Difference speeds between Java�s data structures?

Hello,
I would appreciate to know, if there are any real efficiency differences between the data structures?
One of my programs using s Vector to store 50 thousand small class objects.
Adding to the vector seems quite slow, would anyone say the ArrayList/LinkedList is quicker. And the ArrayList/LinkedList are also quicker when looping through the objects again?
Cheers

ArrayList is basically the same as a Vector without the synchronization (and IIRC some slightly different default values). So if you don't need synchronization using an ArrayList is a sure, safe way to increase performance. Wether the gain is measurable depends on your problem. The question wether to use ArrayList or LinkedList depends mostly on how you access the values (do you need random access? do you just loop over them? do you need to insert values at the beginning or the middle?)

Similar Messages

Difference in two java.SQL.Date in Days

Collegues,
I have two java.sql.Dates. One sendDate and other is recieveDate. Could you please tell me how can I calculate the diffenence in these two dates in Days.
Thank you

HI DOCSOFT
here is the code
public int DayDiff(String start, String end)
try
SimpleDateFormat dateFormat = new SimpleDateFormat("dd/MM/yyyy");
Date startDate = dateFormat.parse(start);
Date endDate = dateFormat.parse(end);
GregorianCalendar calStart = new GregorianCalendar();
calStart.setTime(startDate);
GregorianCalendar calEnd = new GregorianCalendar();
calEnd.setTime(endDate);
if (calStart.get(Calendar.YEAR) == calEnd.get(Calendar.YEAR))
return calEnd.get(Calendar.DAY_OF_YEAR) - calStart.get(Calendar.DAY_OF_YEAR);
else if ((calEnd.get(Calendar.YEAR) - calStart.get(Calendar.YEAR)) == 1)
int daysEndYear = calEnd.get(Calendar.DAY_OF_YEAR);
int daysStartYear = calStart.getActualMaximum(Calendar.DAY_OF_YEAR) - calStart.get(Calendar.DAY_OF_YEAR);
return daysEndYear + daysStartYear;
else
int startYear = calStart.get(Calendar.YEAR);
int endYear = calEnd.get(Calendar.YEAR);
GregorianCalendar cal = new GregorianCalendar();
int days = 0;
for (int i = startYear + 1; i < endYear; i++)
cal.set(Calendar.YEAR, i);
days += cal.getActualMaximum(Calendar.DAY_OF_YEAR);
days += calEnd.get(Calendar.DAY_OF_YEAR);
days += (calStart.getActualMaximum(Calendar.DAY_OF_YEAR) - calStart.get(Calendar.DAY_OF_YEAR));
return days;
catch (ParseException e)
return -1;
sorry about the formatting
hope this works
Regards
Satinderjit

Conversions between java.util.Date, java.util.Timestamp and java.sql dates

I am coding a hoilday booking system using JSP to interact with a SQL Server database. On my JSP form which retrieves the information I have a little javascript pop-up date selector which appears to be returning a Timestamp value although the string value is visable in the entry field. Can I pass this to a javabean as a Timestamp, so far I have only passed strings? Also I then have to enter it in the database and so will need to convert it to an sql date type but I dont know which one is best. Previous to using the Timestamp returning calendar I was just entering text and parsing it to a util.Date in the bean and then converting that to an sql.Date for entry in the database. That worked fine but I want to use the pop-up any ideas? Also my bean won't compile if I declare java.util.Timestamp t;(cannot resolve symbol Timestamp !) even though I have imported util.

First of all, java.util.Timestamp does not exist. You probably need java.sql.Timestamp.
java.sql.Date and java.sql.Timestamp inherit from java.util.Date. So converting from java.sql.Date or java.sql.Timestamp to java.util.Date is easy, you don't have to do anything.
To convert a java.util.Date to a java.sql.Timestamp, do something like this:
import java.sql.Timestamp;
import java.util.Date;
Date date = new Date();
Timestamp ts = new Timestamp(date.getTime());Jesper

