为什么bat脚本的if语句会重复执行，一直打印“找到U盘”

@echo off 

for /f "tokens=2 delims==" %%a in ('wmic logicaldisk where "drivetype='2'" get deviceid /value') do (
	set udisk=%%a 
)
if %udisk% == D: (
    echo 找到U盘
    format D: /fs:fat32 /q /x /y
)else (
    echo 没有找到U盘
)
echo %udisk%
pause