Sun Certified Java Developer Question: Download Sun Certification PDF

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.

Answer:

B:An exception is thrown at runtime.

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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

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;