Is there anyone who can tell me why the following code sometimes (not
always) throws a NullPointerException
Using Java(TM) SE Runtime Environment (build 1.6.0_02-b06)

Node currentNode = Universe.space[i][j]; // Have checked and this is never
null.
if (currentNode.hasShip()) { // <-- This line sometimes throws a
NullPointerException
g.drawChars(Labels, 0, 1, i*GridSizeX+GridSizeX/2, j*GridSizeY);
}
if (currentNode.hasAsteroid() ) {
g.drawChars(Labels, 1, 1, i*GridSizeX+1, j*GridSizeY);
}


And here's an abbreviated version of the Node class. The local variable
localShip is never instantiated.
public class Node {


private Ship localShip;
private Asteroid localAsteroid;

boolean hasAsteroid() {
if (localAsteroid!=null)
return true;
else
return false;
}


boolean hasShip() {
if (localShip!=null)
return true;
else
return false;
}

}

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