B-树的java实现
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B-树的java实现
理论部分见：B-树的理论学习
JAVA实现
定义树结点类
/**
* B-树的结点类
*/
private static class Node
/**
* 关键字列表
*/
private final List<Object> keyList;
/**
* 孩子结点列表
*/
private final List<Node> childNodesList;
/**
* 是否叶子结点
*/
private boolean isLeaf;
/**
* 双亲结点
*/
private Node parentNode;
/**
* 键值比较函数对象，如果采用倒序或者其它排序方式，传入该对象
*/
private Comparator<Object> kComparator;
public Node()
this.keyList = new LinkedList<>();
this.childNodesList = new LinkedList<>();
this.isLeaf = false;
/**
* 自定义K排序方式的构造函数
*/
public Node(Comparator<Object> kComparator)
this();
this.kComparator = kComparator;
/**
* 比较两个key，如果没有传入自定义排序方式则采用默认的升序
*/
private int compare(Object key1, Object key2)
return this.kComparator == null ? ((Comparable<Object>) key2).compareTo(key1) : kComparator.compare(key1, key2);
public void setIsLeaf(boolean isLeaf)
this.isLeaf = isLeaf;
public boolean getIsLeaf()
return this.isLeaf;
public void setParentNode(Node parentNode)
this.parentNode = parentNode;
public Node getParentNode()
return parentNode;
/**
* 结点中关键字的个数
*/
public int keySize()
return this.keyList.size();
/**
* 采用二分查找在结点内查找关键字
*/
public SearchResult searchResult(Object key)
int begin = 0;
int end = this.keySize() - 1;
int mid = (begin + end) / 2;
boolean isExist = false;
int index = 0;
//二分查找
while (begin < end)
mid = (begin + end) / 2;
Object midValue = this.keyList.get(mid);
int compareRe = compare(midValue, key);
//找到了
if (compareRe == 0)
break;
else
if (compareRe > 0)
//在中点右边
begin = mid + 1;
else
end = mid - 1;
//二分查找结束，判断结果;三个元素以上才是正经二分，只有两个或一个元素属于边界条件要着重考虑
if (begin < end)
//找到了
isExist = true;
index = mid;
else if (begin == end)
Object midKey = this.keyList.get(begin);
int comRe = compare(midKey, key);
if (comRe == 0)
isExist = true;
index = begin;
else if (comRe > 0)
index = begin + 1;
else
index = begin;
else
index = begin;
return new SearchResult(isExist, index, null);
定义查询key的结果类
/**
* 关键字查询结果类
*/
private static class SearchResult
/**
* 关键字所在结点
*/
private final Node node;
/**
* 是否存在
*/
private final boolean isExist;
/**
* 下标
*/
private final int index;
public SearchResult(boolean isExist, int index, Node node)
this.isExist = isExist;
this.index = index;
this.node = node;
public boolean isExist()
return isExist;
public int getIndex()
return index;
public Node getNode()
return node;
定义树类
public class MyBTree
...
...
...
/**
* 默认3阶树
*/
private final Integer DEFAULT_ORDER = 3;
/**
* 树阶
*/
private int order = DEFAULT_ORDER;
/**
* 结点中关键字个数的最大值
*/
private int maxKeySize = order - 1;
/**
* 结点的最小关键字数
*/
private int nonLeafMinKeys = (int) Math.ceil(order / 2.0) - 1;
/**
* 根结点
*/
private Node root;
/**
* 比较函数对象
*/
private Comparator<Object> kComparator;
/**
* 构造一棵自然排序的B树
*/
MyBTree()
Node root = new Node();
this.root = root;
root.setIsLeaf(true);
/**
* 构造一棵order阶 的B树
*/
MyBTree(int order)
this();
this.order = order;
this.maxKeySize = order - 1;
this.nonLeafMinKeys = (int) Math.ceil(order / 2.0) - 1;
...
...
...
