com.sun.management.OperatingSystemMXBean bean = (com.sun.management.OperatingSystemMXBean) java.lang.management.ManagementFactory.getOperatingSystemMXBean();long max = bean.getTotalPhysicalMemorySize();
返回JVM的可用RAM大小(受32位限制),而不是堆大小。

com.sun.management.OperatingSystemMXBean bean = (com.sun.management.OperatingSystemMXBean) java.lang.management.ManagementFactory.getOperatingSystemMXBean();long max = bean.getTotalPhysicalMemorySize();
返回JVM的可用RAM大小(受32位限制),而不是堆大小。