Relationship between Dynamic Memory Heap and Heap Data Structure

This question is not strictly related to Java, but rather to programming in general, and I tend to get better answers from this community than any where else.
Somehow, my school and industry experience have somehow not given me the opportunity to explore and understand heaps (the data structure), so I'm investigating them now, and in particular, I've been looking at applications. I know they can be used for priority queues, heap sorts, and shortest path searches. However, I would have thought that, obviously, there must be some sort of relationship between the heap data structure, and the dynamic memory heap. Otherwise, I can think of no good reason why the dynamic memory heap would be named "heap". Surprisingly, after searching the web for 90 minutes or so, I've seen vague references, but nothing conclusive (trouble seems to be that it's hard to get Google to understand that I'm using the word "heap" in two different contexts, and similarly, it would not likely understand that web authors would use the word in two different contexts).
The Java Virtual Machine Spec is silent on the subject, as "The Java virtual machine assumes no particular type of automatic storage management system, and the storage management technique may be chosen according to the implementor's system requirements."
I've seen things like:
[of dynamic memory] "All the blocks of a particular size are kept in a sorted linked list or tree (I extrapolate that sorted tree could imply heap)"
[of dynamic memory] "The free and reserved areas of memory are maintained in a data structure similar to binary trees called a heap"
[of dynamic memory] "This is not related to the heap data structure"
[of dynamic memory] "Not to be confused with the data structure known as a "heap"
[of data structure] "Not to be confused with the dynamic memory pool, often known as TheHeap"
At this point, I've come to surmise that some (but not all) memory management algorithms use heaps to track which (pages? blocks? bytes?) of memory are used, and which are not. However, the point of a heap is to store data so that the max (or min) key is at the root of the heap. But we might want to allocate memory of different sizes at different times, so it wouldn't make sense to key on the amount of available memory in a particular region of the free store.
I must assume then that there would be a different heap maintained for each size of memory block that can be allocated, and the key must have something to do with the attractiveness of the particular memory block in the heap (perhaps the lowest address, resulting, hopefully, in growing the free store space less often, leaving more space for the stack to grow, or perhaps keyed based on the fragmentation, to hopefully result in less fragmentation, and therefore more efficient use of the memory space, or perhaps based on page boundaries, keeping as much data in the same page as possible, etc).
So at this point, I have a few questions I've been unable to resolve completely:
1. Am I correct that the heap was so named because (perhaps at one point in time), a heap is/was commonly used to track the available memory in the free store?
2. If so, would it be correct that there would be a heap per standard block size?
3. Also, at what level of granularity would a heap typically be used (memory page, memory blocks, individual words (4-bytes))?
4. What would be the most likely property one would use as a key. That is, what makes the root item on the heap ideal?
5. Would a industrial strength system like the jvm use a (perhaps modified or tuned) heap for this sort of task, or would this typically be too naive for an real world solution today?
Any insight would be awesome!
Thanks,
A.

jschell wrote:
I think you are not only mixing terms but domains.
For starters the OS allocs memory. Applications, regardless of language, request memory from the OS and use it in various ways.
There are many variations of the term "heap" like the following.
[http://en.wikipedia.org/wiki/Heap_(data_structure)]
[http://en.wikipedia.org/wiki/Dynamic_memory_allocation]
A java VM will request memory from the OS (from a 'heap') and use it in its application 'heap' (C/C++) and then create the Java 'heap'. There can be variations of that along the way that can and likely will include variations of how each heap is used, potentially code that creates its own heap, and potentially other allocators which use something which is not a heap.This last part, I find a bit confusing. By "use something which is not a heap", do you mean the heap data structure, or the dynamic memory pool meaning of heap? If the former, then you would be implying that it would be common for a heap data structure to be used to manage the heap dynamic memory pool. If the latter, what would this "something which is not a heap" be? The best definition of "heap" I've found simply states that it is a pool of memory that can be dynamically allocated. If there is some other way of allocating dynamic memory, then it would suggest that the previous definition of "heap" is incomplete.
>
So to terms.
1. Am I correct that the heap was so named because (perhaps at one point in time), a heap is/was commonly used to track the available memory in the free store?Which 'heap'? The VM one? It is probably named that because the implementors of the Sun VM were familar with how C++ and Smalltalk allocated memory.Okay, but that begs the question, was the heap in C++ and/or Smalltalk so named for the above queried reason?
>
2. If so, would it be correct that there would be a heap per standard block size?Not sure what you are referring to but probably a detail of the implementation. And since there are different levels the question doesn't mean much.
However OS allocations are always by block if that helps. After that it requires making the question much, much more specific.
3. Also, at what level of granularity would a heap typically be used (memory page, memory blocks, individual words (4-bytes))?Again not specific enough. A typical standard implementation of heap could not be at the word level. And it is unlikely, but not impossible, that variations would support word size allocations.
The VM heap might use word boundaries (but not size), where the application heap certainly does (word boundary.)My understanding of it is that the application would request blocks from the OS, and then something like malloc would manage the memory within the allocated blocks. malloc (or whatever equivalent Java uses) would have to keep track of the memory it has allocated somehow, and I would think it would have to do this at the word level, since it's most commonly going to allocate memory at the word level to be references to other objects, etc.
So I guess my question here would really be, if the dynamic memory heap is so named because there has been a memory management strategy that relied upon a heap data structure (which I've found no proof, but have found some suggestive literature), then would that probably have applied at the OS Page Fault level, tracking allocated blocks, or would that have applied at the malloc level, allocating individual words as necessary?
>
4. What would be the most likely property one would use as a key. That is, what makes the root item on the heap ideal?"Key" is not a term that will apply in this discussion.
You appear to be referring to strategies for effective allocation of memory such as allocations from different regions by size comparison.
It is possible that all levels might use such an allocator. General purpose applications do not sort allocations though (as per your one reference that mentions 'key'.) Sorry, I got the term "key" from an article I read regarding heaps, that indicates that a "key" is used to sort the elements, which I guess would be a more generalized way to make a heap than assuming a natural ordering on the elements in the heap. I'm not sure if the terminology is standard.
>
5. Would a industrial strength system like the jvm use a (perhaps modified or tuned) heap for this sort of task, or would this typically be too naive for an real world solution today?Again too indefinite. The Sun VM uses a rather complicated allocator, the model for which originated after years of proceeding research certainly in Smalltalk and in Lisp as well, both commercially and academically.
I am sure the default is rules driven either explicitly or implicitly as well. So it is self tuning.
There are command line options that allow you to change how it works as well.I guess perhaps I could attempt to clarify my initial question a bit.
There is a 1:1 correspondence between the runtime stack, and a stack data structure. That is, when you call a function, it pushes a stack frame onto the runtime stack. When you return from a function, it pops a stack frame from the runtime stack. This is almost certainly the reasons the runtime stack is named as it is.
The question is, is there or has there ever been a 1:1 correspondence between some aspect of the dynamic memory heap or how it is managed, and a heap data structure? If so, it would explain the name, but I'm a bit puzzled as to how a heap data structure would be of assistance in creating or managing the dynamic memory heap. If not, on the other hand, then does anybody know where the name "heap" came from, as it applies to the dynamic memory pool?
A.

