java.lang.Object

cloud.opencode.base.collections.MapUtil

public final class MapUtil extends Object

MapUtil - Map Utility Class MapUtil - 映射工具类

Provides factory methods and operations for Map implementations including HashMap, LinkedHashMap, TreeMap, and ConcurrentMap.

提供 Map 实现的工厂方法和操作，包括 HashMap、LinkedHashMap、TreeMap 和 ConcurrentMap。

Features | 主要功能:

Factory methods for map creation - Map 创建工厂方法
Map difference calculation - Map 差异计算
Transformation views - 转换视图
Filtering views - 过滤视图

Usage Examples | 使用示例:

// Create HashMap - 创建 HashMap
Map<String, Integer> map = MapUtil.newHashMap();

// Unique index - 唯一索引
Map<String, User> byId = MapUtil.uniqueIndex(users, User::getId);

// Map difference - Map 差异
MapDifference<String, Integer> diff = MapUtil.difference(map1, map2);

// Transform values - 转换值
Map<String, String> stringValues = MapUtil.transformValues(map, Object::toString);

Performance | 性能特性:

Factory methods: O(1) or O(n) - 工厂方法: O(1) 或 O(n)
uniqueIndex: O(n) - uniqueIndex: O(n)
difference: O(n + m) - difference: O(n + m)

Security | 安全性:

Thread-safe: No (except ConcurrentMap) - 线程安全: 否（ConcurrentMap 除外）
Null-safe: Yes - 空值安全: 是

Since:

JDK 25, opencode-base-collections V1.0.0

Author:

Leon Soo www.LeonSoo.com

See Also:

Nested Class Summary

Nested Classes

Modifier and Type

Class

Description

static interface

MapUtil.EntryTransformer<K,V1,V2>

Entry transformer interface 条目转换器
Method Summary

Modifier and Type

Method

Description

static int

capacity(int expectedSize)

Calculate capacity for expected size 计算 HashMap 所需容量

static <K,V> MapDifference<K,V>

difference(Map<? extends K, ? extends V> left, Map<? extends K, ? extends V> right)

Compute the difference between two maps 计算两个 Map 的差异

static <K,V> MapDifference<K,V>

difference(Map<? extends K, ? extends V> left, Map<? extends K, ? extends V> right, Equivalence<? super V> valueEquivalence)

Calculate the difference between two maps using custom value equivalence.

static <K,V> Map<K,V>

filterEntries(Map<K,V> unfiltered, Predicate<? super Map.Entry<K,V>> entryPredicate)

Return a view filtered by entries 过滤条目视图

static <K,V> Map<K,V>

filterKeys(Map<K,V> unfiltered, Predicate<? super K> keyPredicate)

Return a view filtered by keys 过滤键视图

static <K,V> Map<K,V>

filterValues(Map<K,V> unfiltered, Predicate<? super V> valuePredicate)

Return a view filtered by values 过滤值视图

static Map<String,String>

fromProperties(Properties properties)

Create a Properties object to Map 从属性创建 Map

static <K,V> Map.Entry<K,V>

immutableEntry(K key, V value)

Create an immutable entry 创建不可变条目

static <K,V> ConcurrentMap<K,V>

newConcurrentMap()

Create a new ConcurrentMap 创建 ConcurrentMap

static <K,V> HashMap<K,V>

newHashMap()

Create a new HashMap 创建 HashMap

static <K,V> HashMap<K,V>

newHashMap(Map<? extends K, ? extends V> map)

Create a new HashMap from an existing Map 从 Map 创建 HashMap

static <K,V> HashMap<K,V>

newHashMapWithExpectedSize(int expectedSize)

Create a new HashMap with expected size 创建指定容量的 HashMap

static <K,V> IdentityHashMap<K,V>

newIdentityHashMap()

Create a new IdentityHashMap 创建 IdentityHashMap

static <K,V> LinkedHashMap<K,V>

newLinkedHashMap()

Create a new LinkedHashMap 创建 LinkedHashMap

static <K,V> LinkedHashMap<K,V>

newLinkedHashMapWithExpectedSize(int expectedSize)

