How is the placement of leaf nodes organized in a red-black tree?

In the classic implementation of a red-black tree, leaf nodes (null nodes) are not stored as separate objects but are represented as null (or None in some languages). In Java, for example, in the standard TreeMap implementation, leaf nodes are not explicitly distinguished — missing children are simply null.

This simplifies the structure and saves memory, as there is no need to create separate objects for leaves. During balancing and traversal, it is considered that missing children are leaf nodes, which are regarded as black by definition.

Thus, leaf nodes in a red-black tree in Java are usually not stored as separate objects but are represented by the absence of a reference (null).