Trees Data Structures in Java

Hi all !
Currently I�m developing a Java software that requires a Tree data structure. Searching through Java API I�ve found classes like TreeMap and TreeSet, but although these classes seens to use tree structure behind what they really provide are linear data structure, not a tree data structure. My question is if there is a public and free Java tree data structure that permits to do activities such as:
- Search for a particular node (efficiently)
- Insert children to any node
- Maintain one Object in each node
Simple like this ! It must have something like this in Java, but I just can�t find it and I�m just too lazy to implement it :) ! Anyone can help me ?
Thanks in advance !

Mel,
I�ve seen javax.swing.tree.TreeModel and its seens more like an implementation of Control in swing MVC (Model Vision Control) swing paradigm for JTree. It has listeners generated for manipulation events for example. It uses javax.swing.tree.DefaultMutableTreeNode for its nodes, and maybe I could use this class for the nodes of my tree since it has many useful operations. However still I miss a node searching operation that this class doesn�t have.
Yes my problem is a simple Tree, but it is simple now and it might become much more complex, demanding more operations on the tree and specially efficient searching algorithms. Thats why I�m looking for a complete solution and I prefer something that is already done and well tested :) !
Thanks for your tip !

Help converting between Java Dates and SQL Dates

Hey all,
I'm working on a JSP to allow a user to enter information about news articles into a mySQL database. I'm using text fields for most of the data, and most of it is transferred correctly when the user hits "Submit." However, I am having a problem with the date field of the mySQL database. Basically I'm trying to retrieve the current date from the JSP page, and then insert this into the date field of the appropriate table when the user hits submit. The problem is that I can't typecast a java.util.Date or even a java.util.Calendar to a java.sql.Date object. I've tried lots of approaches, including creating a new instance of java.util.Calendar, getting all its fields and concatenating them onto the date variable, but this doesn't work.
Anyone know how I could easily convert between java.util.Date or java.util.Calendar and java.sql.Date?
Thanks!

Thanks for the help!
I can correctly display the current date on the page in java.sql.Date format now, but it's still not being inserted into the database correctly. The specific code is as follows:
java.util.Date dt = new java.util.Date();
java.sql.Date sqlDate = new java.sql.Date(dt.getTime());
(As you wrote)
Then (after connecting to the database etc.):
PreparedStatement pstmt = con.prepareStatement("INSERT INTO NEWS(NEWSDATE,DAYOFWEEK,AUTHOR,HEADLINE,CLIP,PUBLICATION,LINK,NEWSLOCATION,DATECREATED,DATEMODIFIED,CATEGORY,KEYWORDS,PHOTOURL,PHOTOGRAPHER,AUDIOURL) VALUES (?,?,?,?,?,?,?,?,?,?,?,?,?,?,?)");
pstmt.clearParameters();
pstmt.setString(1,date);
pstmt.setString(2,dayofweek);
pstmt.setString(3,author);
pstmt.setString(4,headline);
pstmt.setString(5,clip);
pstmt.setString(6,publication);
pstmt.setString(7,link);
pstmt.setString(8,newslocation);
pstmt.setDate(9,sqlDate);
pstmt.setString(10,datemodified);
pstmt.setString(11,category);
pstmt.setString(12,keywords);
pstmt.setString(13,photoURL);
pstmt.setString(14,photographer);
pstmt.setString(15,audioURL);
int i = pstmt.executeUpdate();
pstmt.close();
All the other fields are retrieved with request.getParameter from text fields. Any idea why the DATECREATED field is being updated to all 0's but the others work fine?
Thanks again.