类图
Node和SearchResult是Btree的子类，由入口main方法执行验证。若有BUG，可以留言。
完整
package tree.b;
import java.util.*;
public class MyBTree<K>
/**
* 关键字查询结果类
*/
private static class SearchResult
/**
* 关键字所在结点
*/
private final Node node;
/**
* 是否存在
*/
private final boolean isExist;
/**
* 下标
*/
private final int index;
public SearchResult(boolean isExist, int index, Node node)
this.isExist = isExist;
this.index = index;
this.node = node;
public boolean isExist()
return isExist;
public int getIndex()
return index;
public Node getNode()
return node;
/**
* B-树的结点类
*/
private static class Node
/**
* 关键字列表
*/
private final List<Object> keyList;
/**
* 孩子结点列表
*/
private final List<Node> childNodesList;
/**
* 是否叶子结点
*/
private boolean isLeaf;
/**
* 双亲结点
*/
private Node parentNode;
/**
* 键值比较函数对象，如果采用倒序或者其它排序方式，传入该对象
*/
private Comparator<Object> kComparator;
public Node()
this.keyList = new LinkedList<>();
this.childNodesList = new LinkedList<>();
this.isLeaf = false;
/**
* 自定义K排序方式的构造函数
*/
public Node(Comparator<Object> kComparator)
this();
this.kComparator = kComparator;
/**
* 比较两个key，如果没有传入自定义排序方式则采用默认的升序
*/
private int compare(Object key1, Object key2)
return this.kComparator == null ? ((Comparable<Object>) key2).compareTo(key1) : kComparator.compare(key1, key2);
public void setIsLeaf(boolean isLeaf)
this.isLeaf = isLeaf;
public boolean getIsLeaf()
return this.isLeaf;
public void setParentNode(Node parentNode)
this.parentNode = parentNode;
public Node getParentNode()
return parentNode;
/**
* 结点中关键字的个数
*/
public int keySize()
return this.keyList.size();
/**
* 采用二分查找在结点内查找关键字
*/
public SearchResult searchResult(Object key)
int begin = 0;
int end = this.keySize() - 1;
int mid = (begin + end) / 2;
boolean isExist = false;
int index = 0;
//二分查找
while (begin < end)
mid = (begin + end) / 2;
Object midValue = this.keyList.get(mid);
int compareRe = compare(midValue, key);
//找到了
if (compareRe == 0)
break;
else
if (compareRe > 0)
//在中点右边
begin = mid + 1;
else
end = mid - 1;
//二分查找结束，判断结果;三个元素以上才是正经二分，只有两个或一个元素属于边界条件要着重考虑
if (begin < end)
//找到了
isExist = true;
index = mid;
else if (begin == end)
Object midKey = this.keyList.get(begin);
int comRe = compare(midKey, key);
if (comRe == 0)
isExist = true;
index = begin;
else if (comRe > 0)
index = begin + 1;
else
index = begin;
else
index = begin;
return new SearchResult(isExist, index, null);
/**
* 默认3阶树
*/
private final Integer DEFAULT_ORDER = 3;
/**
* 树阶
*/
private int order = DEFAULT_ORDER;
/**
* 结点中关键字个数的最大值
*/
private int maxKeySize = order - 1;
/**
* 结点的最小关键字数
*/
private int nonLeafMinKeys = (int) Math.ceil(order / 2.0) - 1;
/**
* 根结点
*/
private Node root;
/**
* 比较函数对象
*/
private Comparator<Object> kComparator;
/**
* 构造一棵自然排序的B树
*/
MyBTree()
Node root = new Node();
this.root = root;
root.setIsLeaf(true);
/**
* 构造一棵order阶 的B树
*/
MyBTree(int order)
this();
this.order = order;
this.maxKeySize = order - 1;
this.nonLeafMinKeys = (int) Math.ceil(order / 2.0) - 1;
/**
* 在以node为根的树内搜索key项
*/
private SearchResult search(Node node, Object key)
SearchResult re = node.searchResult(key);
if (re.isExist())
return new SearchResult(true, re.getIndex(), node);
else
// 叶子结点
if (node.getIsLeaf())
return new SearchResult(false, re.getIndex(), node);
int index = re.getIndex();
//递归搜索子结点--index是在查询结点内关键字的下标 也是子结点的下标
return search(node.childNodesList.get(index), key);
public boolean insertKey(Object key)
// 查询key在树中的结点情况
SearchResult searchResult = search(root, key);
if (searchResult.isExist())
//已存在key，直接返回
return false;
// 找出根结点
if (null == searchResult.getNode().parentNode)
return insertKey(root, searchResult.getIndex(), key);
else
return insertKey(searchResult.getNode(), searchResult.getIndex(), key);
private boolean insertKey(Node node, int index, Object key)
node.keyList.add(index, key);
if (node.keyList.size() > maxKeySize)
// 分裂
splitNode(node);
return true;
/**
* 分裂结点
*/
private void splitNode(Node node)
//取结点中间key下标
int midIndex = node.keyList.size() / 2;
Object key = node.keyList.get(midIndex);
Node newNode = new Node();以上是关于B-树的java实现的主要内容，如果未能解决你的问题，请参考以下文章