The disposable pattern

Use the disposable pattern along with the try-finally construction to avoid resource leaks.

The disposable pattern is a pattern for resource management. This pattern assumes that an object represents a resource and that the resource can be released by invoking a method such as close or dispose.

The following example demonstrates how to use them:

fun readFirstLine() : String? {
    ......
    var bufferedReader: BufferedReader? = null
    return try {
        ......
        bufferedReader = BufferedReader(inputStreamReader)
        bufferedReader.readLine()
    } catch (e: Exception) {
        null
    } finally {
        ......
        bufferedReader?.close()
    }
}

The Kotlin standard library already has extension functions that use this approach under the hood:

fun readFirstLine(): String? = File("input.txt")
        .inputStream()
        .bufferedReader...