(Again) java.util.Date vs java.sql.Date

Hi there,
(Again) Im trying to understand the EXACT difference between
java.util.Date vs java.sql.Date.
Googling, I can see that this is a very "popular" subject, but I still
cannot figure out it exactly.
Many writers claim that java.sql.Date only stores the DATE part (yyyy-
mm-dd) but not the TIME part (hh:MM:ss) of a Date/Time value, but that
I can easily disprove:
java.util.Date ud = new java.util.Date(); java.sql.Date sd = new java.sql.Date(ud.getTime()); System.out.println(DateFormatUtils. format(ud, "yyyy-MM-dd HH:mm:ss.SSS")); System.out.println(DateFormatUtils. format(sd, "yyyy-MM-dd HH:mm:ss.SSS"));
Output:
2009-09-18 15:17:36.635 2009-09-18 15:17:36.635
So, apparently, java.sql.Date and java.util.Date have THE SAME
precision (at least down to the millisecs...).
And the official API documentation, really looks more confusing than
helpful to me::
*"java.sql.Date:*
*A thin wrapper around a millisecond value that allows JDBC to identify*
*this as an SQL DATE value. A milliseconds value represents the*
*number of milliseconds that have passed since January 1, 1970*
*00:00:00.000 GMT.*
*To conform with the definition of SQL DATE, the millisecond values*
*wrapped by a java.sql.Date instance must be 'normalized' by setting*
*the hours, minutes, seconds, and milliseconds to zero in the*
*particular time zone with which the instance is associated. "*
Exactly what means "an SQL DATE value" ? How EXACTLY does it differ
from a java.util.Date value?
Most importantly: WHY does JDBC need to distinguish between them?
And, here again: *"a java.sql.Date instance must be 'normalized' by*
*setting the hours, minutes, seconds, and milliseconds to zero in the*
*particular time zone..."*
What does that mean exactly? Apparently, the constructor doesnt
enforce this restriction, per the example above. So what's the REAL
point with this type, java.sql.Date?
Very greatful, if you can help me clarify this, once and for all.
TIA,

And the official API documentation, really looks more confusing than helpful to me:The problem is that you need to understand SQL as well as Java for this to make sense. It's not the Java API's job to tell you how your SQL database works - there's a myriad of subtle differences even when the DB is compliant with the SQL spec.
Most compliant databases support DATE, TIME, and TIMESTAMP values. DATE represents only a date. TIME represents only a time. TIMESTAMP represents both. There are further complicating factors, but that's roughly how it stands.
In Java the normal type for representing time is (or was when the API was created) the java.util.Date but this is a close approximation only to the TIMESTAMP value. In order to bring the two together the java.sql.Date, java.sql.Time and java.sql.Timestamp classes were created. Making them derive from java.util.Date was probably not a good idea.
java.util.Date suffers from a number of deficiencies. java.util.Calendar was supposed to address them but didn't really succeed. The JodaTime library is rather better, but it's all a lot more complicated than you might expect - partly because time management really is a much harder problem than it appears at first glance - there are timezones, leap years, leap seconds, the difference between astronomical and atomic time, and so on and so forth.

Does anyone know what the difference is in the various dates in LR?

Does anyone know what the differences are between the following:
Date Time Original
Date Time Digitalized
Date Time
I understand that Date Time Original is the capture time and that Date Time is capture time except when the image is a copy of another image that was created using Edit In... So, what is Date Time Digitalized?
Thank you.
Brian

The SOL is 4 years in TX and the DOFD is usually the first time it hits 30 days late and is not brought back current

Data conversion for communication between Java and C/C++ program

The real problem, i guess, is about data type conversion between Java and C programs. For instance, and int is supposed to be 4 bytes in Java, and also in C/C++. But, as far as I know, the size of and int in C depends on the processors architecture, so if it were a 64 bit arch., size of and int, double, etc. in C, would change. The real scenario would be a communication between a 32 bit machine (Java) and a 64 bit machine (C/C++).
First of all, is this assumption correct?
If so,
how is it possible to deal with this problem in Java?
Is there any way to know 'type length' automatically? or
would it be necessary to modify the Java program to work with a C program in 32-bit or 64-bit arch?
thx in advance

