Rookie Question: Swap values? Declare an array and values of its indices?

Hello,
I hope this is the right forum: I have a simple Java Problem but i do not get it.
Is like that: I have to swap values within an array e.g i have one array with 3 indices. Indice 0 (the first indice) has value 12. The middle indice has no value, and the second indice has value 9. How to swap 9 to 12 and 12 to 9 without direct swap, in other words, by using the middle indice that has no value or is zero? And how do i write it in an array?
My other questions: How do i Declare an array and values of its indices?
I hope this is the right forum or site at all, in cas enot, i hope you still can help or give me links that could help. I really need this.

Hi Rookie,
     http://forum.sun.com is the best place to get answers for your queries.
     Answer to you first question:
     array[0]=array[0]+array[2]; // array[0] will have 21, because 9+12.
     array[2]=array[0]-array[2]; // array[2] will have 9, because 21-12.
     array[0]=array0]-array[2]; // array[0] will have 12, because 21-9.
     Hope your first query is resolved.
     I will answer your next query in my next reply.
Thanks & Regards,
Charan.

Similar Messages

Rookie Question! (Arrays)

Hello,
I hope this is the right forum: I have a simple Java Problem but i do not get it.
Is like that: I have to swap values within an array e.g i have one array with 3 indices. Indice 0 (the first indice) has value 12. The middle indice has no value, and the second indice has value 9. How to swap 9 to 12 and 12 to 9 without direct swap, in other words, by using the middle indice that has no value or is zero? And how do i write it in an array?
My other questions: How do i Declare an array and values of its indices?
I hope this is the right forum or site at all, in cas enot, i hope you still can help or give me links that could help. I really need this.

Please study this tutorial http://java.sun.com/docs/books/tutorial/java/data/arrays.html

Question in making an AnyType array

In this program, I am trying to copy a given AnyType array and verify that its contents are all copied in there safely... but I have been getting some errors, and have not been able to verify the reason. I would really appreciate any help from anyone. package chapter4;
public class exer20<AnyType>
     public static void main(String [] args){
          String[] ar = {"17", "13", "213", "52", "65", "7"};
          String [] ar2 = ar;
          copy(ar);
          System.out.println(check(ar2, ar));
     public static <AnyType extends Comparable<? super AnyType>> void copy(AnyType[] a){
          Object [] arr = new Object[a.length];
          AnyType[] ar = (AnyType[])arr;
          for(int i = 0; i<a.length;i++)
               ar[i] = a;
          a = ar;
     public static <AnyType extends Comparable<? super AnyType>> boolean check(AnyType[] a, AnyType[] b){
          if(a.length!=b.length) return false;
          for(int i = 0; i<a.length;i++){
               if(!a[i].equals(b[i])) return false;
          return true;
}And the error I had was Exception in thread "main" java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to [Ljava.lang.Comparable;
     at chapter4.exer20.copy(exer20.java:12)
     at chapter4.exer20.main(exer20.java:7){code}
The twelfth line being AnyType[] ar = (AnyType[])arr;.

ybjoony wrote:
Oops... yeah, that can certainly work with this problem. Thanks. But what I really want to know in this context is how I can initialize an AnyType array.
From what I knew, and from some internet search, the code was AnyType [] something = (AnyType[]) new Object[a.length], but that doesn't really give me the output... and about your question, what I meant from "AnyType" was that you can put in virtually any kind of array, like array of Integers or Characters and still get the good output.Well it will be null if it is a Object type array.You will not have to worry for the initializations,it will get initialized by default.
Thanks.

