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How to remove old data from text file using user input in Java

I am trying to get a user input and see if it matches any sentence in a text file. If so I want to remove the sentence. I mean I have the searching implementation so far all I need is help removing the sentence and possibly rewrite to the text file. I am not familiar with Java. Any help would be appreciated.
public static void searchFile(String s) throws FileNotFoundException {
File file = new File("data.txt");
Scanner keyboard = new Scanner(System.in);
// String lines = keyboard.nextLine();
Scanner scanner = new Scanner(file);
while (scanner.hasNextLine()) {
final String lineFromFile = scanner.nextLine();
if (lineFromFile.contains(s)) {
// a match!
System.out.println(lineFromFile + "is found already");
System.out.println("would you like to rewrite new data?");
String go = keyboard.nextLine();
if (go.equals("yes")) {
// Here i want to remove old data in the file if the user types yes then rewrite new data to the file.
}
}
}
}

I think you can't read and write into file on the same time so, make one temporary file and write all data with replaced text into new file and then move that temp file to original file.
I have appended code bellow, hope this helps.
File f = new File("D:\\test.txt");
File f1 = new File("D:\\test.out");
BufferedReader input = new BufferedReader(new InputStreamReader(System.in));
String s = "test";
BufferedReader br = new BufferedReader(new FileReader(f));
PrintWriter pr = new PrintWriter(f1);
String line;
while((line = br.readLine()) != null){
if(line.contains(s)){
System.out.println(line + " is found already");
System.out.println("would you like to rewrite new data?");
String go = input.readLine();
if(go.equals("yes")){
System.out.println("Enter new Text :");
String newText = input.readLine();
line = line.replace(s, newText);
}
}
pr.println(line);
}
br.close();
pr.close();
input.close();
Files.move(f1.toPath(), f.toPath(), StandardCopyOption.REPLACE_EXISTING);

Java Delete Line from File

the code below is from a reference i saw online, so there might be some similarities i'm trying to implement the code to remove an entire line based on the 1st field in this instance it is (aaaa or bbbb) the file which has a delimiter "|", but it is not working. Hope someone can advise me on this. Do i need to split the line first? or my method is wrong?
data in player.dat (e.g)
bbbb|aaaaa|cccc
aaaa|bbbbbb|cccc
Code is below
public class testcode {
public static void main(String[] args)throws IOException
{
File inputFile = new File("players.dat");
File tempFile = new File ("temp.dat");
BufferedReader read = new BufferedReader(new FileReader(inputFile));
BufferedWriter write = new BufferedWriter(new FileWriter(tempFile));
Scanner UserInput = new Scanner(System.in);
System.out.println("Please Enter Username:");
String UserIn = UserInput.nextLine();
String lineToRemove = UserIn;
String currentLine;
while((currentLine = read.readLine()) != null) {
// trim newline when comparing with lineToRemove
String trimmedLine = currentLine.trim();
if(trimmedLine.equals(lineToRemove)) continue;
write.write(currentLine + System.getProperty("line.separator"));
}
write.close();
read.close();
boolean success = tempFile.renameTo(inputFile);
}
}

Your code compares the entire line it reads from the file to the user name the user enters, but you say in your question that you actually only want to compare to the first part up to the first pipe (|). Your code doesn't do that.
What you need to do is read the line from the file, get the part of the string up to the first pipe symbol (split the string) and skip the line based on comparing the first part of the split string to the lineToRemove variable.
To make it easier, you could also add the pipe symbol to the user input and then do this:
string lineToRemove = UserIn + "|";
...
if (trimmedLine.startsWith(lineToRemove)) continue;
This spares you from splitting the string.
I'm currently not sure whether UserInput.nextLine(); returns the newline character or not. To be safe here, you could change the above to:
string lineToRemove = UserIn.trim() + "|";

reading String with spaces java

I am trying to read from scanner with spaces, i want to read even the spaces.
for example "john smith" to be read "john smith".
my code is as follow:
when it gets to the space after john it just hangs and doesn't read any more.
any help would be appreciated.
Scanner in = new Scanner(new InputStreamReader(sock.getInputStream()));
String userName = "";
while (in.hasNext()) {
userName.concat(in.next());
}

Scanner.next() returns the next token, delimited by whitespace. If you would like to read the entire line, along with the spaces, use nextLine() instead:
String userName = in.nextLine();

Scanner scan = new Scanner(file);
scan.useDelimiter("\\Z");
String content = scan.next();
or
private String readFileAsString(String filePath) throws IOException {
StringBuffer fileData = new StringBuffer();
BufferedReader reader = new BufferedReader(
new FileReader(filePath));
char[] buf = new char[1024];
int numRead=0;
while((numRead=reader.read(buf)) != -1){
String readData = String.valueOf(buf, 0, numRead);
fileData.append(readData);
}
reader.close();
return fileData.toString();
}

When we use Scanner.next() to read token there is what we call a delimiter, the default delimiter used in by Scanner is \p{javaWhitespace}+ , you can get it by calling Scanner.delimiter(), which is any char that validate the Character.isWhitespace(char). you can use a customized delimiter for your Scanner using Scanner.useDelimiter().
If you want to take one line as a string so you can use nextLine() , if you already know what is the type of the next token in the input stream, scanner gives you a list of method next*() take convert the token to the specified type. see Scanner's doc here for more info.

