计算传入文件的大小

/**
* 传入文件大小，返回 KB MB GB 
* 如: 传入10240 返回10.0 KB
* @param fileSize
* 文件大小
* @return 文件大小
*/
public static String getFileSize(long fileSize) {

String size = "";
if (fileSize < 1024) {
size = fileSize + "B";
}else if (fileSize < 1024 * 1024) {
size = fileSize / 1024 + "." + (fileSize % 1024 * 10) / 1024 + "KB";
}else if (fileSize < 1024 * 1024 * 1024) {
size = fileSize / (1024 * 1024) + "." + (fileSize % (1024 * 1024)) * 10 / (1024 * 1024) + "MB";
}else if (fileSize < 1024 * 1024 * 1024 * 1024) {
size = fileSize / (1024 * 1024 * 1024) + "." + (fileSize % (1024 * 1024 * 1024)) * 10 / (1024 * 1024 * 1024) + "GB";
}
return size;
}