code: public static int xmx2MB(String xmx) {
          int size = 200;
          if (xmx == null || xmx.isEmpty()) {
              return size;
          }
  
          String s = xmx.substring(xmx.length() - 1, xmx.length());
          int unit = -1;
          int localSize = -1;
          if (unitMap.get(s) == null) {
              localSize = Integer.valueOf(xmx.substring(4, xmx.length()));
              return localSize / 1024 / 1024;
          } else {
              unit = unitMap.get(s);
              localSize = Integer.valueOf(xmx.substring(4, xmx.length() - 1));
          }
  
          switch (unit) {
          case K:
              size = localSize / 1024;
              break;
          case M:
              size = localSize;
              break;
          case G:
              size = localSize * 1024;
              break;
          }
  
          return size;
      }
docs: -Xmx to MByte
  @param xmx
  @return MByte