
   
2. 
   Override the isFocusTraversable method defined in the Component class to return true.
   
3. 
   Invoke the component’s requestFocus method to set focus on this component.
   
4. 
   Implement the KeyListener interface for the component.
   

To execute a SELECT statement "select * from Address" on a Statement object stmt, use

1. 
   stmt.executeQuery("select * from Address");
   
2. 
   stmt.query("select * from Address");
   
3. 
   stmt.execute("select * from Address");
   
4. 
   stmt.executeUpdate("select * from Address");
   

To find a maximum object in an array of

strings (e.g., String[] names = {"red", "green", "blue"}), use

1. 
   None of the other answers
   
2. 
   Arrays.sort(names)
   
3. 
   Collections.max(Arrays.asList(names))
   
4. 
   Collections.max(names)
   
5. 
   Arrays.max(names)
   

To get an iterator from a set, you may use the __________ method.

1. 
   findIterator
   
2. 
   iterators
   
3. 
   iterator
   
4. 
   getIterator
   

To listen to mouse movement events, the listener must implement the __________ interface.

1. 
   ComponentListener()
   
2. 
   MouseMotionListener()
   
3. 
   MouseListener()
   
4. 
   WindowListener()
   

To obtain a scrollable or updateable result set, you must first create a statement using the following syntax:

1. 
   Statement statement = connection.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_UPDATABLE);
   
2. 
   Statement statement = connection.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_UPDATABLE);
   
3. 
   Statement statement = connection.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_READ_ONLY);
   
4. 
   Statement statement = connection.createStatement(ResultSet.TYPE_FORWARD_ONLY, ResultSet.CONCUR_READ_ONLY);