How can I store a sentence from a file to a string, and then store the next line, which is made up of numbers, to a string?
When I use hasNextline or nextLine, none of it works. I am so confused.
Scanner kb = new Scanner(System.in);
String secretMessage = null;
String message, number = null;
File file = new File(System.in);
Scanner inputFile = new Scanner(file);
while(inputFile.hasNext())
{
message = inputFile.nextLine();
number = inputFile.nextLine();
}
System.out.println(number + "and " + message);
You're looping over the entire file, overwriting your message and number variables, and then just printing them once at the end. Move your print statement inside the loop like this so it will print every line.
while(inputFile.hasNext())
{
message = inputFile.nextLine();
number = inputFile.nextLine();
System.out.println(number + "and " + message);
}
One suggestion I would have for reading lines from a file would be to use the Files.readAllLines() method.
import java.io.BufferedWriter;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.List;
public class Display_Summary_Text {
public static void main(String[] args)
{
String fileName = "//file_path/TestFile.txt";
try
{
List<String> lines = Files.readAllLines(Paths.get(fileName), Charset.defaultCharset());
String eol = System.getProperty("line.separator");
for (int i = 0; i <lines.size(); i+=2)
{
System.out.println(lines.get(i).toString() + "and" + lines.get(i+1) + eol);
}
}catch(IOException io)
{
io.printStackTrace();
}
}
}
Using this set up, you can also create a stringBuilder and Writer to save the output to a file very simply if needed.
Related
My apologies for the title wording, it was hard to explain in words.
What I am trying to do I this:
I have a .txt file that has
cheese cracker salt
bread butter ham
I want the user to be able to enter 'cheese' then type in pepper which will in turn update the file to become
cheese cracker pepper
bread butter ham
I am unsure how to go about editing the third word after I have the user input the first word.
Your algorithm could look like this:
read in the file
split it up by spaces (you will get an array)
put the result into a modifiable list (you can't easily insert into an array)
search for the index of a word
insert another entry by index (you can calculate the correct index from the result of step 4)
overwrite the file with the contents of the list, separated by additional spaces.
Here is a solution utilizing File module along with BufferedReader/BufferedWriter
packages
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.List;
import java.util.Scanner;
import java.nio.file.*;
Driver program
public class Main{
public static void main(String[] args) throws IOException{
Scanner sc = new Scanner(System.in);
System.out.println("Enter the file name: ");
String path = sc.nextLine();
Path p = Paths.get(path);
List <String> lines = Files.readAllLines(p);
System.out.println("Enter new word:");
String newWord = sc.nextLine();
System.out.println("Which word would you like " + newWord + " to replace?");
String oldWord = sc.nextLine();
for(int i = 0; i < lines.size(); i++){
String line = lines.get(i);
line = line.replace(oldWord, word); // if current word is old word, replace with new one
lines.set(i, line); // update list
}
readFile(path); // read here will output original list
writeListToFile(lines, path); // overwrite sample.txt file
readFile(path); // read here will output updated text file from path
sc.close();
}
helper functions
public static void readFile(String fileName){
try{
FileReader fr = new FileReader(fileName);
BufferedReader br = new BufferedReader(fr);
String line = br.readLine();
while(line != null){
System.out.println(line);
line = br.readLine();
}
br.close();
}catch(IOException e){
System.out.println("Error reading file");
}
}
public static void writeListToFile(List<String> list, String path){
try{
FileWriter fw = new FileWriter(path);
BufferedWriter bw = new BufferedWriter(fw);
for(int i = 0; i < list.size(); i++){
bw.write(list.get(i));
bw.newLine();
}
bw.close();
}catch(IOException e){
System.out.println("Error writing to file");
}
}
}
This program is supposed to take in user input about a players name, assists, games played, scores, etc and print it in a .txt file. When the updateData(); method is called I want to be able to ask the user for the players name and what data they want to update, then i should be able to edit that specific part of the text. how could i go about doing this?