Last One I Promise! Inserting A Value In An Array And Shifting TheRest Over

Last question I have, I need to know the theory behind inserting a value into an array and shifting the rest over.. I have somewhat of an idea and that is this:
Obviously I need to use a for loop, and a temp value to hold each value until it shifts then move on to the next value? Oh and increase the size of the array by one? I'm having trouble making sense of it..
lets say we have the same array as from before
          int[] aRay = new int[5];
          aRay[0] = 1;
          aRay[1] = 9;
          aRay[2] = 3;
          aRay[3] = 4;
aRay[4] = 11;
and we want to add... lets say the element 5 into the index spot of 2 is and shift 2 to 3 and 3 to 4 and 4 to 5.
for ( int i = 0; i < aRay.length; i++) // this will move along each element of the array (so I know I need this for sure)
Am I on the right track? thanks all
Edited by: Jojobaba on May 13, 2008 11:50 PM
Edited by: Jojobaba on May 13, 2008 11:54 PM

Jojobaba wrote:
I can do all that, the only trouble I'm having right now is what's the correct way to increase the size of the array by one more? if I try to declare 4 as 5 it gives me a runtime error because 5 is out of bounds, and rightly so, because it doesn't exist
Once I get that, the rest will be cake
int[] aRay = new int[5];
^
l
l
Do I just make this a 6? or is that not the right way.. :/You can't change array sizes dynamically. You will have to make a new array of the appropriate size and copy into it. You could use copyOf: http://java.sun.com/javase/6/docs/api/java/util/Arrays.html#copyOf(int[],%20int)
I hope this is purely an academic exercise, because there's no reason to do this.

How to ask for an array and how to save the values

I'm supposed to be learning the differences between a linear search and a binary search, and the assignment is to have a user input an array and search through the array for a given number using both searches. My problem is that I know how to ask them how long they want their array to be, but I don't know how to call the getArray() method to actually ask for the contents of the array.
My code is as follows:
import java.util.Scanner;
import java.util.ArrayList;
public class Main
    private static Scanner input = new Scanner(System.in);
    public static void main (String args[])
        //creates ArrayList
        int List[];
        System.out.println("How long would you like the array to be?");
        int arrayLength = input.nextInt();
        //Initializes array list
        List = new int [arrayLength];
        System.out.println("Please enter the first value of the array");
    public static void getArray(int List[], int arrayLength)
        for(int i=0; i < arrayLength; i++) {
             System.out.println("Enter the next value for array");
             List[i] = input.nextInt();
     public static void printArray(int List[])
         for(int i=0; i < List.length; i++)
             System.out.print(List[i] + " ");
public class search
    public static int binarySearch(int anArray[], int first, int last, int value)
        int index;
        if(first > last) {
            index = -1;
        else {
            int mid = (first + last)/2;
            if(value == anArray[mid]) {
                index = mid; //value found at anArray[mid]
            else if(value < anArray[mid]) {
                //point X
                index = binarySearch(anArray, first, mid-1, value);
            else {
                //point Y
                index = binarySearch(anArray, mid+1, last, value);
            } //end if
        } //end if
        return index;
    //Iterative linear search
    public int linearSearch(int a[], int valueToFind)
        //valueToFind is the number that will be found
        //The function returns the position of the value if found
        //The function returns -1 if valueToFind was not found
        for (int i=0; i<a.length; i++) {
            if (valueToFind == a) {
return i;
return -1;

I made the changes. Two more questions.
1.) Just for curiosity, how would I have referenced those methods (called them)?
2.) How do I call the searches?
import java.util.Scanner;
import java.util.ArrayList;
public class Main
    private static Scanner input = new Scanner(System.in);
    public static void main (String args[])
        //creates ArrayList
        int List[];
        System.out.println("How many values would you like the array to have?");
        int arrayLength = input.nextInt();
        //Initializes array list
        List = new int [arrayLength];
        //Collects the array information
        for(int i=0; i < arrayLength; i++) {
             System.out.println("Enter a value for array");
             List[i] = input.nextInt();
        //Prints the array
        System.out.print("Array: ");
        for(int i=0; i < List.length; i++)
             System.out.print(List[i] + " ");
        //Asks for the value to be searched for
        System.out.println("What value would you like to search for?");
        int temp = input.nextInt();
        System.out.println(search.binarySearch()); //not working
}

Build Array and Output Values to Text or Excel File

I know this is a simple question but I need some help. I'm reading a DC voltage in LabVIEW a while loop. I want to store all the read values into an array and export that array as an text or Excel file. I had a VI that I build before for this but I cannot seem to find it and I can't remember how I did it before. Any help is appreciated. I think I can do the exporting part but I do help with building the array (storing all the data values).

