To see if a file name exists simply check it as follow:
File file = new File(filePath);
if (file.exists()) {
// do something
}
Note that the file can be also a directory, not necessarelly a true file.
If you need also to check if it is a file:
File file = new File(filePath);
if (file.exists() && !file.isDirectory()) {
// do something
}
solved How to Check if the File Name is already exists or not? [duplicate]