Main Class
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileReader;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.Scanner;
public class TextReader {
public static void main(String[] args) throws IOException {
Path path = Paths.get("/Users/Coding/Desktop/myFile.txt").toAbsolutePath();
try (Scanner scan = new Scanner(System.in);
BufferedReader fileReader = new BufferedReader(new FileReader(String.valueOf(path)));
BufferedWriter fileWriter = Files.newBufferedWriter(path, StandardCharsets.UTF_8)) {
Reader reader = new Reader(scan, path, fileWriter, fileReader);
reader.menu();
} catch (IOException e) {
e.printStackTrace();
}
}
}
Reader Class
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.nio.file.Path;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.util.Scanner;
public class Reader {
Path path;
Scanner scan;
BufferedWriter fileWriter;
BufferedReader fileReader;
Reader(Scanner scan, Path path, BufferedWriter fileWriter, BufferedReader fileReader) {
this.scan = scan;
this.path = path;
this.fileWriter = fileWriter;
this.fileReader = fileReader;
}
public void menu() throws IOException {
String task;
do{
System.out.print("What would you like to do today?: ");
task = scan.nextLine();
switch (task) {
case "1":
addData();
break;
case "2":
updateData();
break;
case "6":
System.out.println("Goodbye!");
System.exit(0);
}
}while(!task.equals("6"));
}
void addData() throws IOException {
boolean cont;
DateTimeFormatter log = DateTimeFormatter.ofPattern("yyyy/MM/dd HH:mm:ss");
LocalDateTime time = LocalDateTime.now();
String logTime = log.format(time);
do try {
System.out.print("Enter Name of Player: ");
String playerName = scan.nextLine();
System.out.print("Enter Number of Games Played: ");
int gamesPlayed = Integer.parseInt(scan.nextLine());
System.out.print("Enter Number of Goals Made: ");
int goals = Integer.parseInt(scan.nextLine());
System.out.print("Enter Number of Assists Made: ");
int assists = Integer.parseInt(scan.nextLine());
System.out.print("Enter Number of Points Scored: ");
int points = Integer.parseInt(scan.nextLine());
System.out.print("Enter Number of Saves Made: ");
int saves = Integer.parseInt(scan.nextLine());
System.out.print("Enter Number of Shots Made: ");
int shotsOnGoal = Integer.parseInt(scan.nextLine());
fileWriter.write(
playerName + " " + gamesPlayed + " " + goals + " " +
assists + " " + points + " " + saves + " " + shotsOnGoal + " (" + logTime + ") \n");
cont = false;
} catch(NumberFormatException e){
System.out.println("Enter Valid Input");
cont = true;
}while(cont);
}
void updateData() throws IOException {
System.out.print("Enter Player Name To Edit Data: ");
String playerName = scan.nextLine();
System.out.print("Enter Stat You Want To Change: ");
String stat = scan.nextLine().toLowerCase().trim();
if(fileReader.readLine().contains(playerName)){
String statSearch = fileReader.readLine();
}
}
}
}
Text File Format:
Name GP G A P S S%
Bobby 2 3 6 14 7 50
George 1 3 14 2 9 23
So if the user wanted to edit Name: George, type: Assists, the value 14 beside Georges name only would be edited
I have tried using an if statement to locate the string in the text and append it but I could not figure out how to only change the specified number without changing all the numbers found. Ex: if in the example above 14 is appended both would be changed instead of the one
If you are allowed for this project (i.e., not a school assignment), I recommend using JSON, YAML, or XML. There are too many Java libraries to recommend for using these types of files, but you can search "Java JSON library" for example.
First, need to address some issues...
It's not good practice to put Scanner scan = new Scanner(System.in); in a try-with-resource. It will auto-close System.in and won't be useable after being used in your Reader class. Instead, just do this:
Scanner scan = new Scanner(System.in);
Reader reader = new Reader(scan, path, fileWriter, fileReader);
Or, even better, don't pass it to the constructor, but just set scan to it in the constructor as this.scan = new Scanner(System.in);
Next, for fileReader, you can just initialize it similarly as you did for fileWriter:
BufferedReader fileReader = Files.newBufferedReader(path, StandardCharsets.UTF_8);
Next, this line:
BufferedWriter fileWriter = Files.newBufferedWriter(path, StandardCharsets.UTF_8)
Every time this program is run, this line will overwrite the file to empty, which is probably not what you want. You could add StandardOpenOption.APPEND, but then this means you'll only write to the end of the file.
