获取内存空间大小

    //总内存
    long   totalMemory=Runtime.getRuntime().totalMemory();

    //占用内存
    long freeMemory=Runtime.getRuntime().freeMemory();
    System.out.println("总内存:"+totalMemory);
    System.out.println("内存使用:"+freeMemory);
    for(int i=0;i<1000000;i++){
       List list=new ArrayList();
    }

    //占用内存
    long NewFreeMemory=Runtime.getRuntime().freeMemory();
    long NewTotalMemory=Runtime.getRuntime().totalMemory();
    System.out.println("总内存:"+NewTotalMemory);
    System.out.println("内存使用:"+NewFreeMemory);
       for(int i=0;i<1000000;i++){
       List list=null;
    }

    //占用内存
    long NewFreeMemorys=Runtime.getRuntime().freeMemory();
    long NewTotalMemorys=Runtime.getRuntime().totalMemory();
    System.out.println("总内存:"+NewTotalMemorys);
    System.out.println("内存使用:"+NewFreeMemorys);