Java Tutorials for jdk8复习

Bertha 。 2022-03-22 07:38 124阅读 0赞

1、并发类

*  [`BlockingQueue`][BlockingQueue] defines a first-in-first-out data structure that blocks or times out when you attempt to add to a full queue, or retrieve from an empty queue.

阻塞队列，线程池使用到了

*  [`ConcurrentMap`][ConcurrentMap] is a subinterface of [`java.util.Map`][java.util.Map] that defines useful atomic operations. These operations remove or replace a key-value pair only if the key is present, or add a key-value pair only if the key is absent. Making these operations atomic helps avoid synchronization. The standard general-purpose implementation of `ConcurrentMap` is [`ConcurrentHashMap`][ConcurrentHashMap], which is a concurrent analog of [`HashMap`][HashMap].

HashMap的并发实现[`ConcurrentHashMap`][ConcurrentHashMap],

*  [`ConcurrentNavigableMap`][ConcurrentNavigableMap] is a subinterface of `ConcurrentMap` that supports approximate matches. The standard general-purpose implementation of `ConcurrentNavigableMap` is [`ConcurrentSkipListMap`][ConcurrentSkipListMap], which is a concurrent analog of [`TreeMap`][TreeMap].

TreeMap的并发实现[`ConcurrentSkipListMap`][ConcurrentSkipListMap],

2、集合的算法部分

`Collections` class provides five algorithms for doing routine data manipulation on `List` objects, all of which are pretty straightforward:

*  `reverse` — reverses the order of the elements in a `List`.
 *  `fill` — overwrites every element in a `List` with the specified value. This operation is useful for reinitializing a `List`.
 *  `copy` — takes two arguments, a destination `List` and a source `List`, and copies the elements of the source into the destination, overwriting its contents. The destination `List` must be at least as long as the source. If it is longer, the remaining elements in the destination `List` are unaffected.
 *  `swap` — swaps the elements at the specified positions in a `List`.
 *  `addAll` — adds all the specified elements to a `Collection`. The elements to be added may be specified individually or as an array.

集合提供了针对list的操作，包括reverse、fill、copy、swap和addAll方法

Collections.binarySearch(list, key);

集合类的二分查找

3、集合的聚合操作

roster
        .stream()
        .forEach(e -> System.out.println(e.getName());

double average = roster
        .stream()
        .filter(p -> p.getGender() == Person.Sex.MALE)
        .mapToInt(Person::getAge)
        .average()
        .getAsDouble();

待续

[BlockingQueue]: https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/BlockingQueue.html
[ConcurrentMap]: https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/ConcurrentMap.html
[java.util.Map]: https://docs.oracle.com/javase/8/docs/api/java/util/Map.html
[ConcurrentHashMap]: https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/ConcurrentHashMap.html
[HashMap]: https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html
[ConcurrentNavigableMap]: https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/ConcurrentNavigableMap.html
[ConcurrentSkipListMap]: https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/ConcurrentSkipListMap.html
[TreeMap]: https://docs.oracle.com/javase/8/docs/api/java/util/TreeMap.html