When you update data, you also have the issue that you'll need to "push" down all of the data that comes after it. For example:
Bobby 1 2 3 4 5
Fred 1 2 3 4 5
If you change the name Bobby to something longer like Mr. President, then it will overwrite the data after it.
While there are different options, the best and simplest is to just read the entire file and store each bit of data in a class (name, scores, etc.) and then close the fileReader.
Then when a user updates some data, change that data (instance variables) in the class and then write all of that data to the file.
Here's some pseudo-code:
class MyProg {
// This could be a Map/HashMap instead.
// See updateData().
public List<Player> players = new ArrayList<>();
public void readData(String filename) throws IOException {
Path path = Paths.get(filename);
try(BufferedReader fileReader = Files.newBufferedReader(path, StandardCharsets.UTF_8)) {
// Read each Player (using specific format)
// and store in this.players
}
}
public void writeData(String filename) throws IOException {
Path path = Paths.get(filename);
try(BufferedWriter fileWriter = Files.newBufferedWriter(path, StandardCharsets.UTF_8)) {
// Write each Player from this.players in specific format
}
}
public void updateData() {
// 1. Find user-requested Player from this.players
// 2. Update that specific Player class
// 3. Call writeData()
// If you are familiar with Maps, then it would be faster
// to use a Map/HashMap with the key being the player's name.
}
}
class Player {
public String name;
public int games;
public int goals;
//...
}
I am writing a program that lets the user enter up to 9999 accounts into a text file, however the issue i'm having is that they can be put in any order, but I have to print them in a sequential order. Here's my code
import java.nio.file.*;
import java.io.*;
import java.nio.channels.FileChannel;
import java.nio.ByteBuffer;
import static java.nio.file.StandardOpenOption.*;
import java.util.Scanner;
import java.text.*;
public class CreateBankFile {
public static int lines = 0;
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
Path file = Paths.get("/root/sandbox/BankAccounts.txt");
String line = "";
int acctNum = 0;
String lastName;
double bal;
final int QUIT = 9999;
try
{
OutputStream output = new BufferedOutputStream(Files.newOutputStream(file));
BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(output));
while(acctNum != QUIT)
{
System.out.print("Enter the acct num less than 9999: ");
acctNum = input.nextInt();
if(acctNum == QUIT)
{
continue;
}
System.out.print("Enter a last name: ");
lastName = input.next();
if(lastName.length() != 8)
{
if(lastName.length() > 8)
{
lastName = lastName.substring(0, 8);
}
else if(lastName.length() < 8)
{
int diff = 8 - lastName.length();
for(int i = 0; i < diff; i++)
{
lastName += " ";
}
}
}
System.out.print("Enter balance: ");
bal = input.nextDouble();
line = "ID#" + acctNum + " " + lastName + "$" + bal;
writer.write(line);
writer.newLine();
lines++;
}
writer.close();
}
catch(IOException e)
{
System.out.println("Error");
}
}
}
My question being, how can I get it so that when the user inputs "55" for example, it is printed to the 55th line of the text file?
You can do something like this :
1) create a class that will store your line ( acctNum , lastName .. etc )
2) in your method , create an arraylist of the class you created , for a given number "n" , your method will parse all the lines , if acctNum is less than "n" , you will create a new instance using this line and add it to your arraylist
3) you will sort the arraylist using the acctNum and then print its content
Perhaps FileChannels would work for you:
RandomAccessFile writer = new RandomAccessFile(file, "rw");
FileChannel channel = writer.getChannel();
ByteBuffer buff = ByteBuffer.wrap("Test write".getBytes(StandardCharsets.UTF_8));
channel.write(buff,5);//5 is the distance in the file
Lots of good examples on the web.
In your question I think you are taking acctNum as line number and you want to add a line at this line number in the file so you can do something like this.
List<String> readLines = Files.readAllLines(path, StandardCharsets.UTF_8);
readLines.set(acctNum- 1, data);
Files.write(path, lines, StandardCharsets.UTF_8);
I assumed that you are using Java 7 or higher so I did acctNum-1 because in Java 7 or higher version line number starts with 1 in rest it starts with 0 so you can change to acctNum.