cotton.m wrote:
Yes you should develop the C part of the protocol first and then build from there.
See http://forum.java.sun.com/thread.jspa?threadID=5243547 for a previous discussion of this topic.
I understand what you mean, also the topic you referenced. I will explain the situation a bit more. The protocol is already defined: (16 bits message size, 16 message id, 32 bit time, etc.); it is also defined in C (structures and so on). So it would be easy to write my Java code using the specified protocol in bytes, and C types wouldn't be necessary to be considered. But, let's say that the C code can't be modified, and I thought (and don't know yet if its correct), that size of C types CAN changed depending on architecture. So if size changes for C types (code is specified in short, int, etc, and not in bit format), it all would be a mess, if I don't implement something in my Java code.
cotton.m wrote:
I don't believe that 32 or 64 bit enters the equation here at all.Maybe 32 o 64 doesn't mind, but sparc or PC could take a point here. Communication would be between a sun solaris sparc and windows x86 PC. But if type size in C/C++ does not change, I wouldn't really have any problem then...
The situation is not ideal, I know, but is what I have; and I think I could have problems if I run the C program in other machines; so I would have to try to solve it whithin my Java Program.
I hope it is clear now what I need.
thx
Edited by: MGasa on Jan 16, 2008 1:51 AM

Bit shifting tricks and speeding up data structure

I'm pretty new to working directly with bits, but it is a lot of fun. I'm converting a javascript data structure to Flash.
So I'm thinking that Math.floor(uint/32) is the same as uint >> 5, right?
And that uint % 32 is the same as uint & 31 ? Evidently this works for modulos that are powers of 2, what a cool trick.
Using both of those cut the time needed for storing and retrieving data about in half.
But it is still takes about three times longer that just using the native Object. This is in reference to my previous post http://forums.adobe.com/message/5001353#5001353 but that didn't get very far.
So if anybody has any suggestions on how else to speed this up it would be very helpful:
package {
          public class BloomFilter {
                    private var _m:uint;
                    private var _k:int;
                    private var _locations:Vector.<uint>;
                    public var _buckets:Vector.<uint>;
                    public function BloomFilter(m:uint,k:int) {
                              _m=m;
                              _k=k;
                              _locations=new Vector.<uint> ;
                              _buckets=new Vector.<uint> ;
                              var n:uint=Math.ceil(m/32);
                              var i:int=-1;
                              while (++i<n) {
                                        _buckets[i]=0;
                    private function hash(v:String) {
                              var i:int=-1;
                              var X:uint;
                              var a,b:uint;
                              a=fnv_1a(v);
                              b=fnv_1a_b(a);
                              X=a%_m;
                              while (++i<_k) {
                                        _locations[i]=X<0? (X+_m) : X;
                                        X=(X+b)%_m;
                    public function add(v:String) {
                              hash(v);
                              var i:int=-1;
                              while (++i<_k) {
                                        _buckets[_locations[i]>>5]|=1<<(_locations[i]&31);
                    public function test(v:String):Boolean {
                              hash(v);
                              var i:int=-1;
                              var b:uint;
                              while (++i<_k) {
                                        b=_locations[i];
                                         if ((_buckets[b>>5] & (1 << (b&31))) === 0) {
                                                  return false;
                              return true;
                    // Fowler-Noll-Vo hash
                    private function fnv_1a(v:String):uint {
                              var n:int=v.length;
                              var a:uint=2166136261;
                              var c,d:uint;
                              var i:int=-1;
                              while (++i<n) {
                                        c=v.charCodeAt(i);
                                        if (d=c&0xff000000) {
                                                  a^=d>>24;
                                                  a+=(a<<1) + (a<<4) + (a<<7) + (a<<8)+ (a<<24);
                                        if (d=c&0xff0000) {
                                                  a^=d>>16;
                                                  a+=(a<<1) + (a<<4) + (a<<7) + (a<<8)+ (a<<24);
                                        if (d=c&0xff00) {
                                                  a^=d>>8;
                                                  a+=(a<<1) + (a<<4) + (a<<7) + (a<<8)+ (a<<24);
                                        a^=c&0xff;
                                        a+=(a<<1) + (a<<4) + (a<<7) + (a<<8)+ (a<<24);
                              a+=a<<13;
                              a^=a>>7;
                              a+=a<<3;
                              a^=a>>17;
                              a+=a<<5;
                              return a&0xffffffff;
                    // One additional iteration of FNV
                    private function fnv_1a_b(a:uint):uint {
                              a+=(a<<1) + (a<<4) + (a<<7) + (a<<8)+ (a<<24);
                              a+=a<<13;
                              a^=a>>7;
                              a+=a<<3;
                              a^=a>>17;
                              a+=a<<5;
                              return a&0xffffffff;

