Java Collection class analysis-Treeset, java set-treeset

Java Collection class analysis-Treeset, java set-treeset

// From the source code of the treeset below, we can see that it is basically a layer of packaging of treeMap. Therefore, there are too many introductions here. For details, we can see the specific implementation of treeMap.
// Implement the NavigableSet and set interfaces. Among them, NavigableSet implements the sortSet interface public class TreeSet <E> extends AbstractSet <E> implements NavigableSet <E>, Cloneable, and java. io. serializable {// here we can see that treeset and hashset are similar to private transient NavigableMap implemented based on map <E, Object> m; // construct a private static final Object PRESENT = new Object (); TreeSet (NavigableMap <E, Object> m) {this. m = m;} // you can see that it is actually treemap public TreeSet () {thi S (new TreeMap <E, Object> () ;}// a custom Comparator created in the Policy mode, but the public TreeSet (Comparator <? Super E> comparator) {this (new TreeMap <> (comparator);} public TreeSet (Collection <? Extends E> c) {this (); addAll (c);} public TreeSet (SortedSet <E> s) {this (s. comparator (); addAll (s) ;}// the return value Iterator returns the public iterator <E> Iterator () {return m. navigableKeySet (). iterator ();} public Iterator <E> descendingIterator () {return m. descendingKeySet (). iterator ();} public NavigableSet <E> descendingSet () {return new TreeSet <> (m. descendingMap ();} public int size () {return m. siz E ();} public boolean isEmpty () {return m. isEmpty ();} // determines whether the public boolean contains (Object o) {return m. containsKey (o);} // add the public boolean add (E e) {return m. put (e, PRESENT) = null;} // Delete the public boolean remove (Object o) {return m. remove (o) = PRESENT;} // clear map public void clear () {m. clear ();} public boolean addAll (Collection <? Extends E> c) {// Use linear-time version if applicable if (m. size () = 0 & c. size ()> 0 & c instanceof SortedSet & m instanceof TreeMap) {SortedSet <? Extends E> set = (SortedSet <? Extends E>) c; TreeMap <E, Object> map = (TreeMap <E, Object>) m; Comparator <? Super E> cc = (Comparator <? Super E>) set. comparator (); Comparator <? Super E> mc = map. comparator (); if (cc = mc | (cc! = Null & cc. equals (mc) {map. addAllForTreeSet (set, PRESENT); return true ;}} return super. addAll (c);} public NavigableSet <E> subSet (E fromElement, boolean fromInclusive, E toElement, boolean tosponsive) {return new TreeSet <> (m. subMap (fromElement, fromInclusive, toElement, toInclusive);} public NavigableSet <E> headSet (E toElement, boolean intrusive) {return new TreeSet <> (m. headMap (toElemen T, random SIVE);} public NavigableSet <E> tailSet (E fromElement, boolean random SIVE) {return new TreeSet <> (m. tailMap (fromElement, inclusive);} public SortedSet <E> subSet (E fromElement, E toElement) {return subSet (fromElement, true, toElement, false );} public SortedSet <E> headSet (E toElement) {return headSet (toElement, false);} public SortedSet <E> tailSet (E fromElement) {return tailSet (fromEl Ement, true);} public Comparator <? Super E> comparator () {return m. comparator ();} public E first () {return m. firstKey ();} public E last () {return m. lastKey ();} // NavigableSet API methods public E lower (E e) {return m. lowerKey (e);} public E floor (E e) {return m. floorKey (e);} public E ceiling (E e) {return m. ceilingKey (e);} public E higher (E) {return m. higherKey (e);} public E pollFirst () {Map. entry <E,?> E = m. pollFirstEntry (); return (e = null )? Null: e. getKey ();} public E pollLast () {Map. Entry <E,?> E = m. pollLastEntry (); return (e = null )? Null: e. getKey () ;}public Object clone () {TreeSet <E> clone = null; try {clone = (TreeSet <E>) super. clone ();} catch (CloneNotSupportedException e) {throw new InternalError ();} clone. m = new TreeMap <> (m); return clone;} private void writeObject (java. io. objectOutputStream s) throws java. io. IOException {// Write out any hidden stuff s. defaultWriteObject (); // Write out Comparator s. writeObjec T (m. comparator (); // Write out size s. writeInt (m. size (); // Write out all elements in the proper order. for (E e: m. keySet () s. writeObject (e);} private void readObject (java. io. objectInputStream s) throws java. io. IOException, ClassNotFoundException {// Read in any hidden stuff s. defaultReadObject (); // Read in Comparator <? Super E> c = (Comparator <? Super E>) s. readObject (); // Create backing TreeMap <E, Object> tm; if (c = null) tm = new TreeMap <> (); else tm = new TreeMap <> (c); m = tm; // Read in size int size = s. readInt (); tm. readTreeSet (size, s, PRESENT);} private static final long serialVersionUID =-2479143000061671589L ;}