JDK源码-TreeMap
1，TreeMap：
-1，基于红黑树的实现。TreeMap根据创建时的顺序或者根据提供的Comparator进行排序，具体决定于使用的构造方法。提供Conparator方法后，判断对象相等也会基于此方法。
-2，containsKey，get，put和remove方法消耗log(n)的时间复杂度。
/**
*
* @(#) Main.java
* @Package com.treeMap
*
* Copyright © JING Corporation. All rights reserved.
*
*/
package com.treeMap;
import java.util.Comparator;
import java.util.TreeMap;
/**
* 类描述：
*
* @author: Jing History: Jan 23, 2015 9:32:46 AM Jing Created.
*
*/
public class Main {
public static void main(String[] args) {
TreeMap<Person, Integer> persons = new TreeMap<Person, Integer>(
new Comparator<Person>() {
@Override
public int compare(Person o1, Person o2) {
return o1.age - o2.age;
}
});
Person p1 = new Person("lisi1", 3);
Person p2 = new Person("lisi2", 31);
// Person p3 = new Person("lisi3", 3);
// Person p3 = new Person("lisi3", 15);
Person p3 = new Person("lisi1", 4);
persons.put(p1, 1);
persons.put(p2, 2);
persons.put(p3, 3);
//p3的age为3,输出 {[age= 3,name= lisi1]=3, [age= 31,name= lisi2]=2}
//p3的age为15，输出 {[age= 3,name= lisi1]=1, [age= 15,name= lisi3]=3, [age= 31,name= lisi2]=2}
//p3的age 为4，name为lisi1，p3.equals(p1)输出true，map内容为{[age= 3,name= lisi1]=1, [age= 4,name= lisi1]=3, [age= 31,name= lisi2]=2}
System.out.println(persons.toString());
System.out.println(p3.equals(p1));
}
}
class Person {
String name;
int age;
public Person(String name, int age) {
super();
this.name = name;
this.age = age;
}
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + age;
result = prime * result + ((name == null) ? 0 : name.hashCode());
return result;
}
/**
* 名称相等，则确定对象相等
*/
@Override
public boolean equals(Object obj) {
if (this == obj)
return true;
if (obj == null)
return false;
if (getClass() != obj.getClass())
return false;
final Person other = (Person) obj;
if (name == null) {
if (other.name != null)
return false;
} else if (!name.equals(other.name))
return false;
return true;
}
@Override
public String toString() {
return "[age= " + this.age + ",name= " + this.name + "]";
}
}
2，继承结构图：
3，成员变量：
-1，comparator：用来进行内部排序，如果此属性为null，则默认使用自然排序。
private final Comparator<? super K> comparator;
-2，root：树的根节点。
private transient Entry<K,V> root = null;
-3，size：树节点的数量。
private transient int size = 0;
-4，modCount：结构化修改次数。
private transient int modCount = 0;
private transient EntrySet entrySet = null;
private transient KeySet<K> navigableKeySet = null;
private transient NavigableMap<K,V> descendingMap = null;
4，主要方法：
-1，put(K, V)：
public V put(K key, V value) {Entry<K,V> t = root;//根节点if (t == null) {//根节点为空，则生成根节点// TBD:// 5045147: (coll) Adding null to an empty TreeSet should// throw NullPointerException//// compare(key, key); // type checkroot = new Entry<K,V>(key, value, null);size = 1;modCount++;return null;}int cmp;Entry<K,V> parent;// split comparator and comparable pathsComparator<? super K> cpr = comparator;if (cpr != null) {//比较器不为null，树节点插入do {parent = t;cmp = cpr.compare(key, t.key);//比较值，小于左侧，大于则放在树的右侧if (cmp < 0)t = t.left;else if (cmp > 0)t = t.right;elsereturn t.setValue(value);} while (t != null);}else {if (key == null)//比较器为nullthrow new NullPointerException();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;elsereturn t.setValue(value);} while (t != null);}Entry<K,V> e = new Entry<K,V>(key, value, parent);if (cmp < 0)parent.left = e;elseparent.right = e;fixAfterInsertion(e);//插入完成后，修改对应红黑树节点颜色size++;modCount++;//结构化修改加1return null;}
Entry对象源码:
static final class Entry<K,V> implements Map.Entry<K,V> {
K key;
V value;
Entry<K,V> left = null;//左节点
Entry<K,V> right = null;//右节点
Entry<K,V> parent;//父节点
boolean color = BLACK;//颜色
/**
* Make a new cell with given key, value, and parent, and with
* <tt>null</tt> child links, and BLACK color.
*/
Entry(K key, V value, Entry<K,V> parent) {
this.key = key;
this.value = value;
this.parent = parent;
}
TreeMap的结构，重点还是在于对红黑树的操作，所以在了解各个操作具体实现前，需要对红黑树的具体算法进行了解。