the math shortcuts, as mentioned above, have a greater benefit. (and thanks. yes, that's from a book i wrote,
Flash Game Development: In A Social, Mobile and 3D World
Math Class Shortcuts
These methods actually do provide a benefit and that benefit can be significant even without needing millions of operations to realize. They are listed in alphabetical order starting with Math.abs. (See support files/Chapter 07/math_class/Math.abs_v_conditional.fla, support files/Chapter 07/math_class/Math.floor_v_int.fla etc.)
Math.abs
Using
x = (y<0) ? -y: y;
instead of
x = Math.abs(y)
is about twice as fast. Unless you are using millions of Math.abs operations, you should not expect a noticeable benefit from using the inline code. In addition, the inline code is cumbersome.
var xx:int;
var n:int = 10000000;
var n2:int = n/2;
var i:int;
var startTime:int = getTimer();
//// Math.abs duration: 1016
for(i=0;i<n;i++){
       xx = Math.abs(n2-i);
trace("Math.abs duration:",getTimer()-startTime);
// conditional duration: 445
startTime = getTimer();
for(i=0;i<n;i++){
        xx = (n2-i<0) ? i-n2 : n2-i;
trace("conditional duration:",getTimer()-startTime);
Math.ceil and Math.floor
Using
x = int(y);
Instead of
x = Math.floor(y); // y>=0
x = Math.ceil(y); // y<=0
Is about twice as fast. Unless you are using millions of Math.floor operations (with non-negative numbers), you should not expect a noticeable benefit.
var i:int;
var n:int = 10000000;
var xx:int;
var startTime:int = getTimer();
// Math.floor duration: 1105
for(i=0;i<n;i++){
       xx = Math.floor(i/n);
trace("Math.floor duration:",getTimer()-startTime);
// int duration: 479
startTime = getTimer();
for(i=0;i<n;i++){
       xx = int(i/n);
trace("int duration:",getTimer()-startTime);
Math.max
Using
x = (i>j) ? i : j;
instead of
x = Math.max(i,j);
is about twice as fast.
This shortcut is also cumbersome but has the greatest benefit (along with Math.min) of all those listed in this section. Notice the difference in time required to execute the code blocks and how few iterations are needed to demonstrate that difference.
var xx:int;
var n:int = 1000;
var i:int;
var j:int;
var startTime:int;
// Math.max duration: 109
startTime = getTimer();
for(i=n-1;i>=0;i--){
       for(j=n-1;j>-0;j--){
              xx = Math.max(i,j);
trace("Math.max duration:",getTimer()-startTime);
// conditional duration 43
startTime = getTimer();
for(i=n-1;i>=0;i--){
       for(j=n-1;j>-0;j--){
               xx = (i>j) ? i : j;
trace("conditional duration",getTimer()-startTime);
Math.min
Using
x = (i<j) ? i : j;
instead of
x = Math.min(i,j);
is about twice as fast.
This shortcut is also cumbersome but has the greatest benefit (along with Math.max) of all those listed in this section. Notice the difference in time required to execute the code blocks and how few iterations are needed to demonstrate that difference.
var xx:int;
var n:int = 1000;
var i:int;
var j:int;
var startTime:int;
// Duration Math.min 121
startTime = getTimer();
for(i=0;i<n;i++){
       for(j=0;j<n;j++){
              xx = Math.min(i,j);
trace("Duration Math.min",getTimer()-startTime);
// Duration conditional 43
startTime = getTimer();
for(i=0;i<n;i++){
       for(j=0;j<n;j++){
               xx = (i<j) ? i : j;
trace("Duration conditional",getTimer()-startTime);
Math.pow
It is two to three times faster to explicitly multiply a number variable compared to using Math.pow. That benefit even extends a little beyond integer exponents because Math.sqrt(i) is about twice as fast as Math.pow(i,.5).
var i:int;
var n:int = 10000000;
var xx:int;
var startTime:int;
// exp .5: 2020, exp 2: 1533, exp 3: 1617, exp 4: 1427, exp 5: 1381, exp 10: 1391
startTime = getTimer();
for(i=0;i<n;i++){
       xx = Math.pow(i,.5);
trace("Duration Math.pow",getTimer()-startTime);
// exp .5: 1064, exp 2: 427, exp 3: 778, exp 4: 557, exp 5: 501, exp 10: 586
startTime = getTimer();
for(i=0;i<n;i++){
       xx = Math.sqrt(i);
trace("Duration iteration",getTimer()-startTime);

Difference between using new Date() and new Date(System.currentTimeMillis()

Hi All,
I have seen many open source api's where they are updating dates with the following code
new Date(System.currentTimeMillis())
when i print the new Date() it prints the same
what is the difference between using new Date() and new Date(System.currentTimeMillis()) ??
Thanks,
J.Kathir

when i print the new Date() it prints the same
It does because of backward compatability. This constructor exists in version 1.3.1 but not in newer versions.Really ? Please point me to where you read that.
API doc 1.5 : new Date() (still there, not even deprecated)
A quick look at the code for this constructor:    /**
     * Allocates a <code>Date</code> object and initializes it so that
     * it represents the time at which it was allocated, measured to the
     * nearest millisecond.
     * @see     java.lang.System#currentTimeMillis()
    public Date() {
        this(System.currentTimeMillis());
    }

Facing problem while calculating the difference between the two dates?