Scanner reading only half the no. of lines in a file

I am trying to read a file using Scanner Object with the following code -
public void read(){
Scanner scanner = new Scanner(dataFile).useDelimiter("\n");
String line;
int i = 0;
while(scanner.hasNext()){
line = scanner.next();
i++;
}
System.out.println(i);
}
The file which I am trying to read from has 117000 lines, out of which the scanner only reads first 59550 odd lines. It does not throw any exception and simply returns.
When I change the implementation to use a BufferedReader it reads all 117000 lines -
public void read(){
BufferedReader br = new BufferedReader(new InputStreamReader(new FileInputStream(dataFile)));
String line;
int i=0;
while((line = br.readLine())!= null){
i++;
}
System.out.println(i);
}
Can anyone explain why scanner doesn't read all lines ?

One probable reason could be that Scanner's(1KB) buffer limit is less than that of BufferedReader(8KB).

The following program works for me:
Scanner scanner = new Scanner(dataFile);
String line;
int i = 0;
while(scanner.hasNextLine()){
line = scanner.nextLine();
// System.out.println(line); // remove comment for debug
i++;
}
System.out.println(i);
scanner.close();
The changes from the original program are:
Changed hasNext() and next() to hasNextLine() and nextLine(). In this case the default delimiter is fine
Fixed a typo - system.out.println should be System.out.println
Added a comment to print line (and check if the delimiter is OK)
Added scanner.close()

It's probably something to do with the line ending, delimiter used by Scanner.
You should use the methods :
hasNextLine() and nextLine()

Can anyone explain why scanner doesn't read all lines ?
br.readLine also selects lines that end with \r (and not \n). This is one important difference with your Scanner that only reads lines with \n.

Scanning, spliting and assigning values from a text file

I'm having trouble scanning a given file for certain words and assigning them to variables, so far I've chosen to use Scanner over BufferedReader because It's more familiar. I'm given a text file and this particular part I'm trying to read the first two words of each line (potentially unlimited lines) and maybe add them to an array of sorts. This is what I have:
File file = new File("example.txt");
Scanner sc = new Scanner(file);
while (sc.hasNextLine()) {
String line = sc.nextLine();
String[] ary = line.split(",");
I know It' a fair distance off, however I'm new to coding and cannot get past this wall...
An example input would be...
ExampleA ExampleAA, <other items seperated by ",">
ExampleB ExampleBB, <other items spereated by ",">
...
and the proposed output
VariableA = ExampleA ExampleAA
VariableB = ExampleB ExampleBB
...

You can try something like this
File file = new File("D:\\test.txt");
Scanner sc = new Scanner(file);
List<String> list =new ArrayList<>();
int i=0;
while (sc.hasNextLine()) {
list.add(sc.nextLine().split(",",2)[0]);
i++;
}
char point='A';
for(String str:list){
System.out.println("Variable"+point+" = "+str);
point++;
}
My input:
ExampleA ExampleAA, <other items seperated by ",">
ExampleB ExampleBB, <other items spereated by ",">
Out put:
VariableA = ExampleA ExampleAA
VariableB = ExampleB ExampleBB

To rephrase, you are looking to read the first 2 words of a line (everything before the first comma) and store it in a variable to process further.
To do so, your current code looks fine, however, when you grab the line's data, use the substring function in conjunction with indexOf to just get the first part of the String before the comma. After that, you can do whatever processing you want to do with it.
In your current code, ary[0] should give you the first 2 words.

public static void main(String[] args)
{
File file = new File("example.txt");
FileReader fr = new FileReader(file);
BufferedReader br = new BufferedReader(fr);
String line = "";
List l = new ArrayList();
while ((line = br.readLine()) != null) {
System.out.println(line);
line = line.trim(); // remove unwanted characters at the end of line
String[] arr = line.split(",");
String[] ary = arr[0].split(" ");
String firstTwoWords[] = new String[2];
firstTwoWords[0] = ary[0];
firstTwoWords[1] = ary[1];
l.add(firstTwoWords);
}
Iterator it = l.iterator();
while (it.hasNext()) {
String firstTwoWords[] = (String[]) it.next();
System.out.println(firstTwoWords[0] + " " + firstTwoWords[1]);
}
}