Java的数据结构相关的类实现

Iterator：

迭代器接口，是Collection接口的父接口。Implementing this interface allows an object to be the target of the "foreach" statement. 也就是说，所有的Collection集合对象都具有foreach可遍历性。

Java 8 新增: forEach() 和 spliterator()

Modifier and Type Method and Description

Modifier and Type	Method and Description
`default void`	`forEach(Consumer<? super T> action)` Performs the given action for each element of the `Iterable` until all elements have been processed or the action throws an exception.
`Iterator<T>`	`iterator()` Returns an iterator over elements of type `T`.
`default Spliterator<T>`	`spliterator()` Creates a `Spliterator` over the elements described by this `Iterable`.

default void

forEach(Consumer<? super T> action)

Performs the given action for each element of the Iterable until all elements have been processed or the action throws an exception.

Iterator<T>

iterator()

Returns an iterator over elements of type T.

default Spliterator<T>

spliterator()

Creates a Spliterator over the elements described by this Iterable.

Collection：

是集合层级结构的根接口。一个collection代表一组object,也称为元素。有些collections允许重复元素，有些不允许。有些collections是有序的，有些是无序的。JDK没有提供这个接口的直接实现，而是提供了一些更具体的子接口，如Set，List。

Java 8 新增：parallelStream()，removeIf(Predicate<? super E> filter)，spliterator()，stream()

Modifier and Type	Method and Description
`boolean`	`add(E e)` Ensures that this collection contains the specified element (optional operation).
`boolean`	`addAll(Collection<? extends E> c)` Adds all of the elements in the specified collection to this collection (optional operation).
`void`	`clear()` Removes all of the elements from this collection (optional operation).
`boolean`	`contains(Object o)` Returns `true` if this collection contains the specified element.
`boolean`	`containsAll(Collection<?> c)` Returns `true` if this collection contains all of the elements in the specified collection.
`boolean`	`equals(Object o)` Compares the specified object with this collection for equality.
`int`	`hashCode()` Returns the hash code value for this collection.
`boolean`	`isEmpty()` Returns `true` if this collection contains no elements.
`Iterator<E>`	`iterator()` Returns an iterator over the elements in this collection.
`default Stream<E>`	`parallelStream()` Returns a possibly parallel `Stream` with this collection as its source.
`boolean`	`remove(Object o)` Removes a single instance of the specified element from this collection, if it is present (optional operation).
`boolean`	`removeAll(Collection<?> c)` Removes all of this collection‘s elements that are also contained in the specified collection (optional operation).
`default boolean`	`removeIf(Predicate<? super E> filter)` Removes all of the elements of this collection that satisfy the given predicate.
`boolean`	`retainAll(Collection<?> c)` Retains only the elements in this collection that are contained in the specified collection (optional operation).
`int`	`size()` Returns the number of elements in this collection.
`default Spliterator<E>`	`spliterator()` Creates a `Spliterator` over the elements in this collection.
`default Stream<E>`	`stream()` Returns a sequential `Stream` with this collection as its source.
`Object[]`	`toArray()` Returns an array containing all of the elements in this collection.
`<T> T[]`	`toArray(T[] a)` Returns an array containing all of the elements in this collection; the runtime type of the returned array is that of the specified array

Map:

Map用于保存键值对，key和value都可以使任何饮用类型的数据。Map的key不允许重复，一个key映射至少一个value。

Map接口提供了三个collections，分别是key set，value collections还有key-value mapping set. Map的顺序就是迭代器迭代出来的顺序。

Java 8 新增：

Modifier and Type Interface and Description

Modifier and Type	Interface and Description
`static interface`	`Map.Entry<K,V>` A map entry (key-value pair).

static interface

Map.Entry<K,V>

A map entry (key-value pair).

Modifier and Type	Method and Description
`void`	`clear()` Removes all of the mappings from this map (optional operation).
`default V`	`compute(K key, BiFunction<? super K,? super V,? extends V> remappingFunction)` Attempts to compute a mapping for the specified key and its current mapped value (or `null` if there is no current mapping).
`default V`	`computeIfAbsent(K key, Function<? super K,? extends V> mappingFunction)` If the specified key is not already associated with a value (or is mapped to `null`), attempts to compute its value using the given mapping function and enters it into this map unless `null`.
`default V`	`computeIfPresent(K key, BiFunction<? super K,? super V,? extends V> remappingFunction)` If the value for the specified key is present and non-null, attempts to compute a new mapping given the key and its current mapped value.
`boolean`	`containsKey(Object key)` Returns `true` if this map contains a mapping for the specified key.
`boolean`	`containsValue(Object value)` Returns `true` if this map maps one or more keys to the specified value.
`Set<Map.Entry<K,V>>`	`entrySet()` Returns a `Set` view of the mappings contained in this map.
`boolean`	`equals(Object o)` Compares the specified object with this map for equality.
`default void`	`forEach(BiConsumer<? super K,? super V> action)` Performs the given action for each entry in this map until all entries have been processed or the action throws an exception.
`V`	`get(Object key)` Returns the value to which the specified key is mapped, or `null` if this map contains no mapping for the key.
`default V`	`getOrDefault(Object key, V defaultValue)` Returns the value to which the specified key is mapped, or `defaultValue` if this map contains no mapping for the key.
`int`	`hashCode()` Returns the hash code value for this map.
`boolean`	`isEmpty()` Returns `true` if this map contains no key-value mappings.
`Set<K>`	`keySet()` Returns a `Set` view of the keys contained in this map.
`default V`	`merge(K key, V value, BiFunction<? super V,? super V,? extends V> remappingFunction)` If the specified key is not already associated with a value or is associated with null, associates it with the given non-null value.
`V`	`put(K key, V value)` Associates the specified value with the specified key in this map (optional operation).
`void`	`putAll(Map<? extends K,? extends V> m)` Copies all of the mappings from the specified map to this map (optional operation).
`default V`	`putIfAbsent(K key, V value)` If the specified key is not already associated with a value (or is mapped to `null`) associates it with the given value and returns `null`, else returns the current value.
`V`	`remove(Object key)` Removes the mapping for a key from this map if it is present (optional operation).
`default boolean`	`remove(Object key, Object value)` Removes the entry for the specified key only if it is currently mapped to the specified value.
`default V`	`replace(K key, V value)` Replaces the entry for the specified key only if it is currently mapped to some value.
`default boolean`	`replace(K key, V oldValue, V newValue)` Replaces the entry for the specified key only if currently mapped to the specified value.
`default void`	`replaceAll(BiFunction<? super K,? super V,? extends V> function)` Replaces each entry‘s value with the result of invoking the given function on that entry until all entries have been processed or the function throws an exception.
`int`	`size()` Returns the number of key-value mappings in this map.
`Collection<V>`	`values()` Returns a `Collection` view of the values contained in this map.

时间： 2024-08-11 06:03:14

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