What type of datatype is ListNode in java?

I have encountered this datatype in java in a problem in Leetcode called ListNode and have looked up to see what ListNode does but can't find anything on it. Does anyone know what this datatype does as I'm new to Java and don't understand what it does and neither can I find any information on it.

here is the code to the problem I need to solve on leetcode:

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        
    }
}

> "... Does anyone know what this datatype does ..."

It is a custom data container; referred to as an object, in Java.
Any class structure in Java is going to be considered an object.

Although, more specifically, that data structure is called a linked list.

Here is an example of a basic object, which will contain a text value.

class ABC {
    String string = "stack overflow";
}

public static void main(String[] args) {
    ABC abc = new ABC();
    System.out.println(abc.string);
}

Output

stack overflow

And, here is an example usage of the ListNode object.

ListNode listNode = new ListNode(1);
listNode.next = new ListNode(2);
System.out.println(listNode.val);
System.out.println(listNode.next.val);

Output

1
2

That's a specific/custom class defined by LeetCode specially for the problem. It doesn't present in the JDK. The definition of class is in the doc above the class.

You can submit code to the LeetCode using that class pretending it exists and already imported. If you want to compile your code locally, there is no other way than copy-paste it from the description and put somwhere in your project.

new to Java.

I have also encountered your problem. I came across a class written by a colleague. I thought it came with jdk, so I searched for a long time in the api documentation, but I couldn't find it.

Later, I know that we can define a class ourselves according to our needs, and use this class to do some specific things.

It's like seasoning in the kitchen, there is always not enough variety.
Sometimes you have to grow some rosemary to enhance the taste of dishes.

If we need to write some classes ourselves in the future, how can we let our colleagues know its functions?
We can add the necessary comments to tell future users what this class is for, just like the code you provided:

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */