I keep getting an error and I am unsure why. This is my code
public class test {
public static void main(String[] args) throws FileNotFoundException {
Scanner inscan = new Scanner(System.in);
System.out.print("Enter input file name: ");
String inputfilename = inscan.nextLine();
File inputfile = new File(inputfilename);
Scanner in = new Scanner(inputfile);
String inputline = in.nextLine();
ArrayList<String> Names = new ArrayList<String>();
in.nextLine();
in.nextLine();
int total = 0;
while(in.hasNextLine()){
in.nextInt();
String Mname = in.next();
int Number = in.nextInt();
Names.add(Mname);
total += Number;
}
in.close();
for (String Mname : Names) {
System.out.println(Mname);
}
System.out.println("total number is " + total);
}
}
Prints:
hi
total number is 38
This is what the text file looks like.
test
test
1 mike 34
2 hi 38
I am first skipping the first two lines. Then getting all the names. Then printing the total number of all those names. It is now working with no errors but only prints one thing.
You're not pointing to the file properly. In order for your program to read names.txt, names.txt must be in the program's root directory. If you're running this from eclipse, that's the project's main folder. If you're running this from something like Dr. Java, this would be wherever your .java file is. Depending on what ide you're using to compile and run this, you can Google where the root directory of your project should be.
When you export this as a .jar file, the root directory becomes the directory from which the .jar is being run.
Edit: nevermind, disregard that, I see that the error is occurring on a different line of code. My bad :/
Edit 2: actually, do NOT disregard that, I just realized I was looking at the right line of code - the txt file's location is likely the problem (I think)
Part of your input routine is done in a loop. I'm guessing it is that way to facilitate the lines which (probably) all follow the same pattern (after the first two lines).
The problem is that your loop reads one line an "bits" of the second line. It is the "bits" of the second line being read that is problematic. Those bits prevent the beginning of the loop from reading where you probably want it to start reading.
I would recommend the loop reading just one line, or doing away with the loop and reading both lines before processing (depending on if the file has many or 2 lines of input).
Your code has three calls to in.nextLine() before it starts scanning line for tokens (ie int ID, name and number). This means it skips the two header lines, but also the first line of data.
I also noticed that you are not advancing to the next line once you have finished scanning tokens. So at the end of your while loop another call to in.nextLine() should get you in the right position for the next iteration.
This seems to work with my local testing:
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;
import java.util.ArrayList;
public class test {
public static void main(String[] args) throws FileNotFoundException {
Scanner inscan = new Scanner(System.in);
System.out.print("Enter input file name: ");
String inputfilename = inscan.nextLine();
File inputfile = new File(inputfilename);
Scanner in = new Scanner(inputfile);
String inputline = in.nextLine();
ArrayList<String> Names = new ArrayList<String>();
in.nextLine();
int total = 0;
while(in.hasNextLine()){
in.nextInt();
String Mname = in.next();
int Number = in.nextInt();
Names.add(Mname);
total += Number;
in.nextLine();
}
in.close();
for (String Mname : Names) {
System.out.println(Mname);
}
System.out.println("total number is " + total);
}
}
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This code is supposed to get N values from the user. Then input the values into a .txt file. I'm having trouble getting the values to show in the .txt file. Not sure why.
// This program writes data into a file.
import java.io.*; // Needed for File I/O class.
import java.util.Scanner; // Needed for Scanner class.
public class program01
{
public static void main (String [] args) throws IOException
{
int fileName;
int num;
// Create a Scanner object for keyboard input.
Scanner input = new Scanner(System.in);
File fname = new File ("namef.txt");
Scanner inputFile = new Scanner(fname); // Create a Scanner object for keyboard input.
FileWriter outFile = new FileWriter ("namef.txt", true);
PrintWriter outputfile = new PrintWriter("/Users/******/Desktop/namef.txt");
System.out.println("Enter the number of data (N) you want to store in the file: ");
int N = input.nextInt(); // numbers from the user through keyboard.
