Java's TreeMap class provides a variety of methods for managing and accessing key-value pairs in a sorted manner. Here are some of the key methods:

Basic Operations

• put(K key, V value): Inserts a mapping from the specified key to the specified value.
• get(Object key): Returns the value associated with the specified key, or null if the key is not found.
• remove(Object key): Removes the mapping for the specified key from the map.
• containsKey(Object key): Returns true if the map contains a mapping for the specified key, false otherwise.
• containsValue(Object value): Returns true if the map maps one or more keys to the specified value, false otherwise.
• clear(): Removes all mappings from the map.
• size(): Returns the number of key-value mappings in the map.
• isEmpty(): Returns true if the map contains no key-value mappings, false otherwise.

Sorted Map Specific Methods

• firstKey(): Returns the first (lowest) key currently in the map.
• lastKey(): Returns the last (highest) key currently in the map.
• firstEntry(): Returns a Map.Entry associated with the least key in the map.
• lastEntry(): Returns a Map.Entry associated with the greatest key in the map.
• pollFirstEntry(): Removes and returns a Map.Entry associated with the least key in the map.
• pollLastEntry(): Removes and returns a Map.Entry associated with the greatest key in the map.

Navigable Map Specific Methods

(for range-based operations)

• lowerEntry(K key) / lowerKey(K key): Returns the entry/key associated with the greatest key strictly less than the given key.
• floorEntry(K key) / floorKey(K key): Returns the entry/key associated with the greatest key less than or equal to the given key.
• ceilingEntry(K key) / ceilingKey(K key): Returns the entry/key associated with the least key greater than or equal to the given key.
• higherEntry(K key) / higherKey(K key): Returns the entry/key associated with the least key strictly greater than the given key.
• subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive): Returns a view of the portion of the map whose keys range from fromKey to toKey.
• headMap(K toKey, boolean inclusive): Returns a view of the portion of the map whose keys are less than (or equal to, if inclusive is true) toKey.

• tailMap(K fromKey, boolean inclusive): Returns a view of the portion of the map whose keys are greater than (or equal to, if inclusive is true) fromKey.

  View Methods

• keySet(): Returns a Set view of the keys contained in the map.
• values(): Returns a Collection view of the values contained in the map.
• entrySet(): Returns a Set view of the mappings contained in the map.
• navigableKeySet(): Returns a NavigableSet view of the keys contained in the map.
• descendingKeySet(): Returns a NavigableSet view of the keys contained in the map in descending order.
• descendingMap(): Returns a reverse order view of the mappings contained in the map.