No default construction if an allocator must be provided.
Use the given allocator for allocations.
If the given key does not exist in the TreeMap, adds it with the value defaultValue.
Inserts or overwrites the given key-value pair.
Supports treeMapkey syntax.
Supports treeMapkey = value; syntax.
Removes the key→value mapping for the given key.
A key→value mapping where the keys are guaranteed to be sorted.