import java.io.*;
import com.sun.management.OperatingSystemMXBean;
import sun.management.ManagementFactory;
public class Tst{
    public static String pt="D:\\abc.txt";
    public Tst(){
    }
    public static void main(String[] args) throws Exception{
        //free和use和total均为KB
        long free=0;
        long use=0;
        long total=0;
        int kb=1024;
        Runtime rt=Runtime.getRuntime();
        total=rt.totalMemory();
        free=rt.freeMemory();
        use=total-free;
        System.out.println("系统内存已用的空间为："+use/kb+" MB");
        System.out.println("系统内存的空闲空间为："+free/kb+" MB");
        System.out.println("系统总内存空间为："+total/kb+" MB");
        OperatingSystemMXBean osmxb = (OperatingSystemMXBean) ManagementFactory.getOperatingSystemMXBean();
        long physicalFree=osmxb.getFreePhysicalMemorySize()/kb;
        long physicalTotal=osmxb.getTotalPhysicalMemorySize()/kb;
        long physicalUse=physicalTotal-physicalFree;
        String os=System.getProperty("os.name");
        System.out.println("操作系统的版本："+os);
        System.out.println("系统物理内存已用的空间为："+physicalFree+" MB");
        System.out.println("系统物理内存的空闲空间为："+physicalUse+" MB");
        System.out.println("总物理内存："+physicalTotal+" MB");
        // 获得线程总数
        ThreadGroup parentThread;
        for (parentThread = Thread.currentThread().getThreadGroup(); parentThread
                .getParent() != null; parentThread = parentThread.getParent())
            ;
        int totalThread = parentThread.activeCount();
        System.out.println("获得线程总数:"+totalThread);
    }    
}