Can Java Rename a File to an Existing Filename and Append its Contents?

Renaming Files with Java

Renaming files is a fundamental task in many programming scenarios. Java provides various methods to efficiently rename files, even when they already exist.

Can we rename a file to an existing name?

Yes, it is possible to rename a file to an existing name. However, if the existing file contains data, it will be overwritten.

How to rename a file to an existing name and append its contents to the original file?

To append the contents of a renamed file to an existing file, follow these steps:

1. Rename the file using file.renameTo(file2).
2. Check if the renaming operation succeeded.
3. If successful, use java.io.FileWriter to open the existing file in append mode (FileWriter(file2, true)).
4. Write the contents of the renamed file to the existing file using FileWriter.write().
5. Close the FileWriter.

Example:

File file = new File("oldname");
File file2 = new File("test1.txt");

if (file2.exists()) {
    // FileWriter opened in append mode
    FileWriter out = new FileWriter(file2, true);
    // Get the contents of file
    String contents = new String(Files.readAllBytes(file.toPath()));
    // Write the contents to the existing file
    out.write(contents);
    out.close();
}

boolean success = file.renameTo(file2);

if (success) {
    System.out.println("File renamed successfully");
} else {
    System.out.println("File was not renamed");
}

This code will rename the file "oldname" to "test1.txt" and append its contents to the existing "test1.txt" file.

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