C:\Users\user>cd C:/Temp/

C:\Temp>dir
 C 드라이브의 볼륨: 메인
 볼륨 일련 번호: 7040-99CF

 C:\Temp 디렉터리

2020-02-02  오전 10:06    DIR            .
2020-02-02  오전 10:06    DIR            ..
2019-11-09  오후 12:51    DIR            AUtempR
2020-01-26  오전 07:38           112,526 CPU_RANK.txt
2020-01-26  오전 09:13             1,378 KBS_20200201_1234.txt
2018-05-22  오전 12:23           521,727 SC20120709-103828.png
2018-11-07  오후 09:00                68 test.json
2019-09-18  오후 08:32            48,562 workbook.xlsx
C:\Temp>

-- ^^

File path = new File("C:/Temp/");
String fileList[] = path.list((dir, name) -> name.endsWith("txt"));

for (String fileName : fileList) {
    System.out.println("--------->> " + fileName);
}

-- ^^

Result(결과)
--------->> CPU_RANK.txt
--------->> KBS_20200201_1234.txt