I run into a problem while using the "Write to Text File Function". Initially I took about 60 measurements and wrote to a text file. That works but I increased the amount of measurements to be taken to 600 and when I did that the output in the text file are all Chinese letters (or that's what it seems like). Is this because I'm writing too much data?
When I use the "Write To Spreadsheet File VI" to write the measurments it works fine for the 600 measurements. The problem with this is I cannot insert any text. Using the "Write to Text File Function" I inserted some text before the measurements and "end of lines", to format the data. Attached is a screenshot of my VI.
Attachments:
measurements.PNG ‏45 KB

Clear array and take average of values in array continuously

I have a continuous signal that I am acquiring with hardware (sampling at 1000Hz). I want to be able to insert the data into a 1D array for 5 seconds, and then take the average of these 5000 samples. So basically, every 5 seconds I need to take the average of a 1D array and create a new array for the next 5000 samples.

There is no reason to accumulate the data into an array if all you need is the average.
Simply add the values into a shift register. Every 5000 points devide the sum by 5000, output the average, and zero the shift register for the next series of data..
LabVIEW Champion . Do more with less code and in less time .

Inserting Records in an Array and using a constructor with it

I badly need help on this! Please please please! I have been studying java for a short time only.
Anyway, here goes: My project requires the following:
Employee inputs the no. of video in the shelf. They have four classifications: Drama, Comedy, Action, and Thriller. Each video classification has different rates. The employee creates a video record containing the following information: 1. video ID number, 2. video classification, and 3. Price.
The employee should display the classifications of videos available and the price. Only the available video tapes would be displayed according to the customer's chosen classification. When the customer chooses the video he wants to rent, the program will register and attach the name of the customer to the video number.
I only need to use arrays, and NOT database to record the information.

is it ok i i declare the drama_rate outside the video class?
i have a list of variables on my videoupdate classYes. It's probably best to declare it static & then you can access it directly:
public static float drama_rate = 100.0;
rate = <the class name>.drama_rate;
so, i should also include a customer no. both in the video and customer class.I would. You may want to list a bunch of videos and who currently has them. This way you don't have to search the customers AND the videos to do this.
thanks =) i don't know either why we had to validate/invalidate,\
but our applet doesnt refresh when >it is supposed to, so
we just used this method. It wouldnt slow down the application, would it?Could you just revalidate()?
the use of arrays. i havent finished with the program yet.
i have the design already, i just couldnt put it in code.
im not familiar with the use of multidimensional arrays-
can i use this for the video and customer records i will need to store?Not sure what you're using arrays for, but here's an example of something I might do. Maybe it will be useful to you.
Have you looked at HashMaps? You could use "Customer" as the key and then use an ArrayList of checked out Videos as the value:
HashMap customers = new HashMap();
ArrayList videos = new ArrayList();
//Add the checked out videos to the list
videos.add(video);
<etc>
// Add this customer and the list of videos he has checked out.
customers.put(customer,videos);
[\code]

Converting from spreadshet string to array and then back to spreadsheet string

My questions is; why is the Spreadsheet string to array function creating more data than the original string had when you change the array back into a spreadsheet string. Im trying to analyze a comma delimited file using array functions since my column and row size is constant, but my data varies. Thus my reason for not using string parsing functions which would get more involved and difficult. So, however, after i convert to a 2D array of data from the comma delimited file I read from, and then I convert back to string using the Array to Spreadsheet String, I get added columns to the file, which prevents another program from receiving these files. Also, the data which I am reading is not all contiguous, it has gaps in some places for empty data. Looking at the file compared to the original after it has gone from string to array and then back to string again, looks almost identical except for the file size which got larger by 400 bytes and where the original file has empty spaces, the new file has a lot of commas added. Any idea?
Charles

The result you get is normal when the spreadsheet string contains rows of uneven length. Since the array rows have the same number of elements, nil values are added during the coonversion. And of course, the back to string conversion keep those added values in the string, with the associated commas.
example : 3 x 3 array
1,2,3
4
5,6,7
is converted into
1 2 3
4 0 0
5 6 7
then back to
1,2,3
4,0,0
5,6,7
Chilly Charly (aka CC)
E-List Master - Kudos glutton - Press the yellow button on the left...

