Kotlin – How to read File with Kotlin language

This tutorial shows you how to read File in Kotlin using InputStream or BufferedReader.

I. Technology

– Java 1.8
– Kotlin 1.1.2

II. Overview

1. Goal

Read file: all lines/by line using InputStream or BufferedReader or File directly.

2. Steps to do

– Create:
+ InputStream from File, then get BufferedReader using bufferedReader() method
+ BufferedReader from File.
– Use:
+ Closeable.use() method with Reader.readText() method inside block. Closeable.use() will automatically close the input at the end of the lambda’s execution:

+ Reader.useLines() method with Kotlin Sequence (a sequence of all the lines) inside block. Reader.useLines() will automatically close the reader once the processing is complete:

+ File.useLines() method with Kotlin Sequence (a sequence of all the lines) inside block. It will close the reader once the processing is complete:

+ File.readLines() method to return a List<String>:

III. Practice

0. kotli.txt

1. Use InputStream
1.1 Read All Lines

Check Result:

1.2 Read By Line

Check Result:

2. Use BufferedReader
2.1 Read All Lines

Check Result:

2.2 Read By Line

Check Result:

3. Use File directly

Check Result:

By JavaSampleApproach | August 29, 2017.


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