Read a Text File

Top Ten Tips

Hello World

Convert to Number

Read Text File

Sum an Array

Count 0 to 9

Hash Table

Regular Expression

Read Database

Read XML

Define a Class

You can open a text file and read each line.

• The BufferedReader represents a text file.
• You can create BufferedReader from an

FileReader.

• The while condition (s=fh.readLine())!=null does two

things, it assigns the string s and it checks for null.

The text file [haggis.txt] includes some lines of text.

.

import java.io.BufferedReader; import java.io.FileReader; public class Demo{ public static void main(String[] argv) throws Exception{ BufferedReader fh = new BufferedReader(new FileReader("haggis.txt")); String s; while ((s=fh.readLine())!=null) System.out.println(s); fh.close(); } }

[Font] [Default] [Show] [Resize] [History] [Profile]

test text

 

 

 

 

Using the try structure

You can use the try feature in Java 7. This ensures that the file will be closed and disposed of even if the read fails.

• If the file is missing then the exception will be raised and caught.

.

import java.io.BufferedReader; import java.io.FileReader; public class Demo{ public static void main(String[] argv){ try(BufferedReader br = new BufferedReader(new FileReader("hggis.txt"))) { for(String line = br.readLine();line!=null;line=br.readLine()) System.out.println(line); } catch(Exception ex){ System.err.println("Exception handled: "+ex); } } }

[Font] [Default] [Show] [Resize] [History] [Profile]

test text

 

 

 

 

Using the try structure

You can use the streams from Java 8.

• In the forEach statement there is a lambda expression - s is a string in this

.

import java.nio.file.*; import java.util.stream.Stream; public class Demo{ public static void main(String[] argv)throws Exception{ try (Stream<String> st = Files.lines(Paths.get("haggis.txt"))) { st.forEach(s -> System.out.println(s)); } } }

[Font] [Default] [Show] [Resize] [History] [Profile]

test text