Question

I have a text file just like below

add device 1: /dev/input/event7
  name:     "evfwd"
add device 2: /dev/input/event6
  name:     "aev_abs"
add device 3: /dev/input/event5
  name:     "light-prox"
add device 4: /dev/input/event4
  name:     "qtouch-touchscreen"
add device 5: /dev/input/event2
  name:     "cpcap-key"
add device 6: /dev/input/event1
  name:     "accelerometer"
add device 7: /dev/input/event0
  name:     "compass"
add device 8: /dev/input/event3
  name:     "omap-keypad"
4026-275085: /dev/input/event5: 0011 0008 0000001f
4026-275146: /dev/input/event5: 0000 0000 00000000
4026-494201: /dev/input/event5: 0011 0008 00000020
4026-494354: /dev/input/event5: 0000 0000 00000000

what i need to do is i want to remove the add device preambles, i just need the lines starting from 4026-275…
that is,

    4026-275085: /dev/input/event5: 0011 0008 0000001f
    4026-275146: /dev/input/event5: 0000 0000 00000000
    4026-494201: /dev/input/event5: 0011 0008 00000020
    4026-494354: /dev/input/event5: 0000 0000 00000000

now this numbers can vary. How can I extract this efficiently. the preambles line numbers are not constant.

Answer 1

Just keep only the lines beginning with a digit.

for (String line : lines) {
    if (line.matches("^\\d+.*")) {
        System.out.println("line starts with a digit");
    }
}