Evergreen Java

Memory Layout of Objects in Java

Compressed OOPs in the JVM

https://www.baeldung.com/jvm-compressed-oops

How To Install

brew tap AdoptOpenJDK/openjdk
brew cask install <version>

https://github.com/AdoptOpenJDK/homebrew-openjdk

java15

ZGC

https://www.baeldung.com/jvm-zgc-garbage-collector

java13

study

Switch Expression

https://blog.naver.com/gngh0101/221945983737

Reference

https://blog.codefx.org/java/java-13-guide/

java11

study

Time

ZoneDateTime

LocalDateTime + Time-Zone

Instant

에포크 타임(EPOCH TIME, 1970-01-01 00:00:00 UTC)부터 경과된 시간을 나노초 단위로 표현한다

OffSet

UTC로 부터 얼마만큼 떨어져 있는지

String

strip

공백 제거 메서드, 유니코드도 제거해준다.

isBlank

공백 체크 메서드, 유니코드도 체크해준다.

lines

\n 라인 별로 잘라준다.

repeat

문자열을 반복한다.

HttpClient

자바11에 추가된 Client 라이브러리

block

  @Test
  public void httpClient_block() throws IOException, InterruptedException {
    final HttpClient httpClient = HttpClient.newHttpClient();
    final HttpRequest httpRequest = HttpRequest.newBuilder().uri(URI.create(JAVA11_URL)).GET().build();
    final HttpResponse<String> httpResponse = httpClient.send(httpRequest, HttpResponse.BodyHandlers.ofString());
    assertEquals(httpResponse.body(), "hello");
  }

async

 @Test
  public void httpClient_async() throws IOException, InterruptedException {
    final HttpClient httpClient = HttpClient.newHttpClient();
    final HttpRequest httpRequest = HttpRequest.newBuilder().uri(URI.create(JAVA11_URL)).GET().build();
    CompletableFuture<HttpResponse<String>> future = httpClient.sendAsync(httpRequest, BodyHandlers.ofString());
    future.thenApply(HttpResponse::body)
      .thenAccept(log::info);

    log.info("async");
    Thread.sleep(1000); // shutdown
  }

: 그냥 WebClient 쓰자.

Compact String

vm option (default)

-XX:+UseCompressedStrings

char[] 가 아닌 byte[]

public final class String
    implements java.io.Serializable, Comparable<String>, CharSequence {

    @Stable
    private final byte[] value;
}

How It Works

 private final byte coder;

: LATIN1 / UTF16을 구별하는 필드

public int indexOf(String str) {
        if (coder() == str.coder()) {
            return isLatin1() ? StringLatin1.indexOf(value, str.value)
                              : StringUTF16.indexOf(value, str.value);
        }
        if (coder() == LATIN1) {  // str.coder == UTF16
            return -1;
        }
        return StringUTF16.indexOfLatin1(value, str.value);
    }

: isLatin1() 체크를 통해 StringLantin1 / StringUTF16 으로 나누어 처리한다.

Performance Test

: CompactPerformanceTest.class

baeldung-java-tutorial

https://www.baeldung.com/java-tutorial

Native

https://www.baeldung.com/java-native

Beyond Java

https://blog.naver.com/gngh0101/222396980468

withbeth/evergreen-java