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How to filter lines in a file based on a condition in Kotlin

How to filter lines in a file based on a condition in Kotlin.

Here's a step-by-step tutorial on how to filter lines in a file based on a condition in Kotlin:

Step 1: Create a new Kotlin project and add a file to read from​

  • Start by creating a new Kotlin project in your preferred IDE.
  • Create a text file that contains the lines you want to filter. Name it, for example, "input.txt".
  • Populate the file with some sample lines that you will filter based on a condition.

Step 2: Read the lines from the file​

  • In your Kotlin code, import the necessary classes for file handling:

    import java.io.File

  • Use the readLines() function provided by the File class to read the lines from the file:

    val lines = File("input.txt").readLines()

Step 3: Define the condition for filtering the lines​

  • Determine the condition based on which you want to filter the lines.
  • For example, let's say you want to filter out all lines that contain the word "example". You can define a condition like this:
    val condition: (String) -> Boolean = { line -> !line.contains("example") }

Step 4: Filter the lines based on the condition​

  • Use the filter() function provided by the Kotlin standard library to filter the lines based on the defined condition:
    val filteredLines = lines.filter(condition)

Step 5: Print or use the filtered lines​

  • You can now choose what to do with the filtered lines.
  • For example, let's print each filtered line:
    filteredLines.forEach { line ->
        println(line)
    }

Step 6: Run the program and observe the filtered lines​

  • Run your Kotlin program and observe the output.
  • You should see only the lines that satisfy the defined condition printed or used accordingly.

That's it! You have successfully filtered lines in a file based on a condition in Kotlin. You can customize the condition to suit your specific needs, such as filtering lines that match a regular expression, contain specific characters, or have certain patterns.