检查 字节流的大小

public static String sizeFormat(long dataSize){
		if(dataSize>=1073741824){
			return ((double) Math.round(dataSize / 1073741824d * 100) / 100)+ " GB";
		}else if(dataSize>=1048576){
			return ((double) Math.round(dataSize / 1048576d * 100) / 100)+ " MB";
		}else if(dataSize>=1024){
			return ((double) Math.round(dataSize / 1024d * 100) / 100)+ " KB";
		}else{
			return dataSize+ " Bytes";
		}
	}