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Thread: Error: Null Exception on Array of classes

  1. #1
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    Default Error: Null Exception on Array of classes

    Error:
    java.lang.NullPointerException
    	at AxisManager.CreateAxes(AxisManager.java:15)

    Axis Manager:
    public class AxisManager {
    	//store axises in array
    	//store axes order (left to right)
    	private Axis[] m_axes;
    	private int[] m_axesOrder;
     
    	public void CreateAxes(int numAxesIN){
    		m_axes = new Axis[numAxesIN];
    		m_axesOrder = new int[numAxesIN];
    		for(int i = 0; i < m_axes.length; i++){
    			System.out.println("i:"+ i); 
    			m_axesOrder[i] = i;
    			m_axes[i].SetID(i);      //<-Line 15: Error!
    		}
    	}
    }

    Axis:
    public class Axis {
    	private int m_maxScale = 0;
    	private int m_minScale = 0;
    	private int m_unit = 0; //unit measures on the scale
    	private String m_label = "";
    	private Colour m_colour = new Colour();
     
    	private String m_name ="";
    	private int m_id = 0;
     
    	private Coordinate[] m_position = new Coordinate[1]; //array 0 = top, 1=bottom
     
    	public void SetLabel(String labelIN){
    		m_label = labelIN;
    	}
     
    	public void SetMinAndMax(int minIN,int maxIN){
    		m_minScale = minIN;
    		m_maxScale = maxIN;	
    	}
     
    	public String GetLabel(){
    		return m_label;
    	}
     
    	public void SetID(int idIN){
    		m_id = idIN;
    	}
     
    }

    XML Reader to grab the data and create the Axis Manager:
     
    public class XMLReader {
     
       private PolyManager thePolyManager = new PolyManager();
       private AxisManager theAxisManager = new AxisManager();
     
       public XMLRead(String filenameIN){
          ...
          theAxisManager = new AxisManager();
          theAxisManager.CreateAxes(5);
          ...
       }				
     
    }

    The main program:
    public class TestingProcessing {
     
    	private final static String FILE_NAME = "file.xml";
     
     
    	private XMLReader objxml = new XMLReader();
     
    	private PolyManager m_mainPolyMan;
    	private AxisManager m_mainAxesMan;
     
     
    	/**
    	 * @param args
    	 */
    	public static void main(String[] args) {
     
     
    		TestingProcessing TProc = new TestingProcessing();
     
    		TProc.setXMLfile(FILE_NAME);
    		TProc.setPolyMan();
    		TProc.setAxesMan();
     
    	}
     
    	public void setPolyMan(){
    		m_mainPolyMan = objxml.getPolyMan();
    	}
     
    	public void setAxesMan(){
    		m_mainAxesMan = objxml.getAxisMan();
    	}
     
    	public void setXMLfile(String fIN){
    		  System.out.println("filename: " +  fIN);
    		objxml.XMLRead(fIN);
    	}
     
    	public XMLReader getObjXML(){
    		return objxml;
    	}
     
    }

    Why is that erroring?

    Any help would be much appreciated.

    g000we


  2. #2
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    Default Re: Error: Null Exception on Array of classes

    Solved it..

    public class AxisManager {
    	//store axises in array
    	//store axises order (left to right)
    	private Axis[] m_axes;
    	private int[] m_axesOrder;
     
    	public void CreateAxes(int numAxesIN){
    		m_axes = new Axis[numAxesIN];
    		m_axesOrder = new int[numAxesIN];
    		for(int i = 0; i < m_axes.length; i++){
    			// m_axes[i].SetID(i);
    			System.out.println("i:"+ i); 
    			m_axes[i] = new Axis();
    			m_axesOrder[i] = i;
    			m_axes[i].SetID(i);
    		}
    	}
    }

  3. #3
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    Default Re: Error: Null Exception on Array of classes

    Well done. Beat me to it
    Please use [highlight=Java] code [/highlight] tags when posting your code.
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