Hi
I am using this code to calculate the difference between the two dates :
import java.util.Calendar;
import java.util.*;
public class DateDifferentExample
public static void main(String[] args)
// Creates two calendars instances
Calendar cal1 = Calendar.getInstance();
Calendar cal2 = Calendar.getInstance();
// Set the date for both of the calendar instance
cal1.set(2006, 12, 30);
cal2.set(2007, 05, 03);
// Get the represented date in milliseconds
long milis1 = cal1.getTimeInMillis(); // getting error here
long milis2 = cal2.getTimeInMillis(); // getting error here
// Calculate difference in milliseconds
long diff = milis2 - milis1;
// Calculate difference in seconds
long diffSeconds = diff / 1000;
// Calculate difference in minutes
long diffMinutes = diff / (60 * 1000);
// Calculate difference in hours
long diffHours = diff / (60 * 60 * 1000);
// Calculate difference in days
long diffDays = diff / (24 * 60 * 60 * 1000);
System.out.println("In milliseconds: " + diff + " milliseconds.");
System.out.println("In seconds: " + diffSeconds + " seconds.");
System.out.println("In minutes: " + diffMinutes + " minutes.");
System.out.println("In hours: " + diffHours + " hours.");
System.out.println("In days: " + diffDays + " days.");
but i am getting this error :
The method getTimeInMillis() from the type calendar is not visible
Please suggest!!

// Get the represented date in milliseconds
long milis1 = cal1.getTime().getTime(); // getting error here
long milis2 = cal2.getTime().getTime(); // getting error here Hope this works for you!!

[svn] 4112: Further work for FXG to SWF transcoding - checking in some work resulting from collaborating with Kaushal to correct FXG transforms and gradient transforms as well as cater for differences between Java AffineTransform and the SWF Matrix type .

Revision: 4112
Author: [email protected]
Date: 2008-11-14 10:05:42 -0800 (Fri, 14 Nov 2008)
Log Message:
Further work for FXG to SWF transcoding - checking in some work resulting from collaborating with Kaushal to correct FXG transforms and gradient transforms as well as cater for differences between Java AffineTransform and the SWF Matrix type.
QE: Not yet.
Doc: No
Checkintests: Pass
Reviewer: Kaushal
Modified Paths:
flex/sdk/trunk/modules/swfutils/src/java/flash/fxg/dom/GraphicContentNode.java
flex/sdk/trunk/modules/swfutils/src/java/flash/fxg/dom/fills/LinearGradientFillNode.java
flex/sdk/trunk/modules/swfutils/src/java/flash/fxg/dom/fills/RadialGradientFillNode.java
flex/sdk/trunk/modules/swfutils/src/java/flash/fxg/dom/strokes/LinearGradientStrokeNode.j ava
flex/sdk/trunk/modules/swfutils/src/java/flash/fxg/dom/strokes/RadialGradientStrokeNode.j ava
flex/sdk/trunk/modules/swfutils/src/java/flash/fxg/swf/AbstractFXGGraphics.java
flex/sdk/trunk/modules/swfutils/src/java/flash/fxg/swf/TypeHelper.java
Added Paths:
flex/sdk/trunk/modules/swfutils/src/java/flash/fxg/dom/ScalableGradientNode.java

What are differences between Java and C#

What are differences between Java and C#?
I was looking at C# and it looks very similar to java, does anyone have any input on what the primary differences are?

C# has ventricles, being a more modern, hip,and
stylin language.Yeah, but it can't use them properly unless youbolt
on an after-market turbo charger and paint some
go-faster stripes.
Java doesn't need ventricles, as the language is
built as a bifurcative scrobbidibbit from theground
up.
And here I thought you were smart.The ventricles add power on the backswing and keep
down the humpty-B count, and those stripes don't
really do much except to impress the PHBs. A
ventricle here and there wouldn't do Java anyharm.
Oh, I see.
I didn't realize you were concerned with humpty-B. So
I suppose you put 17 firewalls in front of your VM's
Jeffries tubes too huh? And measure productivity in
fleems per wonkle?
That may have worked back when you carved FORTRAN on
stone tablets, and then went to look for a nice young
lady to club and take home. But modern software
development techniques demand a focus on the
regressive thromboid paradigm, and ventricles only
get in the way when you're trying to calibrate that
against the latest fractal suppository data.At least I have actual experience in carving FORTRAN on stone tablets, so I know what I'm talking about. (The clubbing was the other way around but that's neither here nor there.) As for your regressive thromboid paradigm, regressive is exactly what it is. Progressive paradigms, whether thromboid or rhomboid, require ventriculation to achieve their maximum potential.
And I suppose if you're still using those Jeffries tubes in your VM, it's not surprising that it's humptied to the max. Try installing Apache Fallopian if you really want to dehumptify it, or Apache Eustachian for 64-bit VMs.

