im trying to create my own BinaryTree class and i also got a JUnit-Class which outputs the tests for the non added value and the first added value as a Nullpointer..
The Nullpointer occurs in my BinaryTree class at the while-loop, which doesnt make sense to me, as i've got the following lines of code to check it:
if(key.compareTo(current.key) == 0) {
return current.value;
}
return null;
}
The first added value should be checked first (at least i think)
Here is my code:
public class BinaryTree<K extends Comparable<K>, V>{
int count = 0;
//Please don't add any further attributes.
private K key;
private V value;
private BinaryTree<K,V> left, right;
private BinaryTree<K,V> root;
/**
* Constructor creates new BinaryTree instance, initially without child nodes.
*/
// Done!!
public BinaryTree(K key, V value){
this.value = value;
this.key = key;
left = null;
right = null;
}
/**
* Stores a key-value pair in the tree.
* If the key has already been stored, then the current value for this key
* is replaced by the new value.
*/
public void put(K key, V value) {
BinaryTree<K,V> newNode = new BinaryTree<K,V>(key, value);
if (root == null) {
root = newNode;
root.value = value;
root.key = key;
count += 1;
return;
}
BinaryTree<K,V> current = root;
BinaryTree<K,V> parent;
while (true) {
parent = current;
if (key.compareTo(current.key) == -1) {
current = current.left;
if (current == null) {
parent.left = newNode;
count += 1;
return;
}
} else {
current = current.right;
if (current == null) {
parent.right = newNode;
count += 1;
return;
}
}
}
}
/**
* Returns the value object stored with the given key.
* Returns null if the key is unknown.
*/
public V get(K key) {
BinaryTree<K,V> current = root;
while(key.compareTo(current.key) != 0) {
if(key.compareTo(current.key) < 0) {
current = current.left;
} else if(key.compareTo(current.key) > 0) {
current = current.right;
}
}
if(key.compareTo(current.key) == 0) {
return current.value;
}
return null;
}
}
