How to make a copy of a file in Android?

Master your resources, prevent leaks

Autopilot closure of streams

To prevent Ghosts of Memory Leaks Past (API 19+) Java introduced automatic stream closure with try-with-resources:

// It's like a mini-cleanup crew for your I/O operations
try (FileChannel srcChannel = new FileInputStream(src).getChannel();
     FileChannel destChannel = new FileOutputStream(dest).getChannel()) {
    srcChannel.transferTo(0, srcChannel.size(), destChannel);
}
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This ensures your streams bid you farewell properly once their job is done.

Copy large files, don't break a sweat

Copying large files? Use FileChannel.transferTo! But remember, it's a 2GB cap to keep things civil. You may want a loop or checking the return value for a more thorough transfer:

long position = 0;
long size = srcChannel.size();
// It's not an endless loop, it's a while of persistence!
while (position < size) {
    position += srcChannel.transferTo(position, size - position, destChannel);
}
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Kotlin to the rescue

Kotlin's got your back with copyTo extension function - simple, clean, and plays nice with overwrite:

val srcFile = File(srcPath)
val destFile = File(destPath)
// No treasure chest metaphors here, straight to the point
srcFile.copyTo(destFile, overwrite = true)
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Pro tips and tricks for seamless file copying

Easy file clone for up-to-date Android

On Android API 26+, file duplication got another tool - the Files.copy(). Efficient, minimalistic, and plays nice with the exception Catch'em All:

Path copied = Files.copy(sourcePath, destPath);
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Recursive copying of directories

Directory copying needs more work. Here's where recursion with Files.walkFileTree comes into play:

Files.walkFileTree(srcDir.toPath(), new SimpleFileVisitor<Path>() {
    @Override
    public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
        // File copying is serious business, no place for heebie-jeebies here
        return copy(file);
    }
    
    private FileVisitResult copy(Path file) throws IOException {
        Files.copy(file, targetDir.resolve(srcDir.relativize(file)));
        return FileVisitResult.CONTINUE;
    }
});
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Fail-safe error handling

Don’t forget a nice and cozy try-catch block for your file operations:

try {
    Files.copy(srcPath, destPath);
} catch (IOException e) {
    // "Bummer! An exception! Let's handle it like a champ"
}
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And for pre-API 19 versions, do your cleanup in the finally block if not using try-with-resources.

Check before you act

Before any copy operation, ensure source and destination are not figments of imagination:

if (!srcFile.exists()) {
    // "Oopsie daisy, source file is a no-show!"
}
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References