Java集合源码学习(21)_Map接口子接口SortedMap和NavigableMap

1：SortedMap继承自Map接口，增加了按顺序操作的几个方法;

2：排序是按照key的自然顺序(必须实现Comparable)或者指定的Comparator

Method Summary
Comparator<? superK>	comparator()            Returns the comparator used to order the keys in this map, or null if this map uses the natural ordering of its keys.
Set<Map.Entry<K,V>>	entrySet()            Returns a Set view of the mappings contained in this map.
K	firstKey()            Returns the first (lowest) key currently in this map.
SortedMap<K,V>	headMap(K toKey)            Returns a view of the portion of this map whose keys are strictly less than toKey.
Set<K>	keySet()            Returns a Set view of the keys contained in this map.
K	lastKey()            Returns the last (highest) key currently in this map.
SortedMap<K,V>	subMap(K fromKey, K toKey)            Returns a view of the portion of this map whose keys range from fromKey, inclusive, to toKey, exclusive.
SortedMap<K,V>	tailMap(K fromKey)            Returns a view of the portion of this map whose keys are greater than or equal to fromKey.
Collection<V>	values()            Returns a Collection view of the values contained in this map.

1：NavigableMap继承了SortedMap

Method Summary
Comparator<? superK>	comparator()            Returns the comparator used to order the keys in this map, or null if this map uses the natural ordering of its keys.
Set<Map.Entry<K,V>>	entrySet()            Returns a Set view of the mappings contained in this map.
K	firstKey()            Returns the first (lowest) key currently in this map.
SortedMap<K,V>	headMap(K toKey)            Returns a view of the portion of this map whose keys are strictly less than toKey.
Set<K>	keySet()            Returns a Set view of the keys contained in this map.
K	lastKey()            Returns the last (highest) key currently in this map.
SortedMap<K,V>	subMap(K fromKey, K toKey)            Returns a view of the portion of this map whose keys range from fromKey, inclusive, to toKey, exclusive.
SortedMap<K,V>	tailMap(K fromKey)            Returns a view of the portion of this map whose keys are greater than or equal to fromKey.
Collection<V>	values()            Returns a Collection view of the values contained in this map.

Method Summary
Map.Entry<K,V>	ceilingEntry(K key)            Returns a key-value mapping associated with the least key greater than or equal to the given key, or nullif there is no such key.
K	ceilingKey(K key)            Returns the least key greater than or equal to the given key, or null if there is no such key.
NavigableSet<K>	descendingKeySet()            Returns a reverse order NavigableSet view of the keys contained in this map.
NavigableMap<K,V>	descendingMap()            Returns a reverse order view of the mappings contained in this map.
Map.Entry<K,V>	firstEntry()            Returns a key-value mapping associated with the least key in this map, or null if the map is empty.
Map.Entry<K,V>	floorEntry(K key)            Returns a key-value mapping associated with the greatest key less than or equal to the given key, or nullif there is no such key.
K	floorKey(K key)            Returns the greatest key less than or equal to the given key, or null if there is no such key.
SortedMap<K,V>	headMap(K toKey)            Returns a view of the portion of this map whose keys are strictly less than toKey.
NavigableMap<K,V>	headMap(K toKey, boolean inclusive)            Returns a view of the portion of this map whose keys are less than (or equal to, if inclusive is true)toKey.
Map.Entry<K,V>	higherEntry(K key)            Returns a key-value mapping associated with the least key strictly greater than the given key, or null if there is no such key.
K	higherKey(K key)            Returns the least key strictly greater than the given key, or null if there is no such key.
Map.Entry<K,V>	lastEntry()            Returns a key-value mapping associated with the greatest key in this map, or null if the map is empty.
Map.Entry<K,V>	lowerEntry(K key)            Returns a key-value mapping associated with the greatest key strictly less than the given key, or null if there is no such key.
K	lowerKey(K key)            Returns the greatest key strictly less than the given key, or null if there is no such key.
NavigableSet<K>	navigableKeySet()            Returns a NavigableSet view of the keys contained in this map.
Map.Entry<K,V>	pollFirstEntry()            Removes and returns a key-value mapping associated with the least key in this map, or null if the map is empty.
Map.Entry<K,V>	pollLastEntry()            Removes and returns a key-value mapping associated with the greatest key in this map, or null if the map is empty.
NavigableMap<K,V>	subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive)            Returns a view of the portion of this map whose keys range from fromKey to toKey.
SortedMap<K,V>	subMap(K fromKey, K toKey)            Returns a view of the portion of this map whose keys range from fromKey, inclusive, to toKey, exclusive.
SortedMap<K,V>	tailMap(K fromKey)            Returns a view of the portion of this map whose keys are greater than or equal to fromKey.
NavigableMap<K,V>	tailMap(K fromKey, boolean inclusive)            Returns a view of the portion of this map whose keys are greater than (or equal to, if inclusive is true)fromKey.

