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Thread: Multi-dimension ArrayList example

  1. #1
    Super Moderator helloworld922's Avatar
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    Post Multi-dimension ArrayList example

    Here's a way to get multi dimension ArrayLists:

    In Java, you unfortunately can't create arrays of generics. However, ArrayList is basically an array, so create an ArrayList of ArrayLists.

    Here's a few basic operations on a 2d ArrayList (easily extended to any dimension).
    import java.util.ArrayList;
     
    public class ArrayList2d<Type>
    {
    	ArrayList<ArrayList<Type>>	array;
     
    	public ArrayList2d()
    	{
    		array = new ArrayList<ArrayList<Type>>();
    	}
     
    	/**
    	 * ensures a minimum capacity of num rows. Note that this does not guarantee
    	 * that there are that many rows.
    	 * 
    	 * @param num
    	 */
    	public void ensureCapacity(int num)
    	{
    		array.ensureCapacity(num);
    	}
     
    	/**
    	 * Ensures that the given row has at least the given capacity. Note that
    	 * this method will also ensure that getNumRows() >= row
    	 * 
    	 * @param row
    	 * @param num
    	 */
    	public void ensureCapacity(int row, int num)
    	{
    		ensureCapacity(row);
    		while (row < getNumRows())
    		{
    			array.add(new ArrayList<Type>());
    		}
    		array.get(row).ensureCapacity(num);
    	}
     
    	/**
    	 * Adds an item at the end of the specified row. This will guarantee that at least row rows exist.
    	 */
    	public void Add(Type data, int row)
    	{
    		ensureCapacity(row);
    		while(row >= getNumRows())
    		{
    			array.add(new ArrayList<Type>());
    		}
    		array.get(row).add(data);
    	}
     
    	public Type get(int row, int col)
    	{
    		return array.get(row).get(col);
    	}
     
    	public void set(int row, int col, Type data)
    	{
    		array.get(row).set(col,data);
    	}
     
    	public void remove(int row, int col)
    	{
    		array.get(row).remove(col);
    	}
     
    	public boolean contains(Type data)
    	{
    		for (int i = 0; i < array.size(); i++)
    		{
    			if (array.get(i).contains(data))
    			{
    				return true;
    			}
    		}
    		return false;
    	}
     
    	public int getNumRows()
    	{
    		return array.size();
    	}
     
    	public int getNumCols(int row)
    	{
    		return array.get(row).size();
    	}
    }

    edit: fixed a few bugs
    Last edited by helloworld922; January 14th, 2011 at 03:21 PM.

  2. The Following 5 Users Say Thank You to helloworld922 For This Useful Post:

    javapenguin (April 5th, 2011), JavaPF (July 23rd, 2009), Json (July 23rd, 2009), ptl161 (January 4th, 2011), svesda (October 14th, 2012)


  3. #2
    Super Moderator Json's Avatar
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    Default Re: Multi-dimension ArrayList example

    See also:

    google-collections - Project Hosting on Google Code

    // Json

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