Sun Certified Java Developer (SCJD) Interview Questions

 
1.
Explain Given: 11. abstract class Vehicle { public int speed() { return 0; } 12. class Car extends Vehicle { public int speed() { return 60; } 13. class RaceCar extends Car { public int speed() { return 150; } ... 21. RaceCar racer = new RaceCar(); 22. Car car = new RaceCar(); 23. Vehicle vehicle = new RaceCar(); 24. System.out.println(racer.speed() + ", " + car.speed() 25. + ", " + vehicle.speed()); What is the result? A. 0, 0, 0 B. 150, 60, 0 C. Compilation fails. D. 150, 150, 150 E. An exception is thrown at runtime.
2.
Explain Given: 1. public class Threads2 implements Runnable { 2. 3. public void run() { 4. System.out.println("run."); 5. throw new RuntimeException("Problem"); 6. } 7. public static void main(String[] args) { 8. Thread t = new Thread(new Threads2()); 9. t.start(); 10. System.out.println("End of method."); 11. } 12. } Which two can be results? (Choose two.) A. java.lang.RuntimeException: Problem B. run. java.lang.RuntimeException: Problem C. End of method. java.lang.RuntimeException: Problem D. End of method. run. java.lang.RuntimeException: Problem E. run. java.lang.RuntimeException: Problem End of method.
3.
Suppose A team of programmers is reviewing a proposed API for a new utility class. After some discussion, they realize that they can reduce the number of methods in the API without losing any functionality. If they implement the new design, which two OO principles will they be promoting? A. Looser coupling B. Tighter coupling C. Lower cohesion D. Higher cohesion E. Weaker encapsulation F. Stronger encapsulation
4.
Explain Given: 11. public static void parse(String str) { 12. try { 13. float f = Float.parseFloat(str); 14. } catch (NumberFormatException nfe) { 15. f = 0; 16. } finally { 17. System.out.println(f); 18. } 19. } 20. public static void main(String[] args) { 21. parse("invalid"); 22. } What is the result? A. 0.0 B. Compilation fails. C. A ParseException is thrown by the parse method at runtime. D. A NumberFormatException is thrown by the parse method at runtime.
5.
Explain Given: 11. public abstract class Shape { 12. private int x; 13. private int y; 14. public abstract void draw(); 15. public void setAnchor(int x, int y) { 16. this.x = x; 17. this.y = y; 18. } 19. } Which two classes use the Shape class correctly? (Choose two.) A. public class Circle implements Shape { private int radius; } B. public abstract class Circle extends Shape { private int radius; } C. public class Circle extends Shape { private int radius; public void draw(); } D. public abstract class Circle implements Shape { private int radius; public void draw(); } E. public class Circle extends Shape { private int radius; public void draw() {/* code here */} F. public abstract class Circle implements Shape { private int radius; public void draw() { /* code here */ }
6.
Explain What is the result of mounting a file system with thenoatimeoption enabled? A.It enables the UFS logging B.It disables the update of file access times C.It prevents the creation of files larger than 2Gbytes D.It prevents the user from updating the file modification times
7.
Can you explain Given: 5. class Building { } 6. public class Barn extends Building { 7. public static void main(String[] args) { 8. Building build1 = new Building(); 9. Barn barn1 = new Barn(); 10. Barn barn2 = (Barn) build1; 11. Object obj1 = (Object) build1; 12. String str1 = (String) build1; 13. Building build2 = (Building) barn1; 14. } 15. } Which is true? A. If line 10 is removed, the compilation succeeds. B. If line 11 is removed, the compilation succeeds. C. If line 12 is removed, the compilation succeeds. D. If line 13 is removed, the compilation succeeds. E. More than one line must be removed for compilation to succeed.
8.
Explain Which Man class properly represents the relationship "Man has a best friend who is a Dog"? A. class Man extends Dog { } B. class Man implements Dog { } C. class Man { private BestFriend dog; } D. class Man { private Dog bestFriend; } E. class Man { private Dog; } F. class Man { private BestFriend; }
9.
Explain Given: 1. package test; 2. 3. class Target { 4. public String name = "hello"; 5. } What can directly access and change the value of the variable name? A. any class B. only the Target class C. any class in the test package D. any class that extends Target
10.
Explain Given: 1. public class Threads4 { 2. public static void main (String[] args) { 3. new Threads4().go(); 4. } 5. public void go() { 6. Runnable r = new Runnable() { 7. public void run() { 8. System.out.print("foo"); 9. } 10. }; 11. Thread t = new Thread(r); 12. t.start(); 13. t.start(); 14. } 15. } What is the result? A. Compilation fails. B. An exception is thrown at runtime. C. The code executes normally and prints "foo". D. The code executes normally, but nothing is printed.
11.