Method Summary
Comparator<? superK>	comparator()            Returns the comparator used to order the keys in this map, or null if this map uses the natural ordering of its keys.
Set<Map.Entry<K,V>>	entrySet()            Returns a Set view of the mappings contained in this map.
K	firstKey()            Returns the first (lowest) key currently in this map.
SortedMap<K,V>	headMap(K toKey)            Returns a view of the portion of this map whose keys are strictly less than toKey.
Set<K>	keySet()            Returns a Set view of the keys contained in this map.
K	lastKey()            Returns the last (highest) key currently in this map.
SortedMap<K,V>	subMap(K fromKey, K toKey)            Returns a view of the portion of this map whose keys range from fromKey, inclusive, to toKey, exclusive.
SortedMap<K,V>	tailMap(K fromKey)            Returns a view of the portion of this map whose keys are greater than or equal to fromKey.
Collection<V>	values()            Returns a Collection view of the values contained in this map.

Method Summary
Map.Entry<K,V>	ceilingEntry(K key)            Returns a key-value mapping associated with the least key greater than or equal to the given key, or nullif there is no such key.
K	ceilingKey(K key)            Returns the least key greater than or equal to the given key, or null if there is no such key.
NavigableSet<K>	descendingKeySet()            Returns a reverse order NavigableSet view of the keys contained in this map.
NavigableMap<K,V>	descendingMap()            Returns a reverse order view of the mappings contained in this map.
Map.Entry<K,V>	firstEntry()            Returns a key-value mapping associated with the least key in this map, or null if the map is empty.
Map.Entry<K,V>	floorEntry(K key)            Returns a key-value mapping associated with the greatest key less than or equal to the given key, or nullif there is no such key.
K	floorKey(K key)            Returns the greatest key less than or equal to the given key, or null if there is no such key.
SortedMap<K,V>	headMap(K toKey)            Returns a view of the portion of this map whose keys are strictly less than toKey.
NavigableMap<K,V>	headMap(K toKey, boolean inclusive)            Returns a view of the portion of this map whose keys are less than (or equal to, if inclusive is true)toKey.
Map.Entry<K,V>	higherEntry(K key)            Returns a key-value mapping associated with the least key strictly greater than the given key, or null if there is no such key.
K	higherKey(K key)            Returns the least key strictly greater than the given key, or null if there is no such key.
Map.Entry<K,V>	lastEntry()            Returns a key-value mapping associated with the greatest key in this map, or null if the map is empty.
Map.Entry<K,V>	lowerEntry(K key)            Returns a key-value mapping associated with the greatest key strictly less than the given key, or null if there is no such key.
K	lowerKey(K key)            Returns the greatest key strictly less than the given key, or null if there is no such key.
NavigableSet<K>	navigableKeySet()            Returns a NavigableSet view of the keys contained in this map.
Map.Entry<K,V>	pollFirstEntry()            Removes and returns a key-value mapping associated with the least key in this map, or null if the map is empty.
Map.Entry<K,V>	pollLastEntry()            Removes and returns a key-value mapping associated with the greatest key in this map, or null if the map is empty.
NavigableMap<K,V>	subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive)            Returns a view of the portion of this map whose keys range from fromKey to toKey.
SortedMap<K,V>	subMap(K fromKey, K toKey)            Returns a view of the portion of this map whose keys range from fromKey, inclusive, to toKey, exclusive.
SortedMap<K,V>	tailMap(K fromKey)            Returns a view of the portion of this map whose keys are greater than or equal to fromKey.
NavigableMap<K,V>	tailMap(K fromKey, boolean inclusive)            Returns a view of the portion of this map whose keys are greater than (or equal to, if inclusive is true)fromKey.