Java 11 HttpClient

Connection Pool

Keep Alive Timeout : System Property jdk.httpclient.keepalive.timeout=1200 (초단위) 로 지정.
Connection Pool Max Size : System Property jdk.httpclient.connectionPoolSize=0 0이면 무제한. 갯수로 지정.
http2 - How to keep connection alive in Java 11 http client - Stack Overflow
openjdk-jdk11/ConnectionPool.java at master · AdoptOpenJDK/openjdk-jdk11

HttpClient.newBuilder()
      .proxy(ProxySelector.getDefault())
      .build();

HttpClient client = HttpClient.newBuilder()
      .proxy(ProxySelector.of(new InetSocketAddress("www-proxy.com", 8080)))
      .build();