File class
- Java course
- Intermediate
- Lesson 70/116
- 5 min
Learn files and directories with File.
File class for file info
In Java, java.io.File represents the path of a file or directory; it does not read content. You create a File object with File f = new File("notes.txt");. f.exists() tells you if it exists; f.length() gives its byte size.
File only holds path information; reading or writing content requires reader/writer classes. To create a new file, use f.createNewFile().
Creating a file
To create a new file, use the createNewFile() method. It creates the file if it does not exist and returns true; it returns false if the file already exists. Because it can throw IOException, the call must be inside try/catch or the method must declare throws IOException.
This is the first exception management you meet in file operations. Java makes input/output errors checked at compile time; this catches mistakes early.
Practice Check file existence with File
Import the File class with import java.io.File;. Add throws Exception to main. Create a File f = new File("test.txt");, call f.createNewFile() to create it, and print System.out.println(f.exists());. The expected output is true.
Starter code
import java.io.File;
public class Main {
public static void main(String[] args) throws Exception {
// Create a File object and create the file
// Check existence and print
}
}Sample solution
import java.io.File;
public class Main {
public static void main(String[] args) throws Exception {
File f = new File("test.txt");
f.createNewFile();
System.out.println(f.exists());
}
}Expected output
true
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 What does File f = new File("a.txt"); do?
- It writes to the file
- It reads the file and returns its content
- It deletes the file
- It only represents the file path Correct answer
Explanation: A File object holds the path; it does not read or write content.
2 Complete the existence check
if (f.____()) {
System.out.println("Yes");
}if (f.exists()) {
System.out.println("Yes");
}Explanation: exists() checks whether the file exists.
3 Match the File methods
| Term | Meaning |
|---|---|
exists() |
Checks if the file exists |
length() |
Returns the byte size |
createNewFile() |
Creates a new file |
delete() |
Deletes the file |