Disk Utility: Differences between "Zero Out Data" and "7-Pass Erase"?

I'm wondering if anyone knows if there's a significant difference between the "Zero Out Data" erase option in Disk Utility (specifically Disk Utility 10.5.5), and the "7-Pass Erase" and "35-Pass Erase" options in same software.
Here's why I'm asking: I have a co-worker with an iMac G5 20" 1.8GHz with 160GB internal hard drive. As a result of the power supply overheating a week ago due to dust, some hard drive problems resulted. I'm trying to assess whether these are 'soft' formatting problems that can be recovered from, or 'hard' problems requiring replacement of the hard drive and/or power supply.
Following the failure, I removed the dust and restored the iMac to servicable form. The power supply seems to be OK now. The next thing was to attempt to recover as much data as possible from the 160GB, as the last full backup was a week old. Carbon Copy Cloner, shell copy via 'sudo cp -p -R -v', Finder copy, and DiskWarrior recovery all met with problems. TechTool Pro identified a huge swatch of unreadable sectors during repeated surface scans. Unfortunately, these unreadable sectors were located midway in the OSX boot partition (an 80GB partition), and not in the other 80GB partition devoted to lower priority video data.
When I was satisfied I had backed up the data to the best of my abilities, I next set out to reformat the drive and see if the bad sectors could be eliminated or remapped out of existence. I did a "Zero Out Data" erasure in Disk Utility (with no errors during the erase), but TechTool Pro showed the bad sectors persisted in equal strength at the same location. I next executed a sixteen hour "7-Pass Erase" (again no errors, and confirming that it takes about an hour per 10GB). The next day when I ran TechTool pro, all of the sector errors had disappeared. I'm a bit perplexed as to why the "7-Pass Erase" seems to have recovered the use of the drive. Is it possible that there are simply thousands of bad sectors now remapped that I'm not seeing? [If so, how do I check for this?] TechTool Pro has not reported any S.M.A.R.T. issues to date on the drive. What am I to make of that?
There are some related threads I've checked into, but I'm not sure how to properly assess my situation based on this information:
<http://discussions.apple.com/thread.jspa?threadID=232007>
<http://discussions.apple.com/thread.jspa?threadID=138559>
<http://discussions.apple.com/thread.jspa?threadID=118455>
Since the iMac has three weeks left on it's one year warranty, and I've already moved the user to another machine temporarily, I'm thinking that the smart thing to so is to send it in to Apple to have them look at the power supply and hard drive. That way, when it returns, even if there is still a lingering hardware problem, at least it will be covered under warranty for another 90 days.
Any thoughts?
iMac G5 20" 1.8GHz Mac OS X (10.4.6) 1.25GB RAM, 160GB hard disk, SuperDrive

HI, Bret.
The only differences between "Zero Out Data", "7-Pass Erase", and "35-Pass Erase" are the number of times a binary zero is written to every bit on the disk. "Zero Out Data" writes a binary zero once, whereas the 7- and 35-Pass options write a zero seven and 35 times, respectively.
Technically, one pass with Zero Out Data should be sufficient to map bad sectors out of service, a process also known as sparing. If a bad sector is encountered, it is both marked as "in use" in the directory's allocation table and added to the directory's "bad blocks file."
My understanding is that the Surface Scan of Tech Tool Pro should identify bad sectors every time it is run unless the bad sectors have been locked out by the drive controller of the ATA drive itself. This is because Surface Scan checks the entire surface of the disk.
What may have happened is that running "Zero Out Data" spared the bad blocks from a directory standpoint, but did not result in the drive's controller locking out those sectors for reasons detailed in the "Surface Scan" section of the Tech Tool Pro manual. However, the 7-Pass Erase may have resulted in the drive's controller locking out the bad sectors and why Surface Scan did not pick them up after such.
Given the problems you described, I concur with your plan to have Apple check the affected computer. You might also want to consider purchasing an AppleCare Protection Plan for that Mac: I recommend and buy these for all my Macs.
For some additional information on bad sectors, see the "Bad Sectors" section of my "Resolving Disk, Permission, and Cache Corruption" FAQ.
Good luck!
Dr. Smoke
Author: Troubleshooting Mac® OS X
Note: The information provided in the link(s) above is freely available. However, because I own The X Lab™, a commercial Web site to which some of these links point, the Apple Discussions Terms of Use require I include the following disclosure statement with this post:
I may receive some form of compensation, financial or otherwise, from my recommendation or link.

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