At the moment my code does nothing when i input a valid .txt file. I would like to print the number of lines the file contains. Could anyone tell me why nothing is currently happening?
public class Task3
{
public static void main(String[] args) throws FileNotFoundException
{
// instance variables
int characterCount = 0;
int wordCount = 0;
int lineCount = 0;
// create a Scanner object to read in file name from console input
Scanner in = new Scanner(System.in);
System.out.print("Please enter the file name: ");
String filename = in.next();
File inputFile = new File(filename);
// create a Scanner object to read the actual text file
Scanner inFile = new Scanner(inputFile);
int lines = 0;
while (inFile.hasNextLine())
{ // enter while loop if there is a complete line available
in.nextLine();
lines++;
// increase line counter variable
}
System.out.println(lines);
You're not reading lines from the file, you're reading them from standard input.
In this loop:
while (inFile.hasNextLine())
{ // enter while loop if there is a complete line available
in.nextLine();
lines++;
// increase line counter variable
}
You are using the Scanner for System.in, not the scanner you created for the file. So the call to nextLine will wait for your input instead of going to the next line in the file. That's why it seems that nothing is happening.
Replace in.nextLine with inFile.nextLine and it will work.
Change:
in.nextLine();
To:
inFile.nextLine();
Add a System.out.println(inputFile.exists()) to see that you are not creating a new file.
Related
I have a text file:
2|BATH BENCH|19.00
20|ORANGE BELL|1.42
04|BOILER ONION|1.78
I need to get the number of items which is 3 here using JAVA. This is my code:
int Flag=0;
File file = new File("/Users/a0r01ox/Documents/costl-tablet-automation/src/ItemUPC/ItemUPC.txt");
Scanner sc = new Scanner(file);
while (sc.hasNextLine()) {
Flag=Flag+1;
}
It is going in an infinite loop.
Can someone please help? Thank you.
You must get the next line to avoid an endless loop.
int Flag = 0;
File file = new File("/Users/a0r01ox/Documents/costl-tablet-automation/src/ItemUPC/ItemUPC.txt");
Scanner sc = new Scanner(file);
while (sc.hasNextLine()) {
sc.nextLine();
Flag++;
}
while (sc.hasNextLine()) {
Flag=Flag+1;
String line = sc.nextLine(); //Do whatever with line
}
In the code you have written
int Flag=0;
File file = new File("/Users/a0r01ox/Documents/costl-tablet-automation/src/ItemUPC/ItemUPC.txt");
Scanner sc = new Scanner(file);
while (sc.hasNextLine()) { // this line is just checking whether there is next line or not.
Flag=Flag+1;
}
When you write while (sc.hasNextLine()){} it check whether there is nextLine or not.
eg line 1 : abcdefg
line 2: hijklmnop
here your code will just be on line 1 and keep telling you that yes there is a nextLine.
Whereas when you write
while(sc.hasNextLine()){
sc.nextLine();
Flag++;
}
Scanner will read the line 1 and then because of sc.nextLine() it will go to line 2 and then when sc.hasNextLine() is checked it gives false.
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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 am working on a project that involves asking a user for their zip code. Using the zip code provided the program should loop through a .csv file to determine what city they live in. I can read the information in the .csv file but I have no idea how to loop through it to find a specific piece of information.
import java.util.Scanner;
import java.io.*;
public class DetermineCity {
public static void main(String[] args) throws IOException {
String zip = "99820,AK,ANGOON";
Scanner keyboard = new Scanner(System.in);
System.out.println("enter then name of a file");
String filename = keyboard.nextLine();
File file = new File(filename);
Scanner inputFile = new Scanner(file);
String line = inputFile.nextLine();
System.out.println("The first line in the file is ");
System.out.println(line);
inputFile.close();
}
}
Use Scanner.hasNext() method to loop
String Details="";
int ZipCodeIndex=0;
String ZipCode = "10230"
Scanner inputFile = new Scanner(file);
while(inputFile.hasNext()){
String x=inputFile.nextLine();
String[] arr=x.split(",");
if(ZipCode.equals(arr[ZipCodeIndex]))
{
Details=x;
break;
}
}
This assumes the format of your file is of the form "2301,Suburb, City, Country"
the .nextLine() function returns a String of the next line, however return null if their isn't a line. So using a while loop you can go through your file and store each line in a string.
Then using .split() method you would break this string using a delimiter ",". This would be stored in an array.
Then compare the user zip code with the first value of the array. If they match then you have an array with the city and other information. Then a break statement as you have found the city.
String suburb;
String[] lineArray;
String line = null;
while((line = inputFile.nextLine()) != null){
lineArray[] = line.split(",");
if(lineArray[0] == zipCodeString){
suburb = lineArray[1];
break;
}
}
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.
Here a user enters a list of 1's and 0's.... so an input would 10001010. However I want it to read from a text file... my text file input.txt also containes 10001010... need the coverDataArray array to be fed the same string from the console as from a file.
I tried Datainput stream however, it throws me the exception
'
Scanner in = new Scanner (System.in);
String data1="";
...
.....
try{
System.out.println("Enter the binary bits");
data1 = in.next();
for ( int i = 0; i < data1.length(); i++)
{
covertDataArray[i] = Byte.parseByte(data1.substring( i, i+1));
}'
You can pass a File Object instead of System.in to Scanner constructor. Try it as shown below:
String fileName = "input.txt";
File file = new File(fileName);
Scanner scanner = new Scanner(file);
String s = "";
while(scanner.hasNextLine()){
s = scanner.nextLine();
// your code. You can also use scanner.next() to read word by word instead of nextLine()
}
Byte.parseByte(data1.substring( i, i+1));
Your exception is caused by the fact that you're going up to length - 1, then length - 1 + 1, which is length, which is goign to cause your ArrayOutOfBoundsException. This can be seen on this line:
covertDataArray[i] = Byte.parseByte(data1.substring( i, i+1));
At one point, i is equal to length-1, or the last index in your String. You then attempt to access the next element, which doesn't exist.
And as for your file, you can pass a File object into the Scanner.
Example
Either..
File file = new File("yourfile.txt");
Scanner s = new Scanner(file);
You are trying to use Byte.parseByte as a methode of parsing binairy input, this doesn't really work as parseByte will try to take a numerical input and parse it into a number between -128 and 127. You should use a different method.