Create a new LinkedHashMap with expected size 创建指定容量的 LinkedHashMap

static <K extends Comparable<K>, V> TreeMap<K,V>

newTreeMap()

Create a new TreeMap 创建 TreeMap

static <K,V> TreeMap<K,V>

newTreeMap(Comparator<? super K> comparator)

Create a new TreeMap with comparator 带比较器的 TreeMap

static <K,V> BiMap<K,V>

synchronizedBiMap(BiMap<K,V> bimap)

Create a synchronized BiMap wrapper.

static <K,V1,V2> Map<K,V2>

transformEntries(Map<K,V1> fromMap, MapUtil.EntryTransformer<? super K, ? super V1, V2> transformer)

Return a view with transformed entries 转换条目视图

static <K,V1,V2> Map<K,V2>

transformValues(Map<K,V1> fromMap, Function<? super V1, V2> function)

Return a view with transformed values 转换值视图

static <K,V> Map<K,V>

uniqueIndex(Iterable<V> values, Function<? super V, K> keyFunction)

Create a map indexed by unique keys extracted from values 按唯一键索引

static <K,V> Map<K,V>

uniqueIndex(Iterator<V> values, Function<? super V, K> keyFunction)

Create a map indexed by unique keys extracted from values 按唯一键索引（Iterator）

static <K,V> BiMap<K,V>

unmodifiableBiMap(BiMap<? extends K, ? extends V> bimap)

Create an unmodifiable BiMap wrapper.

Methods inherited from class Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Details
- newHashMap
  
  public static <K,V> HashMap<K,V> newHashMap()
  
  Create a new HashMap 创建 HashMap
  
  Type Parameters:
  
  K - key type | 键类型
  
  V - value type | 值类型
  
  Returns:
  
  new HashMap | 新的 HashMap
- newHashMap
  
  public static <K,V> HashMap<K,V> newHashMap(Map<? extends K, ? extends V> map)
  
  Create a new HashMap from an existing Map 从 Map 创建 HashMap
  
  Type Parameters:
  
  K - key type | 键类型
  
  V - value type | 值类型
  
  Parameters:
  
  map - source map | 源 Map
  
  Returns:
  
  new HashMap | 新的 HashMap
- newHashMapWithExpectedSize
  
  public static <K,V> HashMap<K,V> newHashMapWithExpectedSize(int expectedSize)
  
  Create a new HashMap with expected size 创建指定容量的 HashMap
  
  Type Parameters:
  
  K - key type | 键类型
  
  V - value type | 值类型
  
  Parameters:
  
  expectedSize - expected size | 预期大小
  
  Returns:
  
  new HashMap | 新的 HashMap
- newLinkedHashMap
  
  public static <K,V> LinkedHashMap<K,V> newLinkedHashMap()
  
  Create a new LinkedHashMap 创建 LinkedHashMap
  
  Type Parameters:
  
  K - key type | 键类型
  
  V - value type | 值类型
  
  Returns:
  
  new LinkedHashMap | 新的 LinkedHashMap
- newLinkedHashMapWithExpectedSize
  
  public static <K,V> LinkedHashMap<K,V> newLinkedHashMapWithExpectedSize(int expectedSize)
  
  Create a new LinkedHashMap with expected size 创建指定容量的 LinkedHashMap
  
  Type Parameters:
  
  K - key type | 键类型
  
  V - value type | 值类型
  
  Parameters:
  
  expectedSize - expected size | 预期大小
  
  Returns:
  
  new LinkedHashMap | 新的 LinkedHashMap
- newTreeMap
  
  public static <K extends Comparable<K>, V> TreeMap<K,V> newTreeMap()
  
  Create a new TreeMap 创建 TreeMap
  
  Type Parameters:
  
  K - key type | 键类型
  
  V - value type | 值类型
  
  Returns:
  
  new TreeMap | 新的 TreeMap
- newTreeMap
  
  public static <K,V> TreeMap<K,V> newTreeMap(Comparator<? super K> comparator)
  
  Create a new TreeMap with comparator 带比较器的 TreeMap
  
  Type Parameters:
  
