Duvida...Thread...OO.....<?>

Section 4: Concurrency > Objective 4.2 > Question 37 
Given: 

 5. class Order2 implements Runnable {
 6.   public void run() { 
 7.     for(int x = 0; x < 4; x++) {
 8.       try { Thread.sleep(100); } catch (Exception e) { }
 9.       System.out.print("r");
10.   } }
11.   public static void main(String [] args) {
12.     Thread t = new Thread(new Order2());
13.     t.start();
14.     for(int x = 0; x < 4; x++) {
15.       // insert code here
16.       System.out.print("m");    
17. } } }

Which, inserted at line 15, is most likely to produce the output rmrmrmrm?

A Thread.sleep(1);
B Thread.sleep(100);
C Thread.sleep(1000);
D try { Thread.sleep(1); } catch (Exception e) { }
E try { Thread.sleep(100); } catch (Exception e) { }
F try { Thread.sleep(1000); } catch (Exception e) { }

Section 4: Concurrency > Objective 4.3 > Question 39 
Given: 

 5. class NoGo implements Runnable {
 6.   private static int i;
 7.   public synchronized void run() { 
 8.     if (i%10 != 0) { i++; }
 9.     for(int x=0; x<10; x++, i++) 
10.       { if (x == 4) Thread.yield(); }
11.   }
12.   public static void main(String [] args) {
13.     NoGo n = new NoGo();
14.     for(int x=0; x<101; x++) { 
15.       new Thread(n).start(); 
16.       System.out.print(i + " ");
17. } } }

Which is true?

A The output can never contain the value 10. 
B The output can never contain the value 30. 
C The output can never contain the value 297. 
D The output can never contain the value 820. 
E Making the run method un-synchronized will not change the possible output.

Section 5: OO Concepts > Objective 5.1 > Question 41 
Given: 

 1. class TestFoo {
 2.   int x;
 3.   String y;
 4.   int getX() { return x; }
 5.   String getY() { return y; }
 6.   void setX(int x) {
 7.     int z = 7;
 8.     this.x = x;
 9.   }
10. }

How many modifiers must you add to encapsulate this class?

A 2 
B 3 
C 4 
D 5

Section 5: OO Concepts > Objective 5.1 > Question 42 
Given: 

21. class Wheels { 
22.   private Bike bike;
23.   void setBike(Bike b) { bike = b; }
24. }
25.
26. class Bike {
27.   private Wheels [] wheels = new Wheels[5];
28.   void setWheels(Wheels [] w) {
29.      if( w.length == 2)
30.        wheels = w;
31.   }
32. }

Which is true?

A Compilation fails. 
B These classes are NOT coupled. 
C These classes are loosely coupled. 
D These classes are tightly coupled. 
E These classes are abstractly coupled.

Given: 

1. class Book {
2.   private final void read() { System.out.print("book "); }
3. }
4. class Page extends Book {
5.   public static void main(String [] args) {
6.     // insert code here
7.   }
8.   private final void read() { System.out.print("page "); }
9. }

And these three code fragments (x, y, z): 
x. // just a comment
y. new Page().read();
z. new Book().read();
How many, inserted independently at line 6, allow the code to compile and run without exception?


A 0 B 1 C 2 D 3

class Stuff implements Comparable {
	    int x; 
	    Stuff(int x) { 
	    	this.x = x;
	    }
	    public int compareTo(Object o) { return 0; }
	  }

public class Ex58 {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		TreeSet<Stuff> ts = new TreeSet<Stuff>();
		ts.add(new Stuff(1));
		ts.add(new Stuff(2));
		ts.add(new Stuff(3));
		System.out.println(ts.size());
	}

}

public static void main(String[] args) {
		// TODO Auto-generated method stub
		     HashMap h = new HashMap();
		      h.put("a","aa"); h.put("b","bb"); h.put("c","cc");
		      Set ks = h.keySet();
		      Object [] ka1 = ks.toArray();
		      ks = new TreeSet(ks);
		      Object [] ka2 = ks.toArray();
		     System.out.println(Arrays.equals(ka1, ka2));
		     
		     for(Object s:ka1){
		    	 System.out.println("ka1"+(String)s);
		     }
		     //System.out.println("ka1="+ka1.toString());
		     //System.out.println("ka2="+ka2.hashCode());
		     for(Object s:ka2){
		    	 System.out.println("ka2="+(String)s);
		     }
	}

}
resultado:
false
ka1a
ka1c
ka1b
ka2a
ka2b
ka2c