I have been using a driver to test one of my data structures(Binary Search Tree) and i have come across this issue. -It happens when i insert more than 2 objects into the bst -What I am trying to do: I am inserting 4 objects into the tree, then i am deleting 2 objects, and then printing out my find method so that it displays whether or not it found the objects i request. for instance:
public class Driver5 {
public static void main(String[] args) {
Integer c1 = new Integer(1);
Integer c2 = new Integer(2);
Integer c3 = new Integer(3);
Integer c4 = new Integer(4);
Integer c5 = new Integer(5);
Integer c6 = new Integer(6);
Integer c7 = new Integer(7);
Integer c8 = new Integer(8);
Integer c9 = new Integer(9);
Integer c10 = new Integer(10);
Integer c11 = new Integer(11);
Integer c12 = new Integer(23);
Integer c13 = new Integer(65);
Integer c14 = new Integer(45);
Integer c15 = new Integer(18);
Integer c16 = new Integer(33);
Integer c17 = new Integer(54);
DataStructure1<Integer> theData = new DataStructure1<Integer>();
System.out.println("DS1");
long start = System.currentTimeMillis();
theData.insert(c1);
theData.insert(c2);
theData.insert(c3);
theData.insert(c4);
theData.insert(c5);
theData.insert(c6);
theData.insert(c7);
theData.insert(c8);
theData.insert(c9);
theData.insert(c10);
theData.insert(c11);
theData.insert(c12);
theData.insert(c13);
theData.insert(c14);
theData.insert(c15);
theData.insert(c16);
theData.insert(c17);
theData.delete(c2);
theData.delete(c4);
System.out.println(theData.find(c1));
System.out.println(theData.find(c2));
System.out.println(theData.find(c3));
System.out.println(theData.find(c4));
theData.delete(c2);
theData.insert(c3);
System.out.println(theData.find(c2));
System.out.println(theData.find(c3));
System.out.println(theData.find(c4));
System.out.println(theData.find(c5));
System.out.println(theData.find(c6));
System.out.println(theData.find(c7));
System.out.println(theData.find(c8));
System.out.println(theData.find(c9));
System.out.println(theData.find(c10));
System.out.println(theData.find(c11));
System.out.println(theData.find(c12));
System.out.println(theData.find(c13));
System.out.println(theData.find(c14));
System.out.println(theData.find(c15));
System.out.println(theData.find(c16));
System.out.println(theData.find(c17));
long elapsed = System.currentTimeMillis() - start;
System.out.println("The time elapsed was: " + elapsed + " ms.");
System.out.println();
BinarySearchTree<Integer> theData1 = new BinarySearchTree<Integer>();
System.out.println("BST");
long start1 = System.currentTimeMillis();
theData1.insert(c1);
theData1.insert(c2);
theData1.insert(c3);
theData1.insert(c4);
theData1.insert(c5);
theData1.insert(c6);
theData1.insert(c7);
theData1.insert(c8);
theData1.insert(c9);
theData1.insert(c10);
theData1.insert(c11);
theData1.insert(c12);
theData1.insert(c13);
theData1.insert(c14);
theData1.insert(c15);
theData1.insert(c16);
theData1.insert(c17);
theData1.delete(c2);
theData1.delete(c4);
System.out.println(theData1.find(c1));
System.out.println(theData1.find(c2));
System.out.println(theData1.find(c3));
System.out.println(theData1.find(c4));
theData1.delete(c2);
theData1.insert(c3);
System.out.println(theData1.find(c2));
System.out.println(theData1.find(c3));
System.out.println(theData1.find(c4));
System.out.println(theData1.find(c5));
System.out.println(theData1.find(c6));
System.out.println(theData1.find(c7));
System.out.println(theData1.find(c8));
System.out.println(theData1.find(c9));
System.out.println(theData1.find(c10));
System.out.println(theData1.find(c11));
System.out.println(theData1.find(c12));
System.out.println(theData1.find(c13));
System.out.println(theData1.find(c14));
System.out.println(theData1.find(c15));
System.out.println(theData1.find(c16));
System.out.println(theData1.find(c17));
long elapsed1 = System.currentTimeMillis() - start1;
System.out.println("The time elapsed was: " + elapsed1 + " ms.");
}
}
I get an error in bst at:
if( nd.getLeft() == null && nd.getRight() == null)
{
nd = null;
}
whole delete is:
public void delete(E item) {
TreeNode<E> nd = root;
while(nd != null && nd.getItem().compareTo(item) != 0)
{
if(nd.getItem().compareTo(item) < 0)
nd = nd.getRight();
else
nd = nd.getLeft();
}
if( nd.getLeft() == null && nd.getRight() == null)
{
nd = null;
}
else if(nd.getLeft() != null && nd.getRight() == null)
{
nd.setItem((E)nd.getLeft().getItem());
}
else if(nd.getLeft() == null && nd.getRight() != null)
{
nd.setItem((E)nd.getRight().getItem());
}
else if(nd.getLeft() != null && nd.getRight() != null)
{
nd.setItem((E)findsucc(nd));
}
}
if
ndisnull,then you can’t callgetLeft()on it. So make your checkSee all causes of a
NullPointerException, so that next time you encounter it, you know what to do immediately.