Here's a Java program that appends text to an existing file:

import java.io.*;

public class FileAppend {
    public static void main(String[] args) {
        String fileName = "example.txt";
        String textToAppend = "This text will be appended to the end of the file.";

        try {
            FileWriter fileWriter = new FileWriter(fileName, true);
            BufferedWriter bufferedWriter = new BufferedWriter(fileWriter);
            PrintWriter printWriter = new PrintWriter(bufferedWriter);

            printWriter.println(textToAppend);
            printWriter.close();

            System.out.println("Text has been appended to the file.");
        } catch (IOException e) {
            System.out.println("An error occurred: " + e);
        }
    }
}

In this program, we define a String variable fileName to hold the name of the file we want to append to, and a String variable textToAppend to hold the text we want to append.

We then create a FileWriter object to write to the file. We pass true as the second argument to the FileWriter constructor, which means that we want to append to the file instead of overwriting it.

Next, we create a BufferedWriter object and pass it the FileWriter object as an argument. We then create a PrintWriter object and pass it the BufferedWriter object as an argument.

Finally, we use the println method of the PrintWriter object to append the text to the file, and we close the PrintWriter object. We also print a message to the console to indicate that the text has been appended to the file.

Note that this program assumes that the file already exists. If the file does not exist, this program will throw an exception. You can add additional code to handle this situation as needed.