arraylist

Sort ArrayList alphabetically

I'm trying to find all permutations of a string and sort them alphabetically. This is what I have so far: public class permutations { public static void main(String args[]) { Scanner s = new Scanner(System.in); System.out.print("Enter String: "); String chars = s.next(); findPerm...

Java: ArrayList bottleneck

Hello, while profiling a java application that calculates hierarchical clustering of thousands of elements I realized that ArrayList.get occupies like half of the CPU needed in the clusterization part of the execution. The algorithm searches the two more similar elements (so it is O(n*(n+1)/2) ), here's the pseudo code: int currentMax...

How do I perform this MutliArray setup in Java?

I come from a PHP background and I'm just getting my teeth into some Java. I was wondering how I could implement the following in Java as simply as possible, just echoing the results to a terminal via the usual "System.out.print()" method. <?php $Results[0]['title'] = "No Country for Old Men"; $Results[0]['run_time'] = "122 mins"; $Resu...

Objects in Java ArrayList don't get updated.

SOLVED: This is what was wrong: current.addFolder(folder); (in the final else clause of the if statement) Added a new folder, but did not guarantee that the folder passed is the folder added, it may simply do nothing if the folder already exists, so to overcome this I changed addFolder to return the actual folder (for example if ...

Array Unique in two dimensional array in PHP

Hi I have an array that looks like this : Array ( [0] => Array ( [x] => 01 [y] => 244 ) [1] => Array ( [x] => 02 [y] => 244 ) [2] => Array ( [x] => 03 [y] => 244 ) [3] => Array ( [x] => 04 [y] => 243 ) [4] => Array ( [x] => 05 [y] => 243 ) [5] => Array ( [x] => 05 [y] => 244 ) [6] => Array ( [x] => 06 [y] => 242 ) [7] => Array ( [x] =>...

Dealing with ArrayLists in java...all members of the arraylist updating themselves?

I have a function that shrinks the size of a "Food bank" (represented by a rectangle in my GUI) once some of the food has been taken. I have the following function check for this: public boolean tryToPickUpFood(Ant a) { int xCoord = a.getLocation().x; int yCoord = a.getLocation().y; for (int i = 0; i < food...

Sax parsing from web service

Hey, I am trying to parse xml file using Sax parser. The file has variable number of same elements. I want to count the number of times the element is present. And i want this count before parsing, so that I can declare an array of appropriate size. One way is to count them in a separately class with another parser (clumsy) and other ...

Index out of bounds error

Hello, I am working on a program where i am recreating the saved widgets back on to the boundary panel. When i am creating them i am also trying to put the values into the ArrayList so that if i want to update and save the opened project i should be able to do so by getting the values from the ArrayList. Here is how the code looks like...

read ArrayList elements

Why it print the wrong output? ArrayList<String> loc = new ArrayList<String>(); This arraylist stored the value of: [topLeft, topLeft, topLeft, bottomLeft, topLeft, bottomLeft, topLeft, topLeft, Left, topLeft] the firs index 0 is = topLeft if(loc.get(1)=="topLeft") System.out.println("same") else { System.out.println("no...

Java: Bidimensional Array with methods/capabilities similar to ArrayList

I want to create an XY array of integers (or whatever type), but I want to use methods like "add", "remove", "contains", "indexOf" similar to ArrayList class. Is there any existing class with these capabilities? PS: I don't want to create an ArrayList of ArrayList ...

Find order of data inside an array

I have a simple array of stuff: $array = array("apples","oranges","strawberries"); I am trying to find the order of the stuff inside the array. (sometimes the order changes, and so do the items) I'm expecting to get something like this: "apples" => 0, "oranges => 1, "strawberries => 2 The end result has something to do with database...

How to check and match the possible combinations of arraylist elements

String [] A = {"High","Medium","Low"}; String [] B = {"High","Medium","Low"}; String [] C = {"High","Medium","Low"}; String [] D = {"High","Medium","Low"}; String [] E = {"High","Medium","Low"}; String [] F = {"High","Medium","Low"}; JComboBox Ai = new JComboBox(A); JComboBox Bi = new JComboBox(B); JComboBox Ci = new JComboBox(C); JComb...

Java Bucket Sort on Strings

I can't figure out what would be the best way to use Bucket Sort to sort a list of strings that will always be the same length. An algorithm would look like this: For the last character position down to the first: For each word in the list: Place the word into the appropriate bucket by current character For each of the ...

Why doesn't list.get(0).equals(null) work?

The first index is set to null (empty), but it doesn't print the right output, why? //set the first index as null and the rest as "High" String a []= {null,"High","High","High","High","High"}; //add array to arraylist ArrayList<Object> choice = new ArrayList<Object>(Arrays.asList(a)); for(int i=0; i<choice.size(); i++){ if(i==0){ ...

How to set arrayList size as null?

String a []= {null,null,null,null,null}; //add array to arraylist ArrayList<Object> choice = new ArrayList<Object>(Arrays.asList(a)); System.out.println(choice.size()); Why the size of the arrayList choice is 5 when all the elements have been set to null ...

How to avoid null pointer error

I trying to find whether the elements of 2 arrayLists are match or not. But this code give me error Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException since some of the elements are null. How can I solved this problem? String level []={"High","High","High","High","High","High"}; ArrayList<Object> n = new ArrayList<O...

Help matching fields between two classes

I'm not too experienced with Java yet, and I'm hoping someone can steer me in the right direction because right now I feel like I'm just beating my head against a wall... The first class is called MeasuredParams, and it's got 40+ numeric fields (height, weight, waistSize, wristSize - some int, but mostly double). The second class is a ...

java: <identifier> expected with ArrayList

I have a class named Storage. Storage contains an arraylist of special objects called Products. Each product contains information such as name, price, etc. My code is as follows: class Storage{ Product sprite = new Product("sprite",1.25,30); Product pepsi = new Product("pepsi",1.85,45); Product orange = new Product("orange",2.25,...

Cloning java ArrayList and preventing it from modifications

I have a data structure like a database Rowset, which has got Rows and Rows have Columns. I need to initialize a Columns with null values, current code is to loop thru each column for a row and initialize values to NULL. Which is very inefficient if you have 100s or rows and 10s of column. So instead I am keeping a initialized ArrayList...

Array of ArrayList Java

Hi, I am creating an PriorityQueue with multiple queues. I am using an Array to store the multiple ArrayLists that make up my different PriorityQueues. Here is what I have for my constructor so far: ArrayList<ProcessRecord> pq; ArrayList[] arrayQ; MultiList(){ arrayQ = new ArrayList[9]; pq = new ArrayList<ProcessRec...