  K - key type | 键类型
  
  V - value type | 值类型
  
  Parameters:
  
  comparator - the comparator | 比较器
  
  Returns:
  
  new TreeMap | 新的 TreeMap
- newConcurrentMap
  
  public static <K,V> ConcurrentMap<K,V> newConcurrentMap()
  
  Create a new ConcurrentMap 创建 ConcurrentMap
  
  Type Parameters:
  
  K - key type | 键类型
  
  V - value type | 值类型
  
  Returns:
  
  new ConcurrentMap | 新的 ConcurrentMap
- newIdentityHashMap
  
  public static <K,V> IdentityHashMap<K,V> newIdentityHashMap()
  
  Create a new IdentityHashMap 创建 IdentityHashMap
  
  Type Parameters:
  
  K - key type | 键类型
  
  V - value type | 值类型
  
  Returns:
  
  new IdentityHashMap | 新的 IdentityHashMap
- uniqueIndex
  
  public static <K,V> Map<K,V> uniqueIndex(Iterable<V> values, Function<? super V, K> keyFunction)
  
  Create a map indexed by unique keys extracted from values 按唯一键索引
  
  Type Parameters:
  
  K - key type | 键类型
  
  V - value type | 值类型
  
  Parameters:
  
  values - the values | 值
  
  keyFunction - the key extractor | 键提取器
  
  Returns:
  
  indexed map | 索引后的 Map
  
  Throws:
  
  OpenCollectionException - if duplicate keys | 如果有重复键
- uniqueIndex
  
  public static <K,V> Map<K,V> uniqueIndex(Iterator<V> values, Function<? super V, K> keyFunction)
  
  Create a map indexed by unique keys extracted from values 按唯一键索引（Iterator）
  
  Type Parameters:
  
  K - key type | 键类型
  
  V - value type | 值类型
  
  Parameters:
  
  values - the values | 值
  
  keyFunction - the key extractor | 键提取器
  
  Returns:
  
  indexed map | 索引后的 Map
  
  Throws:
  
  OpenCollectionException - if duplicate keys | 如果有重复键
- difference
  
  public static <K,V> MapDifference<K,V> difference(Map<? extends K, ? extends V> left, Map<? extends K, ? extends V> right)
  
  Compute the difference between two maps 计算两个 Map 的差异
  
  Type Parameters:
  
  K - key type | 键类型
  
  V - value type | 值类型
  
  Parameters:
  
  left - left map | 左 Map
  
  right - right map | 右 Map
  
  Returns:
  
  map difference | Map 差异
- transformValues
  
  public static <K,V1,V2> Map<K,V2> transformValues(Map<K,V1> fromMap, Function<? super V1, V2> function)
  
  Return a view with transformed values 转换值视图
  
  Type Parameters:
  
  K - key type | 键类型
  
  V1 - original value type | 原值类型
  
  V2 - transformed value type | 转换后值类型
  
  Parameters:
  
  fromMap - source map | 源 Map
  
  function - transform function | 转换函数
  
  Returns:
  
  transformed view | 转换视图
- transformEntries
  
  public static <K,V1,V2> Map<K,V2> transformEntries(Map<K,V1> fromMap, MapUtil.EntryTransformer<? super K, ? super V1, V2> transformer)
  
  Return a view with transformed entries 转换条目视图
  
  Type Parameters:
  
  K - key type | 键类型
  
  V1 - original value type | 原值类型
  
  V2 - transformed value type | 转换后值类型
  
  Parameters:
  
  fromMap - source map | 源 Map
  
  transformer - entry transformer | 条目转换器
  
  Returns:
  
  transformed view | 转换视图
- filterKeys
  
  public static <K,V> Map<K,V> filterKeys(Map<K,V> unfiltered, Predicate<? super K> keyPredicate)
  
  Return a view filtered by keys 过滤键视图
  
  Type Parameters:
  