Explain Given: 11. public class Rainbow { 12. public enum MyColor { 13. RED(0xff0000), GREEN(0x00ff00), BLUE(0x0000ff); 14. private final int rgb; 15. MyColor(int rgb) { this.rgb = rgb; } 16. public int getRGB() { return rgb; } 17. }; 18. public static void main(String[] args) { 19. // insert code here 20. } 21. } Which code fragment, inserted at line 19, allows the Rainbow class to compile? A. MyColor skyColor = BLUE; B. MyColor treeColor = MyColor.GREEN; C. if(RED.getRGB() < BLUE.getRGB()) { } D. Compilation fails due to other error(s) in the code. E. MyColor purple = new MyColor(0xff00ff); F. MyColor purple = MyColor.BLUE + MyColor.RED;
12.
Explain Given: 1. class Super { 2. private int a; 3. protected Super(int a) { this.a = a; } 4. } ... 11. class Sub extends Super { 12. public Sub(int a) { super(a); } 13. public Sub() { this.a = 5; } 14. } Which two, independently, will allow Sub to compile? (Choose two.) A. Change line 2 to: public int a; B. Change line 2 to: protected int a; C. Change line 13 to: public Sub() { this(5); } D. Change line 13 to: public Sub() { super(5); } E. Change line 13 to: public Sub() { super(a); }
13.
Explain Which two statements are true? (Choose two.) A. It is possible for more than two threads to deadlock at once. B. The JVM implementation guarantees that multiple threads cannot enter into a deadlocked state. C. Deadlocked threads release once their sleep() methods sleep duration has expired. D. Deadlocking can occur only when the wait(), notify(), and notifyAll() methods are used incorrectly. E. It is possible for a single-threaded application to deadlock if synchronized blocks are used incorrectly. F. If a piece of code is capable of deadlocking, you cannot eliminate the possibility of deadlocking by inserting invocations of Thread.yield().
14.
Tell me What is native keyword and abstract keyword?
15.
Explain Given: 1. public class Blip { 2. protected int blipvert(int x) { return 0; } 3. } 4. class Vert extends Blip { 5. // insert code here 6. } Which five methods, inserted independently at line 5, will compile? (Choose five.) A. public int blipvert(int x) { return 0; } B. private int blipvert(int x) { return 0; } C. private int blipvert(long x) { return 0; } D. protected long blipvert(int x) { return 0; } E. protected int blipvert(long x) { return 0; } F. protected long blipvert(long x) { return 0; } G. protected long blipvert(int x, int y) { return 0; }
16.
Explain Given: 5. class Atom { 6. Atom() { System.out.print("atom "); } 7. } 8. class Rock extends Atom { 9. Rock(String type) { System.out.print(type); } 10. } 11. public class Mountain extends Rock { 12. Mountain() { 13. super("granite "); 14. new Rock("granite "); 15. } 16. public static void main(String[] a) { new Mountain(); } 17. } What is the result? A. Compilation fails. B. atom granite C. granite granite D. atom granite granite E. An exception is thrown at runtime. F. atom granite atom granite
17.
Explain Given: 10. class Nav{ 11. public enum Direction { NORTH, SOUTH, EAST, WEST } 12. } 13. public class Sprite{ 14. // insert code here 15. } Which code, inserted at line 14, allows the Sprite class to compile? A. Direction d = NORTH; B. Nav.Direction d = NORTH; C. Direction d = Direction.NORTH; D. Nav.Direction d = Nav.Direction.NORTH;
18.
Explain IF you are remotely logged on to a Solaris machine, What command would you execute?
19.
Explain Given:
21. class Money {
22. private String country = "Canada";
23. public String getC() { return country; }
24. }
25. class Yen extends Money {
26. public String getC() { return super.country; }
27. }
28. public class Euro extends Money {
29. public String getC(int x) { return super.getC(); }
30. public static void main(String[] args) {
31. System.out.print(new Yen().getC() + " " + new Euro().getC());
32. }
33. }
What is the result?
A. Canada
B. null Canada
C. Canada null
D. Canada Canada
E. Compilation fails due to an error on line 26.
F. Compilation fails due to an error on line 29.
20.
Explain Given:
11. class PingPong2 {
12. synchronized void hit(long n) {
13. for(int i = 1; i < 3; i++)
14. System.out.print(n + "-" + i + " ");
15. }
16. }
17. public class Tester implements Runnable {
18. static PingPong2 pp2 = new PingPong2();
19. public static void main(String[] args) {
20. new Thread(new Tester()).start();
21. new Thread(new Tester()).start();
22. }
23. public void run() { pp2.hit(Thread.currentThread().getId()); }
24. }
Which statement is true?
A. The output could be 5-1 6-1 6-2 5-2
B. The output could be 6-1 6-2 5-1 5-2
C. The output could be 6-1 5-2 6-2 5-1
D. The output could be 6-1 6-2 5-1 7-1