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3-11 JDK11 其他新特性

3-10 JDK11 中新增加的常用 API

import?org.jetbrains.annotations.NotNull;

import?java.util.ArrayList;
import?java.util.Arrays;
import?java.util.List;
import?java.util.Map;

public?class?LocalVarExample?{

????/**
?????*?java8特性：lambda表達式語法
?????*/
????public?static?void?lambdaInJava8()?{
????????new?Thread(new?Runnable()?{
????????????@Override
????????????public?void?run()?{
????????????????System.out.println("before?java8");
????????????}
????????}).start();

????????new?Thread(()->?System.out.println("in?java8")).start();
????????List<String>?list?=?Arrays.asList("java8","jdk8","1.8");
????????list.forEach(w->{
????????????System.out.println("lambda?in?java8->"+w);
????????});
????}

????/**
?????*Java10?新特性：局部變量類型推斷
?????*/
????private?static?void?varInJava10(){
????????int?var?=10;
????????var?i?=10;
????????var?str?=?"java10";
????????var?list?=?new?ArrayList<String>();
????????var?map?=?Map.of(1,"a",2,"b");
????????for(var?entry?:?map.entrySet()){
????????????System.out.println(entry);
????????}
????}

????/**
?????*Java11?新特性：允許var在聲明隱式類型的lambda表達式的形式參數時使用
?????*/
????private?static?void?lambdaWithVarInJava11?(){
???????List<Integer>?nums?=?Arrays.asList(9,11,23,3,7,2,8);
//???????nums.sort((s1,s2)->{
//???????????if(s1.equals(s2)){
//???????????????return?0;
//???????????}else{
//???????????????return?s1?>?s2???1:-1;
//???????????}
//???????});
???????nums.sort((@NotNull?var?s1,?@NotNull?var?s2)->{
???????????if?(s1.equals(s2))?{
???????????????return?0;
???????????}?else?{
???????????????return?s1?>?s2???1?:?-1;
???????????}
???????});
???????nums.sort((s1,s2)->?s1?>?s2???1:-1);
???????System.out.println(nums);
????}

????/**
?????*?Lambda參數的本地變量語法
?????*/
????public?static?void?main(String[]?args)?{
//????????lambdaInJava8();
//????????varInJava10();
????????lambdaWithVarInJava11();
????}
}

import?java.net.URI;
import?java.net.http.HttpClient;
import?java.net.http.HttpRequest;
import?java.net.http.HttpResponse;
import?java.util.concurrent.CompletableFuture;

/**
?*?標準HTTP客戶端
?*/
public?class?HttpClientExample?{
????/**
?????*?同步Get方法
?????*?@param?uri
?????*?@throws?Exception
?????*/
????private?static?void?synGet(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.statusCode());
????????System.out.println(response.body());
????}

????/**
?????*?異步Get方法
?????*?@param?uri
?????*?@throws?Exception
?????*/
????private?static?void?asyncGet(String?uri)?throws?Exception?{
????????HttpClient?client?=?HttpClient.newHttpClient();
????????HttpRequest?request?=?HttpRequest.newBuilder().uri(
????????????????URI.create(uri)).build();
????????CompletableFuture<HttpResponse<String>>?future?=?client.sendAsync(request,HttpResponse.BodyHandlers.ofString());
????????future.whenComplete((resp,ex)->{
????????????if?(ex!=null){
????????????????ex.printStackTrace();
????????????}else?{
????????????????System.out.println(resp.statusCode());
????????????????System.out.println(resp.body());
????????????}
????????}).join();
????}

????public?static?void?main(String[]?args)?throws?Exception?{
????????String?uri?=?"http://t.weather.sojson.com/api/weather/city/101030100";
????????//synGet(uri);
????????asyncGet(uri);
????}
}

import?java.util.concurrent.TimeUnit;

/**
?*?改進Aarch64函數
?*/
public?class?Aarch64Example?{
????public?static?void?mathOnJdk11()?{
????????long?startTime?=?System.nanoTime();
????????for?(int?i?=?0;?i?<?100000000;?i++)?{
????????????Math.sin(i);
????????????Math.cos(i);
????????????Math.log(i);
????????}
????????long?endTime?=?System.nanoTime();
????????System.out.println(TimeUnit.NANOSECONDS.toMillis(endTime-startTime)+"ms");
????}

????public?static?void?main(String[]?args)?{
????????mathOnJdk11();
????}
}

import?java.lang.invoke.MethodHandle;
import?java.lang.invoke.MethodHandles;
import?java.lang.invoke.MethodType;

/**
?*?動態語言API測試
?*/
public?class?DynamicTest?{
????private?static?void?test(){
????????System.out.println("動態語言API測試");
????}
????public?static?void?main(String[]?args)?throws?Throwable?{
????????//?public方法的Lookup
//????????MethodHandles.Lookup?publicLookup?=?MethodHandles.publicLookup();
????????//?所有方法的Lookup
????????MethodHandles.Lookup?lookup?=?MethodHandles.lookup();
????????MethodHandle?mh?=?lookup.findStatic(DynamicTest.class,"test",?MethodType.methodType(void.class));
????????mh.invokeExact();
????}
}

動態語言API測試

G1垃圾收集器會將堆內存分配為等大小的region默認情況下是2048個region

對象內存分配過快，mixed gc來不及清理，導致old region被沾滿會觸發full gc，full gc是單線程執行

老年代占用的內存大小超過堆內存的預值時會觸發mixed gc,預值可以在啟動的時候指定

G1垃圾收集器

并發表及掃描垃圾回收器

并行垃圾收集器

串行垃圾收集器