Java program to write data into a file:

import java.io.FileWriter;

import java.io.IOException;

public class WriteToFile {

public static void main(String[] args) {

// Specify the file path

String filePath = "output.txt";

try {

// Create a FileWriter object with the specified file path

FileWriter writer = new FileWriter(filePath);

// Write data into the file

writer.write("Hello, World!\n");

writer.write("This is a Java program to write into a file.\n");

// Close the FileWriter object

writer.close();

System.out.println("Data has been written into the file successfully.");

} catch (IOException e) {

System.out.println("An error occurred while writing to the file.");

e.printStackTrace();

}

}

}

```

Explanation:

1. We specify the file path where we want to write the data. In this example, the file will be created in the same directory as the Java program.

2. Inside the `try` block, we create a `FileWriter` object with the specified file path.

3. We use the `write()` method of the `FileWriter` object to write data into the file. We can call this method multiple times to write multiple lines of data.

4. After writing the data, we close the `FileWriter` object using the `close()` method.

5. If an exception occurs during the file writing process, we catch the `IOException` and print the error message and stack trace.