Reading and Writing from & to files are another important part of any programming language.
Without much history, lets learn how to Read files.
Let's assume you want to read a file on your desktop named
test.txtand your java program also is on your desktop.
text.txthas the following lines:
"Hello World of Java"
"I am reading a file"
import java.io.*;
class ReadFile{
public static void main(String[] args){
File file = new File("text.txt");
try(FileReader fr = new FileReader(file);
BufferedReader br = new BufferedReader(fr);){
String line;
while((line = br.readLine()) != null){
System.out.println(line);
}
}catch(IOException ioe){
System.out.println(ioe.getMessage());
}
}
}
To run it in the terminal, type
// -> Java 10 and below
javac ReadFile.java
java ReadFile
// -> Java 11 and above (no need to compile it first)
java ReadFile.java
// output
Hello World of Java
I am reading a file
Time to break it down a little.
File file = new File("text.txt");
// The File class does not create a file,
// It only holds the location/path of the file.
//eg:
File file = new File("path-to-file");
String line;
while((line = br.readLine()) != null)
...
// can also be written as
String line = br.readLine();
while(line != null){
System.out.println(line);
line = br.readLine(); // reads the line again
}
try(FileReader fr = new FileReader(file);
BufferedReader br = new BufferedReader(fr);){
...
This try(...){ closes the FileReader and BufferedReader automatically for us. Read more about try-with-resource in my other post;
Thanks for reading. Next up, we will learn how to write/create a file.
Please leave your comments and any questions you might have.
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