Understanding Java File Operations

Input/Output and Streams in Java

Alex Liu

Software Development Engineer

About Alex Liu

M.S. Degree in Computer Science

8 years of experience in the software development industry

6 years of hands-on expertise in Java programming

A cartoon avatar of the instructor

Course overview

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                  Java File Operations
                           Creation
                            Deletion
                Directory management

Course overview

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                  Java File Operations        Iterators and Streams
                           Creation                   Processing collections
                            Deletion                     Transforming data
                Directory management

Course overview

Screenshot 2025-05-20 at 15.47.09.png

                  Java File Operations        Iterators and Streams      Custom Methods and More
                           Creation                   Processing collections               Build scalable                             Deletion                     Transforming data                 Java applications
                Directory management

Creating files

Import the File class
```
import java.io.File;
```

Make a File object named dataTextFile

File dataTextFile = new File("data.txt");

To create the file on the computer, call the .createNewFile() method
```
boolean result = dataTextFile.createNewFile();
```
Returns true if the file is created successfully; false if it already exists
Works for any file type

Deleting files

Create a File object named exampleFile that references the file we want to remove
```
File exampleFile = new File("example.txt");
```
Use the .delete() method to attempt to delete the file
```
boolean deleted = exampleFile.delete();
```
Returns true if the file was deleted
Returns false if file could not be deleted (e.g., due to insufficient permissions)

Checking file existence

The .exists() method returns true if the file exists

// Use `.exists()` to check if a file already exists on our disk
if (dataTextFile.exists()) {
    // Print message if file exists
    System.out.println("The file already exists.");
} else {
    // Attempt to create the file if it doesn't exist
    boolean result = dataTextFile.createNewFile();
}

Helps prevent duplicates

Wrapping file operations with try-catch

Always wrap file operations in a try-catch block
- Handles potential exceptions like IOException
  - From permission errors or invalid files

try {
    //Any file operation
} catch (IOException e) {
    e.getMessage();
}

Let's practice!

Input/Output and Streams in Java