class TreeNode { public int val; public TreeNode left; public TreeNode right; }
This is similar to the original school is not fine ah! !
This is just a statement it did not create an instance
If you are a new class inside an instance and then instantiated in other places so the error will call this class
Exception in thread "main" java.lang.StackOverflowError
Here I felt struct structure inside like c ++
A closer Recall structure tmd Why did not studious = =
Structure where the write pointer and the structure pointer and array of structures of these concepts
And a structure inside the data structure pointer variable pointer field pondered what