JAVA9-12新特性簡述

時間 2019-12-14

標籤 java9 java 特性簡述欄目 Java 简体版

原文原文鏈接

本文是我的在企業內部分享使用的簡要大綱，列舉了JAVA9-12的重要更新，文章的結構較簡單，也不規範，鑑於近期寫若干文章時總會忘記一些新特性所處的版本，特將此大綱流copy留用。java

一 JAVA9 新特性shell

1.Java Platform Module System/ Modular Java Application Packaging模塊化系統及類加載器分級編程

2.jshellapi

3.Multi-Release JAR Files 多版本的jar包數組

4.Jlink 工具緩存

5.Segmented Code Cache 代碼片斷緩存併發

6.Dynamic Linking of Language-Defined Object Models 動態連接語言定義模型框架

7.Unified JVM Logging 統一JVM日誌jvm

8.將G1做爲默認垃圾收集器,並deprecated CMS.ide

9.進程API

10.變量句柄

11.字符串內部實現優化(字符數組變字節數組+編碼方式)

12.發佈訂閱框架

13.集合工廠方法

14.自旋暗示

15.對象序列化數據過濾

16."棧旅行者"

17.Milling Project Coin(鬼知道該怎麼翻譯).

Allow @SafeVargs on private instance methods. //容許在私有實例方法上標註@SafeVargs註解

Allow effectively final variables to be used as resources in the try-with-resourcesstatement. //try-with-resource 語法支持實際final的變量

Allow the diamond with anonymous classes if the argument type of the inferred type is denotable.//容許對可推薦出類型的匿名內部類使用鑽石符號.

Complete the removal, begun in Java SE 8, of the underscore from the set of legal identifier names.//移除java8中已經開始的,如下劃線做爲完整標識符名稱

Add support for private interface methods.//接口中可定義私有方法.

18.擴大的unicode集

19.孵化官方http client.

二 JAVA10

1.局部變量類型推斷

2.統必定義的 GC接口.

3.g1垃圾收集器的並行full gc

4.應用類數據共享

5.thread local 握手

6.擴展unicode語言標籤.

三. JAVA11

1.unicode10支持

2.標準化java9中孵化的http客戶端

demo:同步式編程

public void get(String uri) throws Exception {

HttpClient client = HttpClient.newHttpClient();
    HttpRequest request = HttpRequest.newBuilder()
            .uri(URI.create(uri))
            .build();
    HttpResponse<String> response =
            client.send(request, HttpResponse.BodyHandlers.ofString());

    System.out.println(response.body());
}

demo:響應式編程

public CompletableFuture<String> getCompletableFuture(String uri) {

HttpClient client = HttpClient.newHttpClient();
    HttpRequest request = HttpRequest.newBuilder()
            .uri(URI.create(uri))
            .build();

    return client.sendAsync(request, HttpResponse.BodyHandlers.ofString())
            .thenApply(HttpResponse::body);
}

demo:響應式編程-併發

public void testConcurrentRequests(){

HttpClient client = HttpClient.newHttpClient();
    List<String> urls = List.of("http://www.baidu.com","http://www.alibaba.com/","http://www.tencent.com");
    List<HttpRequest> requests = urls.stream()
            .map(url -> HttpRequest.newBuilder(URI.create(url)))
            .map(reqBuilder -> reqBuilder.build())
            .collect(Collectors.toList());

    List<CompletableFuture<HttpResponse<String>>> futures = requests.stream()
            .map(request -> client.sendAsync(request, HttpResponse.BodyHandlers.ofString()))
            .collect(Collectors.toList());
    futures.stream()
            .forEach(e -> e.whenComplete((resp,err) -> {
                if(err != null){
                    err.printStackTrace();
                }else{
                    System.out.println(resp.body());
                    System.out.println(resp.statusCode());
                }
            }));
    CompletableFuture.allOf(futures
            .toArray(CompletableFuture<?>[]::new))
            .join();
}

注：以上代碼是分享時從網上轉來的，由於此文是從內部wiki粘過來，出處已忘。接下來打算髮一篇CompletableFuture有關的文章，最近對響應式編程的興趣更加深入了。

3.Collection.toArray(IntFunction) Default 方法

4.編譯器線程的懶分配

5.體驗版zgc大殺器(缺乏類和元數據卸載)

6.Epsilon GC no-op 體驗版

7.少代價的堆分析工具jvmti

8.nests, an access-control context ,省去編譯器插入accessibility-broadening bridge methods

9.一些屬性變事實的只讀.java.home, user.home, user.dir, user.name等

10.Reference類再也不支持克隆

11.使用classpath進行編譯運行時,默認解析的模塊策略變動:root模塊集在此版本變動爲全部可見的導出api的系統模塊,惟一可見的改變是java.se模塊不在默認解析.

12.SelectableChannel能夠在select操做正在進行中註冊.

13.DatagramChannel.send Throws AlreadyConnectedException Instead of IllegalArgumentException