31  */
  32 public enum GC {
  33     /*
  34      * Enum values must match CollectedHeap::Name
  35      */
  36     Serial(1),
  37     Parallel(2),
  38     G1(3),
  39     Epsilon(4),
  40     Z(5),
  41     Shenandoah(6);
  42 
  43     private static final WhiteBox WB = WhiteBox.getWhiteBox();
  44 
  45     private final int name;
  46 
  47     private GC(int name) {
  48         this.name = name;
  49     }
  50 
  51     private boolean supportsOSVersion() {
  52         if (this != Z) {
  53             return true;
  54         }
  55 
  56         String osName = System.getProperty("os.name");
  57 
  58         if (!osName.startsWith("Windows")) {
  59             return true;
  60         }
  61 
  62         // ZGC has specific Windows version requirements (>= 1803).
  63         // The following check should be made more precise to
  64         // also catch the corresponding Windows 10 version.
  65         return osName.equals("Windows Server 2019");
  66     }
  67 
  68     /**
  69      * @return true if this GC is supported by the VM, i.e., it is built into the VM.
  70      */
  71     public boolean isSupported() {
  72         return WB.isGCSupported(name) && supportsOSVersion();
  73     }
  74 
  75     /**
  76      * @return true if this GC is currently selected/used
  77      */
  78     public boolean isSelected() {
  79         return WB.isGCSelected(name);
  80     }
  81 
  82     /**
  83      * @return true if GC was selected ergonomically, as opposed
  84      *         to being explicitly specified on the command line
  85      */
  86     public static boolean isSelectedErgonomically() {
  87         return WB.isGCSelectedErgonomically();
  88     }
  89 
  90     /**
  91      * @return the selected GC.
  92      */

  31  */
  32 public enum GC {
  33     /*
  34      * Enum values must match CollectedHeap::Name
  35      */
  36     Serial(1),
  37     Parallel(2),
  38     G1(3),
  39     Epsilon(4),
  40     Z(5),
  41     Shenandoah(6);
  42 
  43     private static final WhiteBox WB = WhiteBox.getWhiteBox();
  44 
  45     private final int name;
  46 
  47     private GC(int name) {
  48         this.name = name;
  49     }
  50 

















  51     /**
  52      * @return true if this GC is supported by the VM, i.e., it is built into the VM.
  53      */
  54     public boolean isSupported() {
  55         return WB.isGCSupported(name);
  56     }
  57 
  58     /**
  59      * @return true if this GC is currently selected/used
  60      */
  61     public boolean isSelected() {
  62         return WB.isGCSelected(name);
  63     }
  64 
  65     /**
  66      * @return true if GC was selected ergonomically, as opposed
  67      *         to being explicitly specified on the command line
  68      */
  69     public static boolean isSelectedErgonomically() {
  70         return WB.isGCSelectedErgonomically();
  71     }
  72 
  73     /**
  74      * @return the selected GC.
  75      */