版权声明：本文为博主原创文章，转载添加原文链接 https://blog.csdn.net/qq_34190023/article/details/80879393
内部最后会存在左旋和右旋的问题
public class TreeMap<K,V> extends AbstractMap<K,V> implements NavigableMap<K,V>, Cloneable, java.io.Serializable{
private final Comparator<? super K> comparator;// 维护了比较 private transient Entry<K,V> root; private transient int size = 0; private transient int modCount = 0;
public TreeMap(Map<? extends K, ? extends V> m) { comparator = null; putAll(m); }
public TreeMap(SortedMap<K, ? extends V> m) { comparator = m.comparator(); try { buildFromSorted(m.size(), m.entrySet().iterator(), null, null); } catch (java.io.IOException cannotHappen) { } catch (ClassNotFoundException cannotHappen) { } }
public V get(Object key) { Entry<K,V> p = getEntry(key); return (p==null ? null : p.value); }
final Entry<K,V> getEntry(Object key) { // Offload comparator-based version for sake of performance if (comparator != null) return getEntryUsingComparator(key); // if (key == null) throw new NullPointerException(); @SuppressWarnings("unchecked") Comparable<? super K> k = (Comparable<? super K>) key; Entry<K,V> p = root; while (p != null) { int cmp = k.compareTo(p.key); if (cmp < 0) p = p.left; else if (cmp > 0) p = p.right; else return p; } return null; }
final Entry<K,V> getEntryUsingComparator(Object key) { @SuppressWarnings("unchecked") K k = (K) key; Comparator<? super K> cpr = comparator; if (cpr != null) { Entry<K,V> p = root; while (p != null) { int cmp = cpr.compare(k, p.key); if (cmp < 0) p = p.left; else if (cmp > 0) p = p.right; else return p; } } return null; }
public V put(K key, V value) { Entry<K,V> t = root; if (t == null) { compare(key, key); // type (and possibly null) check root = new Entry<>(key, value, null); size = 1; modCount++; return null; } int cmp; Entry<K,V> parent; // split comparator and comparable paths Comparator<? super K> cpr = comparator; if (cpr != null) { do { parent = t; cmp = cpr.compare(key, t.key); if (cmp < 0) t = t.left; else if (cmp > 0) t = t.right; else return t.setValue(value); } while (t != null); } else { if (key == null) throw new NullPointerException(); @SuppressWarnings("unchecked") Comparable<? super K> k = (Comparable<? super K>) key; do { parent = t; cmp = k.compareTo(t.key); if (cmp < 0) t = t.left; else if (cmp > 0) t = t.right; else return t.setValue(value); } while (t != null); } Entry<K,V> e = new Entry<>(key, value, parent); if (cmp < 0) parent.left = e; else parent.right = e; fixAfterInsertion(e); size++; modCount++; return null; }
public void putAll(Map<? extends K, ? extends V> map) { int mapSize = map.size(); if (size==0 && mapSize!=0 && map instanceof SortedMap) { Comparator<?> c = ((SortedMap<?,?>)map).comparator(); if (c == comparator || (c != null && c.equals(comparator))) { ++modCount; try { buildFromSorted(mapSize, map.entrySet().iterator(), null, null); } catch (java.io.IOException cannotHappen) { } catch (ClassNotFoundException cannotHappen) { } return; } } super.putAll(map); }
public V remove(Object key) { Entry<K,V> p = getEntry(key); if (p == null) return null; V oldValue = p.value; deleteEntry(p); return oldValue; }
public void clear() { modCount++; size = 0; root = null; }
public Object clone() { TreeMap<?,?> clone; try { clone = (TreeMap<?,?>) super.clone(); } catch (CloneNotSupportedException e) { throw new InternalError(e); } // Put clone into "virgin" state (except for comparator) clone.root = null; clone.size = 0; clone.modCount = 0; clone.entrySet = null; clone.navigableKeySet = null; clone.descendingMap = null; // Initialize clone with our mappings try { clone.buildFromSorted(size, entrySet().iterator(), null, null); } catch (java.io.IOException cannotHappen) { } catch (ClassNotFoundException cannotHappen) { } return clone; }
static final class Entry<K,V> implements Map.Entry<K,V> { K key; V value; Entry<K,V> left; Entry<K,V> right; Entry<K,V> parent; boolean color = BLACK; Entry(K key, V value, Entry<K,V> parent) { this.key = key; this.value = value; this.parent = parent; } public K getKey() { return key; } public V getValue() { return value; } public V setValue(V value) { V oldValue = this.value; this.value = value; return oldValue; } public boolean equals(Object o) { if (!(o instanceof Map.Entry)) return false; Map.Entry<?,?> e = (Map.Entry<?,?>)o; return valEquals(key,e.getKey()) && valEquals(value,e.getValue()); } public int hashCode() { int keyHash = (key==null ? 0 : key.hashCode()); int valueHash = (value==null ? 0 : value.hashCode()); return keyHash ^ valueHash; } public String toString() { return key + "=" + value; } }
private void fixAfterInsertion(Entry<K,V> x) { x.color = RED; while (x != null && x != root && x.parent.color == RED) { if (parentOf(x) == leftOf(parentOf(parentOf(x)))) { Entry<K,V> y = rightOf(parentOf(parentOf(x))); if (colorOf(y) == RED) { setColor(parentOf(x), BLACK); setColor(y, BLACK); setColor(parentOf(parentOf(x)), RED); x = parentOf(parentOf(x)); } else { if (x == rightOf(parentOf(x))) { x = parentOf(x); rotateLeft(x); } setColor(parentOf(x), BLACK); setColor(parentOf(parentOf(x)), RED); rotateRight(parentOf(parentOf(x))); } } else { Entry<K,V> y = leftOf(parentOf(parentOf(x))); if (colorOf(y) == RED) { setColor(parentOf(x), BLACK); setColor(y, BLACK); setColor(parentOf(parentOf(x)), RED); x = parentOf(parentOf(x)); } else { if (x == leftOf(parentOf(x))) { x = parentOf(x); rotateRight(x); } setColor(parentOf(x), BLACK); setColor(parentOf(parentOf(x)), RED); rotateLeft(parentOf(parentOf(x))); } } } root.color = BLACK; }
如果叔叔为空，那么就将root进行左旋，root变成原来的叔叔，爸爸变成root，儿子变成原来的爸爸。然后就平衡了、为了方便检索，需要平衡，防止退回到链表