Date array and Sorting

I have a date array that i created from a database. I am trying to sort the dates into the correct order with the upcoming on top.... the best would be that after the date has passed it would go to the bottom of the list. Can anyone tell me if I am on the right path with what I have so far and give me any hints? thanks (the second loop give me an error)

<cfset dateArray = arraynew(1)>

<cfloop query="CDE_Dates2">
<cfset dateArray[currentRow][1] = event_date>
</cfloop>

<cfloop index="i" from="1" to="#arrayLen(dateArray)#">
<cfset dateVar = DateFormat(dateArray[i],"YYYY/MM/DD")>
</cfloop>

I think I read that as you want dates sored in an order something like this: future dates at the top, sorted in ascending order (most imminent first to farthest future last), then past dates at the bottom in ascending order (oldest first to most recent past last).
The easiest way would be to either do this when you query the database (in your CDE_Dates2) or do a query-of-query on CDE_Dates2. You can do it using a union and adding an extra column for sorting. Here's some SQL pseudo-code:
SELECT dateColumn, otherColumn, anotherColumn, 0 AS sortOverride
FROM someTable
WHERE dateColumn > <cfqueryparam value="#Now()#" cfsqltype="cf_sql_date">
UNION
SELECT dateColumn, otherColumn, anotherColumn, 1 AS sortOverride
FROM someTable
WHERE dateColumn <= <cfqueryparam value="#Now()#" cfsqltype="cf_sql_date">
ORDER BY sortOverride, dateColumn
This will force the future dates to the top and put past dates at the bottom.
You could do the same thing in a QofQ.
-Carl V.

Read two different arrays and display

I have a text file, which has 1000 of entries in the way mentioned below:
Kozos customer
sabze employee
I am reading the content of text file and saving as an arrays.
$global:Content = get-content info.txt
$global:Name=$Content | foreach {
$hashTab=@{Name="" ; Info=""}
$hashTab.Name, $hashTab.Info=$_.Trim() -split '\s+'
New-Object PSObject -Property $hashTab
$global:Names=$ServerList | select -ExpandProperty Name
$global:Infos=$ServerList | select -ExpandProperty Info
How do I read two arrays, I mean read the values of two arrays one by one and display the result as:
Names Infos
Kozos Customer
sabze employee

We get that you are unable to do this, but it is still not clear precisely what it is that you want, a two-dimensional array, or a structure such as SeanQuinlan suggested? Also:
there seems no reason for any of the variables to be global in scope.
Where is the $serverlist variable defined?
what relationship is there between the file you mention and the data in the $serverlist variable?
Your code has three arrays, $name, $names, and $infos; which two of these do you want to combine into a single array? If $names and $infos, would this work for you:
$namesNinfos = $serverlist | select name,info
I suggest that you describe your situation without trying to state it in powershell (as that is partly where your problem lies). You could, for example, show sample content of the file and each of the two arrays, and show what this would look like in your
desired two-dimensional array, perhaps like this:
file info.txt
Kozos customer
sabze employee
array 1:
Kozos
sabze
array 2:
customer
employee
resultant 2D array
column 1 2
row
1 Kozos customer
2 sabze employee
As an aside, it could be that we are getting confused by the term "array". languages such as fortran and basic support multidimensional arrays in which each element is addressed by a set of integer indices, the most common form being row and column, as in
a spreadsheet.
In Powershell, arrays are generally one dimensional, with a single numerical index being used to select a single element ($row3 = $array[2]). That element can optionally have multiple values if it is defined as an array or a hash. This is referred to as
a "jagged array" as each element of the array may not all have the same number of sub-elements as each other.
Powershell also supports true multidimensional arrays, however, these seem fairly rarely used, I suspect because jagged arrays generally provide more easily used functionality.
You can get more details on this from
here and
here.
This, then, leads to my final question:
what type of two-dimensional array are you looking for, and how will your script be processing it?
Al Dunbar -- remember to 'mark or propose as answer' or 'vote as helpful' as appropriate.

