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Java create a new file, or, override the existing file

What I want to achieve is to create a file regardless of whether the file exists or not.
I tried using File.createNewFile() but that will only create the file if it does not already exists. Should I use File.delete() and then File.createNewFile()?
Or is there a clearer way of doing it?

FileWriter has a constructor that takes 2 parameters too: The file name and a boolean. The boolean indicates whether to append or overwrite an existing file. Here are two Java FileWriter examples showing that:
Writer fileWriter = new FileWriter("c:\\data\\output.txt", true); //appends to file
Writer fileWriter = new FileWriter("c:\\data\\output.txt", false); //overwrites file

You can use a suitable Writer:
BufferedWriter br = new BufferedWriter(new FileWriter(new File("abc.txt")));
br.write("some text");
It will create a file abc.txt if it doesn't exist. If it does, it will overwrite the file.
You can also open the file in append mode by using another constructor of FileWriter:
BufferedWriter br = new BufferedWriter(new FileWriter(new File("abc.txt"), true));
br.write("some text");
The documentation for above constructor says:
Constructs a FileWriter object given a File object. If the second
argument is true, then bytes will be written to the end of the file
rather than the beginning.

Calling File#createNewFile is safe, assuming the path is valid and you have write permissions on it. If a file already exists with that name, it will just return false:
File f = new File("myfile.txt");
if (f.createNewFile()) {
// If there wasn't a file there beforehand, there is one now.
} else {
// If there was, no harm, no foul
}
// And now you can use it.

how can i add data in to json file in java?

i want to add data inside of an existing json file..
this is my code:
JsonWriterWithGui(){
if(ae.getSource() == btn_submit){
String lname = (String)lbl_name.getText().toString();
String ladd = (String)lbl_add.getText().toString();
String lcontact = (String)lbl_contact.getText().toString();
FileWriter jsonFileWriter = new FileWriter( "E:\\"+tsave+".json");
jsonFileWriter.write(jsonObject.toJSONString());
jsonFileWriter.flush();
jsonFileWriter.close();
this code is already working. but I am trying to update a json file that already exists.

This is a bit of a guess because the problem you're having isn't entirely clear from the question, but if you're finding that your writes are overwriting instead of appending then try changing this line:
FileWriter jsonFileWriter = new FileWriter( "E:\\"+tsave+".json");
...to this:
FileWriter jsonFileWriter = new FileWriter("E:\\"+tsave+".json", true);
You see, FileWriter is backed by FileOutputStream, which takes a boolean argument saying whether new content should be appended or not. This boolean is false by default so if you want to append then you need to explicitly say so.

Text File writing in Java

I am writing String content to text file in Java code but after writing saving file onto disk, I am getting Incorrect encoding exception, Please suggest me correct Java Code?
String content =fileContent;//fileContent.toString();
System.out.println("File Contt===>"+content);
File fileWrite = new File("/homeDesktop/NormalFile/"+filename);
// if file doesnt exists, then create it
if (!fileWrite.exists()) {
fileWrite.createNewFile();
}
FileWriter fw = new FileWriter(fileWrite.getAbsoluteFile());
BufferedWriter bw = new BufferedWriter(fw);
bw.write(fileContent);
bw.close();

IOUtils.toString(String) Converts your coding.
String not encoded in UTF-8
NOTE:
You dont need this:
// if file doesnt exists, then create it
if (!fileWrite.exists()) {
fileWrite.createNewFile();
}
File create automatically a new file, if there isn't one.

How to replace the contents of a file after processing

Let's say that I have a TreeMap and I want to take all values for a key, make a file with these, pass the file to another process loop and do this for every map key, so I always have to use the same file but its content must be replaced every time for each key.
What I do is:
PrintWriter writeRatings = new PrintWriter("ratings.txt", "UTF-8");
TreeMap<Integer, ArrayList<Rating>> ratings = new TreeMap<Integer, ArrayList<Rating>>();
-->
for(Integer clID:ratings.keySet()){
ArrayList<Rating> ratingGroup = ratings.get(clID);
for(Rating r:ratingGroup){
witer.println(r.toString());
}
}
writer.flush();
writer.close();
With this, I get a file with all the data for each map key. Can you suggest how can I get only the data from the current key each time in the file?

If you want to use the same file and just append lines to it, use a FileWriter and set the append mode to true
PrintWriter writer = new PrintWriter(new FileWriter("filename", true));
This will append lines to the file, instead of over writing the file. This way, different processes can use the same file and keep on adding new data to the file

So what worked for me was to include this line into the for loop in the position of the arrow in the main question post:
PrintWriter writer = new PrintWriter(new FileWriter("filename"));

Writing to an already existing file using FileWriter Java

Is there anyway I can write to an already existing file using Filewriter
For example when the user clicks a submit button:
FileWriter writer = new FileWriter("myfile.csv");
writer.append("LastName");
writer.append(',');
writer.append("FirstName");
writer.append('/n');
writer.append(LastNameTextField.getText());
writer.append(',');
writer.append(FirstNameTextField.getText());
I want to be able to write new data into the already existing myfile.csv without having to recreate a brand new one every time

Yeah. Use the constructor like this:
FileWriter writer = new FileWriter("myfile.csv",true);

FileWriter
public FileWriter(File file,
boolean append)
throws IOException
Constructs a FileWriter object given a File object. If the second argument is true, then bytes will be written to the end of the file rather than the beginning.