P Teng

Hi, can some one pl confirm how is the marking done for questions with more than one correct answer (checkbox type) in OCJA. If one chooses two options out of which only one is correct then does the candidate score any marks (50% in this case for the question).

Thank you all.

Excellent
That explains it.
Perhaps thats why it does not like b = b * 2 but likes the former b *= 2

Thanks Matthew.

Hello,

Thank you very much for your reply.
but why does this not apply to b *= 1 as that too is a mathematical action.

Hi
lass ByteTest { public static void main(String[] args) { byte b = 100; b *= 2; // line 1 b = b + 1; // line 2 } }

why does line 1 not give the same error as line 2 (possible loss of precision). Why is the 2 in line 1 not treated as an integer.

I had already posted my queries to [email protected]. I have done that again today.

Yes, I too agree with the observation regarding there support. I too posted a question to them about 2-3 weeks back and have still to hear from any one (at least I did not get the mail box full !). I have had doubts about a couple of question and am awaiting a reply from them.

Thanks Rob, that helps.

Meanwhile I have also found that the PriorityQueue is NOT thread safe. One can use PriorityBlockingQueue instead.

The earlier example if reworked as below works

import java.util.*; import java.util.concurrent.*; // needed for PriorityQueueBlocking class class PriorityEx1 { static class PQSort implements Comparator<Integer> { public int compare (Integer first, Integer second) { return (second - first); } } public static void main (String[] args) { int[] ia = {2,8,9,5,7,1,4,3,6}; // demonstrate natural priority // PriorityQueue<Integer> pq1 = new PriorityQueue<Integer>(); // causes run time error PriorityBlockingQueue<Integer> pq1 = new PriorityBlockingQueue<Integer>(); for (int x: ia) pq1.offer(x); for (int x: pq1) System.out.print(pq1.poll() + " "); System.out.println(" "); } }

Hi,
When I run the below code I get a run time exception. Could you please see what could be wrong. Is this not correct use of poll() ? .

There is a similar example in Book for exam 310-065, generics and collections, Chapter 7

import java.util.*; class PriorityEx1 { static class PQSort implements Comparator<Integer> { public int compare (Integer first, Integer second) { return (second - first); } } public static void main (String[] args) { int[] ia = {2,8,9,5,7,1,4,3,6}; // demonstrate natural priority PriorityQueue<Integer> pq1 = new PriorityQueue<Integer>(); for (int x: ia) pq1.offer(x); for (int x: pq1) System.out.print(pq1.poll() + " "); System.out.println(" "); // demonstrates user defined priority } }

error that I get is

1 Exception in thread "main" java.util.ConcurrentModificationException at java.util.PriorityQueue$Itr.next(Unknown Source) at PriorityEx1.main(PriorityEx1.java:25)

Can some one please explain the output caused by line 1

class FormatEx1 { public static void main(String[] args) { int i1 = 12345; int i2 = -12345; float f1 = -98.56f; String s1 = "hello world"; System.out.printf("%1$7d",i1); System.out.println(); System.out.printf("%1$(7f",f1); // line 1 System.out.println(); System.out.printf("%1$+2.5f",f1); System.out.println(); System.out.printf("%1$+(5d",i1); System.out.println(); System.out.printf("%1$+-5d",i2); System.out.println(); System.out.printf("%1$,-5d",i2); } }

output is below. What causes 559998 to appear after the . instead of just 56
12345 (98.559998) -98.56000 +12345 -12345 -12,345

Hi , a quick one please

The following code does not compile, complaining that it cannot find symbol : variable y.
Does this mean that variables in static or not static code blocks are limited in scope only to that block only if they have been declared there ?

class Temp { static { int y=99; System.out.println("static block" + y); } Temp() { System.out.println(y); // fails here } public static void main(String[] args) { Temp temp = new Temp(); } }

the answer is A because when aa=null eecutes, there is no outside world referene that can help reach to objets of class A or B. Hence all objects are eligible for GC

Thanks guys. This helps.

String are supposed to be immutable, how ever it seems from below that even Integer could be immutable as well, can some one please explain that when we assign an Integer reference to another the same String immutable behaviour happens. Even though Integer j is assigned a reference to Integer i, and when I change i, j remains unaffected. Can some one please explain

class Assignments2 { int var1; public static void main(String[] args) { // --- Assignments2 assignments2 = new Assignments2(); Assignments2 assignments = assignments2; assignments2.var1 = 77; System.out.println(assignments.var1); assignments.var1 = 79; System.out.println(assignments2.var1); System.out.println("---"); String x = "Java"; String y = x; System.out.println("y= "+y); x += " Bean"; System.out.println("y= "+y); // --- System.out.println("---"); Integer i = 32; // or just Integer i = 32; Integer j = i; System.out.println("j= "+j); i += 10; System.out.println("j= "+j); } }

output is
77 79 --- y= Java y= Java --- j= 32 j= 32

Thanks guys, it must be one of the PATH settings or the version. The same code works at home. Thanks Ritchi ! Hope to hear/tell/learn lot more in the forum in the future.