Don't try to cast metric registry before it is checked for null (#2076)

* Don't try to cast metric registry before it is checked for null

* Simplify the condition check

* Use previously obtained object instead of calling the same getter one more time

---------

Co-authored-by: Alexander Sinuskin <Alexander.Sinuskin.ext@deutsche-boerse.com>

src/main/java/com/zaxxer/hikari/metrics/dropwizard/CodahaleHealthChecker.java

@@ -16,10 +16,6 @@
 
 package com.zaxxer.hikari.metrics.dropwizard;
 
-import java.sql.Connection;
-import java.sql.SQLException;
-import java.util.concurrent.TimeUnit;
-
 import com.codahale.metrics.MetricRegistry;
 import com.codahale.metrics.Timer;
 import com.codahale.metrics.health.HealthCheck;
@@ -27,6 +23,10 @@ import com.codahale.metrics.health.HealthCheckRegistry;
 import com.zaxxer.hikari.HikariConfig;
 import com.zaxxer.hikari.pool.HikariPool;
 
+import java.sql.Connection;
+import java.sql.SQLException;
+import java.util.concurrent.TimeUnit;
+
 /**
  * Provides Dropwizard HealthChecks.  Two health checks are provided:
  * <ul>
@@ -54,13 +54,16 @@ public final class CodahaleHealthChecker
    public static void registerHealthChecks(final HikariPool pool, final HikariConfig hikariConfig, final HealthCheckRegistry registry)
    {
       final var healthCheckProperties = hikariConfig.getHealthCheckProperties();
-      final var metricRegistry = (MetricRegistry) hikariConfig.getMetricRegistry();
 
       final var checkTimeoutMs = Long.parseLong(healthCheckProperties.getProperty("connectivityCheckTimeoutMs", String.valueOf(hikariConfig.getConnectionTimeout())));
       registry.register(MetricRegistry.name(hikariConfig.getPoolName(), "pool", "ConnectivityCheck"), new ConnectivityHealthCheck(pool, checkTimeoutMs));
 
       final var expected99thPercentile = Long.parseLong(healthCheckProperties.getProperty("expected99thPercentileMs", "0"));
-      if (metricRegistry != null && expected99thPercentile > 0) {
+
+      final Object metricRegistryObj = hikariConfig.getMetricRegistry();
+
+      if (expected99thPercentile > 0 && metricRegistryObj instanceof MetricRegistry) {
+         final var metricRegistry = (MetricRegistry) metricRegistryObj;
          var timers = metricRegistry.getTimers((name, metric) -> name.equals(MetricRegistry.name(hikariConfig.getPoolName(), "pool", "Wait")));
 
          if (!timers.isEmpty()) {