Why does postContruct() get called twice...

DropWizardMetricSets.java

package com.foo.server;

import com.codahale.metrics.MetricRegistry;
import com.codahale.metrics.jvm.GarbageCollectorMetricSet;
import com.codahale.metrics.jvm.MemoryUsageGaugeSet;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.Configuration;

import javax.annotation.PostConstruct;

/**
 * Configurable use of `metrics-jvm` from DropWizard - collects garbage collection and memory usage by default.
 *
 * See also http://stackoverflow.com/questions/32215723/exporting-spring-boot-actuator-metrics-dropwizard-metrics-to-statsd
 * Created by jgreen on 05/10/2016.
 */
@Configuration
@ConfigurationProperties(prefix = "dropwizard")
public class DropWizardMetricSets {
    @Autowired
    private MetricRegistry metricRegistry;

    private boolean garbageCollectorReporting = false;
    private boolean memoryUsageReporting = false;

    public void setGarbageCollectorReporting(boolean garbageCollectorReporting) {
        this.garbageCollectorReporting = garbageCollectorReporting;
    }

    public void setMemoryUsageReporting(boolean memoryUsageReporting) {
        this.memoryUsageReporting = memoryUsageReporting;
    }

    @PostConstruct
    public void postConstruct() {
        if (garbageCollectorReporting) {
            metricRegistry.register("jvm.gc", new GarbageCollectorMetricSet());
        }
        if (memoryUsageReporting) {
            metricRegistry.register("jvm.mem", new MemoryUsageGaugeSet());
        }
    }
}