HotSpot VM utils

GCUtils.java

public class GCUtils {
  private static final String DISABLE_EXPLICIT_GC = "DisableExplicitGC"; // need to be "manageable" in VM
  
  public static void forceGC() {
    String oldValue = HotSpotUtils.getVMOption(DISABLE_EXPLICIT_GC);
    if ("true".equals(oldValue)) {
      HotSpotUtils.setVMOption(DISABLE_EXPLICIT_GC, "false");
      System.gc();
      HotSpotUtils.setVMOption(DISABLE_EXPLICIT_GC, oldValue);
    } else {
      System.gc();
    }
  }
}

HotSpotUtils.java

import java.lang.management.ManagementFactory;
import javax.management.MBeanServer;
import com.sun.management.HotSpotDiagnosticMXBean;
// import com.sun.management.VMOption;

public class HotSpotUtils {
  public static String getVMOption(String name) {
    return SingletonHolder.HOTSPOT_BEAN.getVMOption(name).getValue(); // could throw exception
  }
  
  public static void setVMOption(String name, String value) {
    SingletonHolder.HOTSPOT_BEAN.setVMOption(name, value);
  }
  
  private static class SingletonHolder {
    static final HotSpotDiagnosticMXBean HOTSPOT_BEAN = populateHotSpotBean();
    private static final String HOTSPOT_BEAN_NAME = "com.sun.management:type=HotSpotDiagnostic";
    
    private static final HotSpotDiagnosticMXBean populateHotSpotBean() {
      try {
        MBeanServer server = ManagementFactory.getPlatformMBeanServer();
        HotSpotDiagnosticMXBean bean = ManagementFactory.newPlatformMXBeanProxy(
          server, HOTSPOT_BEAN_NAME, HotSpotDiagnosticMXBean.class);
        return bean;
      } catch (java.io.IOException e) {
        throw new InternalError("should run on a HotSpot VM");
      }
    }
  }
}