  K - key type | 键类型
  
  V - value type | 值类型
  
  Parameters:
  
  unfiltered - source map | 源 Map
  
  keyPredicate - key predicate | 键谓词
  
  Returns:
  
  filtered view | 过滤视图
- filterValues
  
  public static <K,V> Map<K,V> filterValues(Map<K,V> unfiltered, Predicate<? super V> valuePredicate)
  
  Return a view filtered by values 过滤值视图
  
  Type Parameters:
  
  K - key type | 键类型
  
  V - value type | 值类型
  
  Parameters:
  
  unfiltered - source map | 源 Map
  
  valuePredicate - value predicate | 值谓词
  
  Returns:
  
  filtered view | 过滤视图
- filterEntries
  
  public static <K,V> Map<K,V> filterEntries(Map<K,V> unfiltered, Predicate<? super Map.Entry<K,V>> entryPredicate)
  
  Return a view filtered by entries 过滤条目视图
  
  Type Parameters:
  
  K - key type | 键类型
  
  V - value type | 值类型
  
  Parameters:
  
  unfiltered - source map | 源 Map
  
  entryPredicate - entry predicate | 条目谓词
  
  Returns:
  
  filtered view | 过滤视图
- fromProperties
  
  public static Map<String,String> fromProperties(Properties properties)
  
  Create a Properties object to Map 从属性创建 Map
  
  Parameters:
  
  properties - the properties | 属性
  
  Returns:
  
  map | Map
- immutableEntry
  
  public static <K,V> Map.Entry<K,V> immutableEntry(K key, V value)
  
  Create an immutable entry 创建不可变条目
  
  Type Parameters:
  
  K - key type | 键类型
  
  V - value type | 值类型
  
  Parameters:
  
  key - the key | 键
  
  value - the value | 值
  
  Returns:
  
  immutable entry | 不可变条目
- capacity
  
  public static int capacity(int expectedSize)
  
  Calculate capacity for expected size 计算 HashMap 所需容量
  
  Parameters:
  
  expectedSize - expected size | 预期大小
  
  Returns:
  
  capacity | 容量
- synchronizedBiMap
  
  public static <K,V> BiMap<K,V> synchronizedBiMap(BiMap<K,V> bimap)
  
  Create a synchronized BiMap wrapper. 创建同步的 BiMap 包装器。
  
  Type Parameters:
  
  K - key type | 键类型
  
  V - value type | 值类型
  
  Parameters:
  
  bimap - the BiMap to synchronize | 要同步的 BiMap
  
  Returns:
  
  synchronized BiMap | 同步的 BiMap
- unmodifiableBiMap
  
  public static <K,V> BiMap<K,V> unmodifiableBiMap(BiMap<? extends K, ? extends V> bimap)
  
  Create an unmodifiable BiMap wrapper. 创建不可修改的 BiMap 包装器。
  
  Type Parameters:
  
  K - key type | 键类型
  
  V - value type | 值类型
  
  Parameters:
  
  bimap - the BiMap to wrap | 要包装的 BiMap
  
  Returns:
  
  unmodifiable BiMap | 不可修改的 BiMap
- difference
  
  public static <K,V> MapDifference<K,V> difference(Map<? extends K, ? extends V> left, Map<? extends K, ? extends V> right, Equivalence<? super V> valueEquivalence)
  
  Calculate the difference between two maps using custom value equivalence. 使用自定义值等价关系计算两个 Map 的差异。
  
  Type Parameters:
  
  K - key type | 键类型
  
  V - value type | 值类型
  
  Parameters:
  
  left - left map | 左 Map
  
  right - right map | 右 Map
  
  valueEquivalence - value equivalence | 值等价关系
  
  Returns:
  
  map difference | Map 差异

Class MapUtil

Nested Class Summary

Method Summary

Methods inherited from class Object

Method Details

newHashMap

newHashMap

newHashMapWithExpectedSize

newLinkedHashMap

newLinkedHashMapWithExpectedSize

newTreeMap

newTreeMap

newConcurrentMap

newIdentityHashMap

uniqueIndex

uniqueIndex

difference

transformValues

transformEntries

filterKeys

filterValues

filterEntries

fromProperties

immutableEntry

capacity

synchronizedBiMap

unmodifiableBiMap

difference