Please tell me how can declare an array of object.

how to create a two dimentional array object of a class.
let,
class abc{
abc(){
is it posible--
abc ss=new abc[10][10]
please tell me how can declare an array object.

then always use String and don't consider
StringBuffer at the outset. 'best practices' need not
be seen as premature optimization. besides, if it is
abstracted, does not matter how it is stored
internallyNot sure I would agree with this example - a String is immutable, if I want to change the object then using a StringBuffer makes sense (conveys the intend, yada, yada, yada).
Although, I do agree with you that some optimizations are best practices and should be used. I also come from the old days when optimization was always on our mind. Also, I would not expect someone to do something like re-calculate a value every time it is needed instead of storing the value in a variable, just to avoid optimization.
I just think that the example of using a 1-dimensional array when a 2-dimentional array is a better representaion of the "real world" will both obscure the intention and compicate the code.

Declare global variable and retrive?

Hi,
we are working in live project in webtool, we wants to create global variable,
calling that variable in a required pages, our questions is that where to declare global variable and how to declare in which page we have to declare? pls guide us its very urgent and send the code.
Regards
Kannan.D
Edited by: kannan desikan on Jan 14, 2008 8:07 AM

Hi Kannan,
I would suggest using a comma delimied list or putting it in the database.
ArrayList myList = new ArrayList();
myList.Add("one");
myList.Add("two");
myList.Add("three");
string comma = "";
// store the array in the session state
foreach (string s in myList){
Session["persistedArray"] += comma + s;
comma = ",";
To get the array back
if (Session["persistedArray"] != null){
ArrayList myList = Session["persistedArray"].ToString().Split(new char[1] {','});
If your array is storing objects, you should use the database.

Deleting same elements in array and their rearrangement based on other array

I need to delete duplicating characters in a string array. In addition the rearrangement in these new string characters should depend on their position alon the X axis given in other array. Any ideas how..
Cheers,
Z
p.s. In the attachment u can see my attempt and in the help.vi u can see my attampt.
Attachments:
my attempt.png ‏29 KB
help.vi ‏7 KB

Your question is not clear.
It would help if you could place some default data into your arrays of the VI and also include an indicator containing the result you want based on the default input.
Now make the currentl values the default, then save and re-attach the VI. Thanks!
LabVIEW Champion . Do more with less code and in less time .