System.out.println("Enter " + N + " numbers below: ");
for ( int i = 1; i <= N; i++)
{
// Enter the numbers into the file.
input.nextInt();
outputfile.print(N);
}
System.out.println("Data entered into the file.");
inputFile.close(); // Close the file.
}
} // End of class
In your program you seemed to have thrown everything and hoping that it works. To find out what class you should use you should search it in Javadoc of you Java version.
Javadoc of Java 12
PrintWriter:
Prints formatted representations of objects to a text-output stream. This class implements all of the print methods found in PrintStream. It does not contain methods for writing raw bytes, for which a program should use unencoded byte streams.
FileWriter:
Writes text to character files using a default buffer size. Encoding from characters to bytes uses either a specified charset or the platform's default charset.
Scanner (File source):
Constructs a new Scanner that produces values scanned from the specified file. Bytes from the file are converted into characters using the underlying platform's default charset.
Now you can see what each class is for. Both PrintWriter and FileWriter are used to write file however PrintWriter offer more formatting options and Scanner(File source) is for reading files not writing files.
Since there is already an answer with PrintWriter. I am writing this using FileWriter.
public static void main(String[] args) throws Exception {
// Create a Scanner object for keyboard input.
Scanner input = new Scanner(System.in);
// You can provide file object or just file name either would work.
// If you are going for file name there is no need to create file object
FileWriter outputfile = new FileWriter("namef.txt");
System.out.print("Enter the number of data (N) you want to store in the file: ");
int N = input.nextInt(); // numbers from the user through keyboard.
System.out.println("Enter " + N + " numbers below: ");
for (int i = 1; i <= N; i++) {
System.out.print("Enter the number into the file: ");
// Writing the value that nextInt() returned.
// Doc: Scans the next token of the input as an int.
outputfile.write(Integer.toString(input.nextInt()) + "\n");
}
System.out.println("Data entered into the file.");
input.close();
outputfile.close(); // Close the file.
}
Output:
Enter the number of data (N) you want to store in the file: 2
Enter 2 numbers below:
Enter the number into the file: 2
Enter the number into the file: 1
Data entered into the file.
File:
2
1
Here's a working variant of what you want to achieve:
import java.io.*; // Needed for File I/O class.
import java.util.Scanner; // Needed for Scanner class.
public class program01
{
public static void main (String [] args) throws IOException
{
int fileName;
int num;
// Create a Scanner object for keyboard input.
Scanner input = new Scanner(System.in);
File fname = new File ("path/to/your/file/namef.txt");
PrintWriter outputfile = new PrintWriter(fname);
System.out.println("Enter the number of data (N) you want to store in the file: ");
int N = input.nextInt(); // numbers from the user through keyboard.
System.out.println("Enter " + N + " numbers below: ");
for (int i = 1; i <= N; i++)
{
// Enter the numbers into the file.
int tmp = input.nextInt();
outputfile.print(tmp);
}
System.out.println("Data entered into the file.");
outputfile.close(); // Close the file.
}
}
Several comments on above:
1) Got rid of redundant rows:
Scanner inputFile = new Scanner(fname); // Create a Scanner object for keyboard input.
FileWriter outFile = new FileWriter ("namef.txt", true);
You actually didn't use them at all.
2) In PrintWriter we pass File object, not String.
3) In for loop there was a logic mistake - on every iteration you should have written N instead of actual number which user entered on console.
4) Another mistake was in closing wrong file in the last line.