Reference: List set() and NIO
This is my assignment - Write a program that reads a file and removes all comma’s from it and writes it back out to a second file. It should print to the console window, at the end, the number of comma’s removed.
The program needs to:
Prompt the user for the name of the file to read.
Reads file
Write the non-comma characters to output.txt, including all spaces.
When done reading the input file, write the total number of comma’s removed to the console window.
For example, if the input file contains 3+,2 = 5m, 7%,6 =1 hello
Then the output.txt file should contain:
3+2=5m 7%6=1 hello
And the console window should print “Removed 3 commas”.
Right now I'm having trouble actually removing commas from my input file, I think I would write the line under my last if statment.
Tried figuring out how to remove commas from the input file
package pkg4.pkg4.assignment;
import java.util.Scanner;
import java.io.*;
/**
*
* #author bambo
*/
public class Assignment {
/**
* #param args the command line arguments
*/
public static void main(String[] args) throws IOException {
Scanner keyboard = new Scanner(System.in);
System.out.println("What is the name of the inputfile?");
String inputfile = keyboard.nextLine();
File f = new File(inputfile);
Scanner inputFile = new Scanner(f);
System.out.println("Please enter the output file");
String outputfile = keyboard.nextLine();
FileWriter fw = new FileWriter(outputfile);
PrintWriter pw = new PrintWriter(fw);
int lineNumber=0;
while(inputFile.hasNext());
lineNumber++;
int commacount = 0;
String line = inputFile.nextLine();
if (line.length () != 0)
commacount++;
for(int i=0; i< line.length(); i++)
{
if(line.charAt(i) == ',');
{
commacount++;
}
pw.println("removed " + commacount + "commas");
}
}
}
According to your requirement for program i am suggesting you to use java 8 classes.for simplicity.
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.Scanner;
public class Assignment {
public static void main(String[] args) throws IOException {
String content = "";
Scanner keyboard = new Scanner(System.in);
System.out.println("What is the name of the input file?");
String inputfile = keyboard.nextLine();
content = new String(Files.readAllBytes(Paths.get(inputfile)));
long total_numbers_of_char = content.chars().filter(num -> num == ',').count();
System.out.println("Please enter the output file");
content = content.replaceAll(",", "");
String outputfile = keyboard.nextLine();
Files.write(Paths.get(outputfile), content.getBytes());
System.out.println("removed " + total_numbers_of_char + " commas");
keyboard.close();
}
}
To print on console you should be using :
System.out.println("removed " + commacount + "commas");
To write the line in the output file without the commas :
pw.println(line.replaceAll(",",""));
The goal of this code is to read a file and add numbers to the end of every {(curly bracket) but the file does not output each line like it does in the file but it out puts it into one entire line. where do I put a System.out.println statement. I tried every where and it keeps repeating it
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;
public class Test {
public static void main(String args[]) {
readFile();
}
public static void readFile() { // Method to read file
Scanner inFile = null;
String out = " ";
try {
Scanner input = new Scanner(System.in);
System.out.println("enter file name");
String filename = input.next();
File in = new File(filename); // ask for the file name
inFile = new Scanner(in);
int count = 0;
while (inFile.hasNextLine()) { // reads each line
String line = inFile.nextLine();
for (int i = 0; i < line.length(); i++) {
char ch = line.charAt(i);
out = out + ch;
if (ch == '{') {
count = count + 1;
out = out + " " + count + " ";
} else if (ch == '}') {
out = out + " " + count + " ";
if (count > 0) {
count = count - 1;
}
}
}
}
System.out.println(out);
} catch (FileNotFoundException exception) {
System.out.println("File not found.");
}
inFile.close();
}
}
where do I put a System.out.println statement
The entire output is built in a single string that is not printed until the end, so adding System.out.println statements in the line loop won't help. You can add line breaks to the string by doing:
out += "\n";
Or, at the end of the body of your line loop, print the current line, and reset the buffer for the next line:
System.out.println(out);
out = "";
Using a String for the output buffer is not efficient by the way. String is immutable, so every + statement is copying and duplicating all of the previous characters to create a new object, every time. Consider declaring out as a StringBuilder rather than a String. Then you can add to it with the .append() method and it will not copy all the text every time because a StringBuilder is mutable.