JDK19都出来了~是时候梳理清楚JDK的各个版本的特性了【JDK11特性讲解】

Consumer<String> con =(@Deprecated  t) -> System.out.println(t.toLowerCase());

Consumer<String> con =(@Deprecated String t) -> System.out.println(t.toLowerCase());

Consumer<String> con =(@Deprecated var t) -> System.out.println(t.toLowerCase());

    public static void main(String[] args) {
        // 判断字符串是否为空白
        boolean b = " ".isBlank();// true
        // 去除字符串首尾空白
        String s1 = " www.boge.com ".strip();// "www.boge.com"
        // 去除字符串尾部空格
        String s2 = " www.boge.com ".stripTrailing();// " \n \twww.boge.com"
        // 去除字符串首部空格
        String s3 = " www.boge.com ".stripLeading();// "www.boge.com\n \t "
        // 复制字符串
        String r = "boge".repeat(2);// "bogeboge"
        // 行数统计
        long c = "A\nB\nC\nD".lines().count();// 4
        System.out.println(s1);
        System.out.println(s2);
        System.out.println(s3);
        System.out.println(r);
        System.out.println(c);
    }

    public static void main(String[] args) {
        Optional<String> optional =Optional.empty();
        //JDK8 判断value是否存在
        System.out.println(optional.isPresent());
        //JDK11 判断value是否为空
        System.out.println(optional.isEmpty());

        //JDK10 返回value,如果为null则直接抛出 NoSuchElementExpception
        Optional<String> optional2 = Optional.of("element1");
        String value = optional2.orElseThrow();
        System.out.println(value);

        //JDK9  value非空,执行参数1功能,如果value为空,执行参数2功能
        Optional<String> optional3 =Optional.empty();// Optional.of("element1");
        optional.ifPresentOrElse((v)-> System.out.println("value为"+v),()-> System.out.println("value为null"));

        // JDK9 value非空,返回对应的Optional,value为空,返回形参封装的Optional
        Optional<String> optional4 =Optional.empty();// Optional.of("element1");
        Optional<String> optional5 = optional4.or(() -> Optional.of("element2"));
        System.out.println(optional5);

        // JDK9 value非空,返回一个仅包含此value的Steam,否则,返回一个空的Stream
        Optional<String> optional6 =Optional.of("element3");//Optional.empty();
        Stream<String> stream = optional6.stream();
        stream.forEach(System.out::println);
    }

//HttpClient 替换原有的HttpUrlConnection  同步方式
HttpClient client =HttpClient.newHttpClient();
HttpRequest request =HttpRequest.newBuilder(URI.create("http://127.0.0.1:8080/demo")).build();
HttpResponse.BodyHandler<String> respnoseBodyHandler= HttpResponse.BodyHandlers.ofString();
HttpResponse<String> response =client.send(request,respnoseBodyHandler);
String body = response.body();
System.out.println(body);

//HttpClient 替换原有的HttpUrlConnection  异步方式
HttpClient client =HttpClient.newHttpClient();
HttpRequest request =HttpRequest.newBuilder(URI.create("http://127.0.0.1:8080/demo")).build();
HttpResponse.BodyHandler<String> respnoseBodyHandler= HttpResponse.BodyHandlers.ofString();
CompletableFuture<HttpResponse<String>> sendAsync = client.sendAsync(request, respnoseBodyHandler);
sendAsync.thenApply(t-> t.body()).thenAccept(System.out::println);

javac Test1.java

java Test1

java Test1.java

public class HelloJAVA11{
    public static void main(String[] args){
        System.out.println("HelloJAVA11.main");
        // 实例化当前文件中的Person类
        Person p=new Person();
        // 实例化另一个文件中的Student类
        Student stu =new Student();
  
    }
  
}

class Person {
    private String pid;
    private String pname;
  
}
class Test2{
    public static void main(String[] args){
        System.out.println("Test2.main");
    }
}

public class Student{
  
}