import sun.management.GcInfoBuilder; //导入依赖的package包/类
private GcInfo(GcInfoBuilder builder,
               long index, long startTime, long endTime,
               MemoryUsage[] muBeforeGc,
               MemoryUsage[] muAfterGc,
               Object[] extAttributes) {
    this.builder       = builder;
    this.index         = index;
    this.startTime     = startTime;
    this.endTime       = endTime;
    String[] poolNames = builder.getPoolNames();
    this.usageBeforeGc = new HashMap<String, MemoryUsage>(poolNames.length);
    this.usageAfterGc = new HashMap<String, MemoryUsage>(poolNames.length);
    for (int i = 0; i < poolNames.length; i++) {
        this.usageBeforeGc.put(poolNames[i],  muBeforeGc[i]);
        this.usageAfterGc.put(poolNames[i],  muAfterGc[i]);
    }
    this.extAttributes = extAttributes;
    this.cdata = new GcInfoCompositeData(this, builder, extAttributes);
}