Due to change in JDK-11 and later in ThreadPoolExecutor.java, setMaximumPoolSize needs to be done before setCorePoolSize, the current implementation throws IllegalArgumentException and hence prefilling of connections by setting com.zaxxer.hikari.blockUntilFilled is broken. (#1605)

Co-authored-by: rampr_000 <spachanady@gmail.com>

src/main/java/com/zaxxer/hikari/pool/HikariPool.java

@@ -138,16 +138,16 @@ public final class HikariPool extends PoolBase implements HikariPoolMXBean, IBag
       this.houseKeeperTask = houseKeepingExecutorService.scheduleWithFixedDelay(new HouseKeeper(), 100L, housekeepingPeriodMs, MILLISECONDS);
 
       if (Boolean.getBoolean("com.zaxxer.hikari.blockUntilFilled") && config.getInitializationFailTimeout() > 1) {
-         addConnectionExecutor.setCorePoolSize(Math.min(16, Runtime.getRuntime().availableProcessors()));
          addConnectionExecutor.setMaximumPoolSize(Math.min(16, Runtime.getRuntime().availableProcessors()));
+         addConnectionExecutor.setCorePoolSize(Math.min(16, Runtime.getRuntime().availableProcessors()));
 
          final long startTime = currentTime();
          while (elapsedMillis(startTime) < config.getInitializationFailTimeout() && getTotalConnections() < config.getMinimumIdle()) {
             quietlySleep(MILLISECONDS.toMillis(100));
          }
 
-         addConnectionExecutor.setCorePoolSize(1);
          addConnectionExecutor.setMaximumPoolSize(1);
+         addConnectionExecutor.setCorePoolSize(1);
       }
    }