Message from @Jacob
Discord ID: 495337232501178388
and what is head
that's definitely messing something up
head is defined earlier
member var?
```java
public MyLinkedList() {
this.head = new ListNode(null); //with a dummy head node
this.size = 0;
}
```
okay that exception is fixed I think
maybe let's see if we can do anything with one more thing
is this linked list or tree node?
linked list
huh I get a null pointer exception from somewhere else, too
```java
------------------testAddLast()----
Exception in thread "main" java.lang.NullPointerException
at MyLinkedList$ListNode.access$2(MyLinkedList.java:11)
at MyLinkedList.add(MyLinkedList.java:205)
at MyLinkedListTester.testAddLast(MyLinkedListTester.java:42)
at MyLinkedListTester.main(MyLinkedListTester.java:214)
```
```java
public static void testAddLast() { //passed
System.out.println("------------------testAddLast()----");
init();
list3.add("A");
System.out.println(list3);
list3.add("B");
System.out.println(list3);
list3.add(null);
System.out.println(list3);
list3.add("C");
System.out.println(list3);
drawLine();
}
```
```java
//Add the object e to the end of this list.
// it returns true, after e is successfully added.
public boolean add(Object e) {
ListNode newNode = new ListNode(e);
newNode.next = null;
get(this.size - 1).next = newNode;
this.size++;
return true;
}
```
any glaring problems here?
that get() could return null
hmmm
any ideas on how to fix that?
after init()
how many nodes in list3
println after init()
what is size
should be 4
I see
list3.add("C") will throw
because last node was null
and when you get it... and attempt to set next
the data was null, not the node itself I think
ahh ok
it must be the size then
get(this.size - 1) is returning null
```
ListNode last = get(this.size - 1);
if (last != null) {
last.next = newNode;
++this.size;
return true;
}
return false;
```
thanks
this would only happen adding first node to list I would think
what is this class?
data structures?
or Java class?
Data Structures
I actually have a Java developer certificate but it was a long time ago so I have to relearn everything
Got it same time as I graduated high school
when I took that class we used C