java TreeMap源码解析详解

 private final Comparator<? super K> comparator;

  public TreeMap() {comparator = null;}

  public TreeMap(Comparator<? super K> comparator) {
    this.comparator = comparator;
  } 

private final Comparator<? super K> comparator;
private transient Entry<K,V> root;
private transient int modCount = 0;
//静态成员内部类
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;
    .........
   }

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 V remove(Object key) {
    Entry<K,V> p = getEntry(key);
    if (p == null)
      return null;

    V oldValue = p.value;
    deleteEntry(p);
    return oldValue;
  }

 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;
  }

/*代码虽多，我们一点一点看*/
  private void deleteEntry(Entry<K,V> p) {
    modCount++;
    size--;

    // If strictly internal, copy successor's element to p and then make p
    // point to successor.
    if (p.left != null && p.right != null) {
      Entry<K,V> s = successor(p);
      p.key = s.key;
      p.value = s.value;
      p = s;
    } // p has 2 children

    // Start fixup at replacement node, if it exists.
    Entry<K,V> replacement = (p.left != null ? p.left : p.right);

    if (replacement != null) {
      // Link replacement to parent
      replacement.parent = p.parent;
      if (p.parent == null)
        root = replacement;
      else if (p == p.parent.left)
        p.parent.left = replacement;
      else
        p.parent.right = replacement;

      // Null out links so they are OK to use by fixAfterDeletion.
      p.left = p.right = p.parent = null;

      // Fix replacement
      if (p.color == BLACK)
        fixAfterDeletion(replacement);
    } else if (p.parent == null) { // return if we are the only node.
      root = null;
    } else { // No children. Use self as phantom replacement and unlink.
      if (p.color == BLACK)
        fixAfterDeletion(p);

      if (p.parent != null) {
        if (p == p.parent.left)
          p.parent.left = null;
        else if (p == p.parent.right)
          p.parent.right = null;
        p.parent = null;
      }
    }
  }