EDIT: adding according to comment.
in point 2) there's an alternative way - you can skip creating File object and pass as a String a path to even non-existing file directly in PrintWriter, like this:
PrintWriter outputfile = new PrintWriter("path/to/your/file/namef.txt");
I was having trouble getting my program to read from a file "lexicon.txt"
My task was to have the program scan a user input and getting the word count for the program in return. Do you guys know what's going on in my code?
import java.io.*;
import java.util.Scanner;
public class searchFile {
public static void main (String args[]) throws IOException {
Scanner reader = new Scanner(System.in);
System.out.println("Please enter the file name (e.g: nonamefile.txt)");
String objective = reader.nextLine();
if (!(objective.equals("lexicon.txt"))) {
System.out.println("ERROR: Missing File");
}
else {
Scanner reader2 = new Scanner(System.in);
Scanner lexicon = new Scanner(new File("lexicon.txt"));
int wordCount = 0;
System.out.println("What word do you need to look up?");
String objective2 = reader2.nextLine();
while (lexicon.hasNext()) {
String word = lexicon.next();
if (word.equalsIgnoreCase(objective2)){
wordCount++;
}
}
System.out.println("Word count = " + wordCount);
}
} // end main method (String Args[])
} // end class searchFile
I ran your code on my computer. It is to help you. may be you are not doing same.
Please enter the file name (e.g: nonamefile.txt)
lexicon.txt
What word do you need to look up?
three
Word count = 3
The text I used in lexicon.txt was that :
one
two two
three three three
And it is working fine.
Remember, just copy paste is not like what you think it. there could be any character in clipboard when you copy that you cannot see, and pasting it also pastes these code too in your text file.
Scanner.next() looks for the next string delimited by word boundries.
Suppose there is a text that you copy pasted :
which is not visible in notepad :
So when you will search for "Hello", it will not be there.
You will have to search for instead, but you cannot write this easily.
My code is designed to read the contents of a text file and check if the contents are entered in a format that is as follows:
john : martin : 2 : 1
and if that format is followed then it will output it in the format:
john [2] | martin [1]
or else it will be counted as an invalid result and the total numbers will not be added to it whereas if the results are in the format then they will get added to the total so with the example it would display the number of vaild results as 1, invalid as 0 and total number as 3.
My question is that my code doesn't work properly as I get this error:
Exception in thread "main" java.util.InputMismatchException
at java.util.Scanner.throwFor(Scanner.java:840)
at java.util.Scanner.next(Scanner.java:1461)
at java.util.Scanner.nextInt(Scanner.java:2091)
at java.util.Scanner.nextInt(Scanner.java:2050)
at reader.main(reader.java:33)
So how would I go about fixing this and reading and displaying the data in thee way that I want? Thanks in advance.
import java.io.FileReader;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.Locale;
import java.util.Scanner;
public class reader {
/**
* #param args
* #throws FileNotFoundException
* #throws FileNotFoundException
* #throws FileNotFoundException when the file cannot be loaded
*/
public static void main(String[] args) throws FileNotFoundException {
String hteam;
String ateam;
int hscore;
int ascore;
Scanner s = new Scanner(new BufferedReader(new FileReader("results2.txt"))).useDelimiter(":");
// create a scanner which scans from a file and splits at each colon
while ( s.hasNext() ) {
hteam = s.next(); // read the home team from the file
ateam = s.next(); // read the away team from the file
hscore = s.nextInt(); //read the home team score from the file
ascore = s.nextInt(); //read the away team score from the file
System.out.print(hteam); // output the line of text to the console
System.out.print(hscore);
System.out.print(ateam);
System.out.println(ascore);
}
System.out.println("\nEOF"); // Output and End Of File message.
}
}
You're looking for s.next() instead of s.nextLine().
hteam = s.nextLine() reads the entire line "john : martin : 2 : 1", leaving nothing left for ateam.
Edit:
As you've said this still isn't working, I'd guess that you have an extra newline at the end of your input file, which is causing s.hasNext() to evaluate to true. This would cause the Scanner to trip up when it's getting the next input line.
Try Scanner s = new Scanner(System.in).useDelimiter("\\s*:\\s*|\\s*\\n\\s*"); to read multiple lines.