Newbie - help needed with array and dictionary objects

Hi all
Please see the code below. I've posted this code in another thread however the original issue was resolved and this is now a new issue I'm having although centered around the same code.
The issue is that I'm populating an array with dictionary objects. each dictionary object has a key and it's value is another array of custom objects.
I've found that the code runs without error and I end up with my array as I'm expecting however all of the dictionary objects are the same.
I assume it's something to do with pointers and/or re-using the same objects but i'm new to obj-c and pointers so i am a bit lost.
Any help again is very much appreciated.
// Open the database connection and retrieve minimal information for all objects.
- (void)initializeDatabase {
NSMutableArray *authorArray = [[NSMutableArray alloc] init];
self.authors = authorArray;
[authorArray release];
// The database is stored in the application bundle.
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *path = [documentsDirectory stringByAppendingPathComponent:@"books.sql"];
// Open the database. The database was prepared outside the application.
if (sqlite3_open([path UTF8String], &database) == SQLITE_OK) {
// Get the primary key for all books.
const char *sql = "SELECT id, author FROM author";
sqlite3_stmt *statement;
// Preparing a statement compiles the SQL query into a byte-code program in the SQLite library.
// The third parameter is either the length of the SQL string or -1 to read up to the first null terminator.
if (sqlite3preparev2(database, sql, -1, &statement, NULL) == SQLITE_OK) {
// We "step" through the results - once for each row.
// We start with Letter A...we're building an A - Z grouping
NSString *letter = @"A";
NSMutableArray *tempauthors = [[NSMutableArray alloc] init];
while (sqlite3_step(statement) == SQLITE_ROW) {
author *author = [[author alloc] init];
author.primaryKey = sqlite3columnint(statement, 0);
author.title = [NSString stringWithUTF8String:(char *)sqlite3columntext(statement, 0)];
// FOLLOWING WAS LEFT OVER FROM ORIGINAL COMMENTS IN SQLBooks example....
// We avoid the alloc-init-autorelease pattern here because we are in a tight loop and
// autorelease is slightly more expensive than release. This design choice has nothing to do with
// actual memory management - at the end of this block of code, all the book objects allocated
// here will be in memory regardless of whether we use autorelease or release, because they are
// retained by the books array.
// if the author starts with the Letter we currently have, add it to the temp array
if ([[author.title substringToIndex:1] compare:letter] == NSOrderedSame){
[tempauthors addObject:author];
} // if this is different letter, then we need to deal with that too...
else {
// create a dictionary to store the current tempauthors array in...
NSDictionary *tempDictionary = [NSDictionary dictionaryWithObject:tempauthors forKey:@"authors"];
// add the dictionary to our appDelegate-level array
[authors addObject:tempDictionary];
// now prepare for the next loop...
// set the new letter...
letter = [author.title substringToIndex:1];
// remove all of the previous authors so we don't duplicate...
[tempauthors removeAllObjects];
// add the current author as this was the one that didn't match the Letter and so
// never went into the previous array...
[tempauthors addObject:author];
// release ready for the next loop...
[author release];
// clear up the remaining authors that weren't picked up and saved in the "else" statement above...
if (tempauthors.count > 0){
NSDictionary *tempDictionary = [NSDictionary dictionaryWithObject:tempauthors forKey:@"authors"];
[authors addObject:tempDictionary];
else {
printf("Failed preparing statement %s
", sqlite3_errmsg(database));
// "Finalize" the statement - releases the resources associated with the statement.
sqlite3_finalize(statement);
} else {
// Even though the open failed, call close to properly clean up resources.
sqlite3_close(database);
NSAssert1(0, @"Failed to open database with message '%s'.", sqlite3_errmsg(database));
// Additional error handling, as appropriate...
Message was edited by: dotnetter

Ok, so I know what the issue is now...I just don't know enough to be able to resolve it!
it's the tempAuthors objects.
It's an NSMutableArray which is create on the line before the start of the WHILE loop.
Having looked through the debugger, I can see that each dictionary object is created (with different codes which I assume are memory addresses) so all is well there. However, on each iteration of the loop in the middle there is an IF...ELSE... statement which in the ELSE section is clearing all objects from the tempAuthors array and beginning to repopulate it again.
Looking at the containing dictionary objects in the debugger I can see that the tempAuthors object that each contains has the same code (again, I'm assuming this is a memory address) - so if I understand correctly, it's the same object...I assumed that when I created the dictionary using the dictionWithObject call that I would be passing in a copy of the object, but it's referencing back to the object which I then go on to change.
Assuming the above is correct, I've tried several "stabs in the dark" at fixing it.
I've tried relasing the tempAuthors object within the ELSE and initialising it again via an alloc...init - but this didn't work and again looking through the debugger it looks as though it was confused as to which object it was supposed to be using on the following iteration of the WHILE loop (it tried to access the released object).
Having read a little more about memory management can someone tell me if I'm correct in saying that the above is because the tempAuthors object is declare outside the scope of the WHILE loop yet I then try to re-instantiate it within the loop (does that make sense???).
Sorry for the long post...the more I can understand the process the less I can hopefully stop relying on others for help so much.
I am continuing to read up on memory management etc but just not there yet.
Regards
Wayne

Rookie Question: Swap values? Declare an array and values of its indices?

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