What is the difference between TreeMap and HashMap?

In Java, TreeMap and HashMap are both implementations of the Map interface, but they have some key differences:

• Structure: TreeMap is a type of sorted map that is implemented as a Red-Black tree, which means that the keys are sorted and stored in a hierarchical order. HashMap, on the other hand, does not guarantee any specific order of the keys.
• Performance: TreeMap offers logarithmic time complexity for key-based operations (like get, put, and remove), while HashMap provides constant time complexity on average for these operations. This makes HashMap more efficient for most cases, especially for large datasets.
• Iterations: TreeMap provides sorted iteration based on the natural order of keys or using a custom Comparator, whereas HashMap does not guarantee any specific order during iteration.
• Null keys: TreeMap does not allow null keys but allows multiple null values, while HashMap allows one null key and multiple null values.

Ultimately, the choice between TreeMap and HashMap depends on the specific requirements of the application, such as the need for sorted keys, performance considerations, and handling of null keys and values.