See implementation: http://ideone.com/yfiR2S
To verify that a line is in the correct format, I'd (with inspiration from osoblanco's answer) check that there are 4 words and that the last two are integers:
public static boolean verifyFormat(String[] words) {
// see endnote for isInteger()
return words.length == 4 && /*isInteger(words[2]) && isInteger(words[3])*/;
}
public static void main(String[] args) throws FileNotFoundException {
String hteam;
String ateam;
int hscore;
int ascore;
Scanner s = new Scanner(new BufferedReader(
new FileReader("results2.txt"))).useDelimiter("\\s*:\\s*|\\s*\\n\\s*");
while (s.hasNext()) {
String line = s.nextLine();
String[] words = line.split("\\s*:\\s*");
if(verifyFormat(words)) {
hteam = words[0]; // read the home team
ateam = words[1]; // read the away team
hscore = Integer.parseInt(words[2]); //read the home team score
ascore = Integer.parseInt(words[3]); //read the away team score
System.out.print(hteam); // output the line of text to the console
System.out.print(hscore);
System.out.print(ateam);
System.out.println(ascore);
}
}
System.out.println("EOF");
}
isInteger() can be found here.
I think scanning isn't quite what you want here. I would just use a BufferedReader and do ReadLine to handle 1 line each time through the for loop.
Then verify each line by the following:
1) String.split(":") and verify 4 pieces.
String [] linePieces = nextLine.split(":");
if(linePieces.length!=4)
{
//mark invalid, continue loop
}
2) Trim each piece
for(int i =0; i<4; i++)
linePieces[i] = linePieces[i].trim();
3) Verify piece 3 and piece 4 are numbers, Integer.parseInt with try/catch. In the catch block, count that the line is invalid.
try
{
name1=linePieces[0];
name2=linePieces[1];
score1=Integer.parseInt(linePieces[2]);
score2=Integer.parseInt(linePieces[3]);
//count as success and do logic
}catch(NumberFormatException e){
//invalid line
}
I am a noobie at programming and I can't seem to figure out what to do.
I am to write a Java program that reads in any number of lines from a file and generate a report with:
the count of the number of values read
the total sum
the average score (to 2 decimal places)
the maximum value along with the corresponding name.
the minimum value along with the corresponding name.
The input file looks like this:
55527 levaaj01
57508 levaaj02
58537 schrsd01
59552 waterj01
60552 boersm01
61552 kercvj01
62552 buttkp02
64552 duncdj01
65552 beingm01
I program runs fine, but when I add in
score = input.nextInt(); and
player = input.next();
The program stops working and the keyboard input seems to stop working for the filename.
I am trying to read each line with the int and name separately so that I can process the data and complete my assignment. I don't really know what to do next.
Here is my code:
import java.io.BufferedReader;
import java.io.FileReader;
import java.util.Scanner;
public class Program1 {
private Scanner input = new Scanner(System.in);
private static int fileRead = 0;
private String fileName = "";
private int count = 0;
private int score = 0;
private String player = "";
public static void main(String[] args) {
Program1 p1 = new Program1();
p1.getFirstDecision();
p1.readIn();
}
public void getFirstDecision() { //*************************************
System.out.println("What is the name of the input file?");
fileName = input.nextLine(); // gcgc_dat.txt
}
public void readIn(){ //*********************************************
try {
FileReader fr = new FileReader(fileName + ".txt");
fileRead = 1;
BufferedReader br = new BufferedReader(fr);
String str;
int line = 0;
while((str = br.readLine()) != null){
score = input.nextInt();
player = input.next();
System.out.println(str);
line++;
score = score + score;
count++;
}
System.out.println(count);
System.out.println(score);
br.close();
}
catch (Exception ex){
System.out.println("There is no shop named: " + fileName);
}
}
}
The way you used BufferReader with Scanner is totally wrong .
Note: you can use BufferReader in Scanner constructor.
For example :
try( Scanner input = new Scanner( new BufferedReader(new FileReader("your file path goes here")))){
}catch(IOException e){
}
Note: your file reading process or other processes must be in try block because in catch block you cannot do anything because your connection is closed. It is called try catch block with resources.
