import sun.jvm.hotspot.memory.Universe; //导入依赖的package包/类
public void doit(Tokens t) {
    if (t.countTokens() != 0) {
        usage();
    } else {
        Universe u = VM.getVM().getUniverse();
        out.println("Heap Parameters:");
        u.heap().printOn(out);
    }
}
 

import sun.jvm.hotspot.memory.Universe; //导入依赖的package包/类
private Universe getUniverse() {
    return vm.saUniverse();
}
 

import sun.jvm.hotspot.memory.Universe; //导入依赖的package包/类
Universe saUniverse() {
    return saUniverse;
}
 

import sun.jvm.hotspot.memory.Universe; //导入依赖的package包/类
@Override
public HotSpotSACompressedReferencesResult run(HotSpotServiceabilityAgentContext context,
                                               NoHotSpotServiceabilityAgentParameter param) {
    try {
        Class<?> universeClass = HotSpotServiceabilityAgentUtil.getUniverseClass();
        Class<?> vmClass = HotSpotServiceabilityAgentUtil.getVmClass();
        VM vm = HotSpotServiceabilityAgentUtil.getVMInstance();

        Method getKlassOopSizeMethod = null;
        Method isCompressedKlassOopsEnabledMethod = null;
        Method getNarrowKlassBaseMethod = null;
        Method getNarrowKlassShiftMethod = null;

        try {
            getKlassOopSizeMethod = vmClass.getMethod("getKlassPtrSize");
            isCompressedKlassOopsEnabledMethod = vmClass.getMethod("isCompressedKlassPointersEnabled");
            getNarrowKlassBaseMethod = universeClass.getMethod("getNarrowKlassBase");
            getNarrowKlassShiftMethod = universeClass.getMethod("getNarrowKlassShift");
        } catch (NoSuchMethodException e) {
            // There is nothing to do, seems target JVM is not Java 8
        }

        int addressSize = (int) vm.getOopSize();
        int objectAlignment = vm.getObjectAlignmentInBytes();

        int oopSize = vm.getHeapOopSize();
        boolean compressedOopsEnabled = vm.isCompressedOopsEnabled();
        long narrowOopBase = Universe.getNarrowOopBase();
        int narrowOopShift = Universe.getNarrowOopShift();

        /*
         * If compressed klass references is not supported (before Java 8),
         * use compressed oop references values instead of them.
         */

        int klassOopSize = getKlassOopSizeMethod != null ? 
                (Integer) getKlassOopSizeMethod.invoke(vm) : oopSize;
        boolean compressedKlassOopsEnabled = isCompressedKlassOopsEnabledMethod != null ? 
                (Boolean) isCompressedKlassOopsEnabledMethod.invoke(vm) : compressedOopsEnabled;
        long narrowKlassBase = getNarrowKlassBaseMethod != null ? 
                (Long) getNarrowKlassBaseMethod.invoke(null) : narrowOopBase;
        int narrowKlassShift = getNarrowKlassShiftMethod != null ? 
                (Integer) getNarrowKlassShiftMethod.invoke(null) : narrowOopShift;

        return new HotSpotSACompressedReferencesResult(addressSize, objectAlignment, 
                oopSize, compressedOopsEnabled, narrowOopBase, narrowOopShift, 
                klassOopSize, compressedKlassOopsEnabled, narrowKlassBase, narrowKlassShift);
    } catch (Throwable t) {
        throw new RuntimeException(t.getMessage(), t);
    }
}