Note:
A BufferedReader will create a buffer. This should result in faster
reading from the file. Why? Because the buffer gets filled with the
contents of the file. So, you put a bigger chunk of the file in RAM
(if you are dealing with small files, the buffer can contain the whole
file). Now if the Scanner wants to read two bytes, it can read two
bytes from the buffer, instead of having to ask for two bytes to the
hard drive.
Generally speaking, it is much faster to read 10 times 4096 bytes
instead of 4096 times 10 bytes.
Source BufferedReader in Scanner's constructor
Suggestion: you can just read each line of your file by using BufferReader and do your parsing by yourself, or you can use Scanner class that gives you ability to do parsing tokens.
difference between Scanner and BufferReader
As a hint you can use this sample for your parsing goal
Code:
String input = "Kick 20";
String[] inputSplited = input.split(" ");
System.out.println("My splited name is " + inputSplited[0]);
System.out.println("Next year I am " + (Integer.parseInt(inputSplited[1])+1));
Output:
My splited name is Kick
Next year I am 21
Hope you can fixed your program by given hints.
I am having trouble with a programming assignment. I need to read data from a txt file and store it in parallel arrays. The txt file contents are formatted like this:
Line1: Stringwith466numbers
Line2: String with a few words
Line3(int): 4
Line4: Stringwith4643numbers
Line5: String with another few words
Line6(int): 9
Note: The "Line1: ", "Line2: ", etc is just for display purposes and isn't actually in the txt file.
As you can see it goes in a pattern of threes. Each entry to the txt file is three lines, two strings and one int.
I would like to read the first line into an array, the second into another, and the third into an int array. Then the fourth line would be added to the first array, the 5th line to the second array and the 6th line into the third array.
I have tried to write the code for this but can't get it working:
//Create Parallel Arrays
String[] moduleCodes = new String[3];
String[] moduleNames = new String[3];
int[] numberOfStudents = new int[3];
String fileName = "myfile.txt";
readFileContent(fileName, moduleCodes, moduleNames, numberOfStudents);
private static void readFileContent(String fileName, String[] moduleCodes, String[] moduleNames, int[] numberOfStudents) throws FileNotFoundException {
// Create File Object
File file = new File(fileName);
if (file.exists())
{
Scanner scan = new Scanner(file);
int counter = 0;
while(scan.hasNext())
{
String code = scan.next();
String moduleName = scan.next();
int totalPurchase = scan.nextInt();
moduleCodes[counter] = code;
moduleNames[counter] = moduleName;
numberOfStudents[counter] = totalPurchase;
counter++;
}
}
}
The above code doesn't work properly. When I try to print out an element of the array. it returns null for the string arrays and 0 for the int arrays suggesting that the code to read the data in isn't working.
Any suggestions or guidance much appreciated as it's getting frustrating at this point.
The fact that only null's get printed suggests that the file doesn't exist or is empty (if you print it correctly).
It's a good idea to put in some checking to make sure everything is fine:
if (!file.exists())
System.out.println("The file " + fileName + " doesn't exist!");
Or you can actually just skip the above and also take out the if (file.exists()) line in your code and let the FileNotFoundException get thrown.
Another problem is that next splits things by white-space (by default), the problem is that there is white-space on that second line.
nextLine should work:
String code = scan.nextLine();
String moduleName = scan.nextLine();
int totalPurchase = Integer.parseInt(scan.nextLine());
Or, changing the delimiter should also work: (with your code as is)
scan.useDelimiter("\\r?\\n");
You are reading line so try this:
while(scan.hasNextLine()){
String code = scan.nextLine();
String moduleName = scan.nextLine();
int totalPurchase = Integer.pasreInt(scan.nextLine().trim());
moduleCodes[counter] = code;
moduleNames[counter] = moduleName;
numberOfStudents[counter] = totalPurchase;
counter++;
}
String code = scan.nextLine();
String moduleName = scan.nextLine();
int totalPurchase = scan.nextInt();
scan.nextLine()
This will move scanner to proper position after reading int.