Develop Reference

Java Scanner Class ( System.in)

I have the below code that is not reading or infinitely looping when a user inputs text using System.in. If I hard code the text into the Scanner variable it works fine so I am not sure what is wrong with the System.in portion of this code. Any help is appreciated.
import java.util.Scanner; // needed to use the Scanner class
public class HW2 {
static Scanner in = new Scanner(System.in);
public static void main(String [] args) {
System.out.println("Enter your line here");
int the =0;
int and =0;
int is = 0;
int was =0;
int noword =0;
while (in.hasNext()){
String word = in.next();
if (word.equals("the")){
the++;
}
else if( word.equals("and")){
and ++;
}
else if (word.equals("is")){
is++;
}
else if (word.equals("was")){
was++;
}
else noword++;
}
System.out.println("The number of occurrences of the was"+ the);
System.out.println("The number of occurrences of and was"+ and);
System.out.println("The number of occurrences of is was"+ is);
System.out.println("The number of occurrences of was was"+ was);
}
}

As has been mentioned, a Scanner attached to System.in will block while looking for more input. One way to approach this would be to read a single line in from the scanner, tokenize it, and then loop through the words that way. That would look something like this:
//...
String line = in.nextLine(); // Scanner will block waiting for user to hit enter
for (String word : line.split(" ")){
if (word.equals("the")) {
the++;
}
//...
You can always substitute one loop structure (for, while, do-while) for another. They all do the same thing, just with different syntax to make one a bit simpler to use than others depending on the circumstances. So if you want to use a while loop, you can do something like this:
// ...
String line = in.nextLine();
String[] tokens = line.split(" ");
int i = 0;
while (i < tokens.length){
String word = tokens[i];
if (word.equals("the")) {
the++;
}
// ...
i++;
} // end of the while loop
However, I'm of the opinion that a for loop is cleaner in the case of looping over a known set of data. While loops are better when you have an unknown dataset, but a known exit condition.

As System.in is always available while the program is running unless you close it. It will never exit the while loop. So you could add else if (word.equals("exit")) { break; }. This way, whenever you type 'exit' it will close the while loop and execute the code AFTER the while loop.

Depends, do you want to just read 1 line of text and then count the words individually?
Because is you want only one line you could take the input string using the Scanner library and split the string into individual words and apply the if-statement then. Something like:
public static void main(String [] args) {
System.out.println("Enter your line here");
int the =0;
int and =0;
int is = 0;
int was =0;
int noword =0;
String input = in.nextLine();
String words[] = input.split(" ");
for (String s : words) {
if (s.equals("the")){
the++;
} else if( s.equals("and")){
and++;
} else if (s.equals("is")){
is++;
} else if (s.equals("was")){
was++;
} else {
noword++;
}
}
System.out.println("The number of occurrences of the was: "+ the);
System.out.println("The number of occurrences of and was: "+ and);
System.out.println("The number of occurrences of is was: "+ is);
System.out.println("The number of occurrences of was was: "+ was);
}
This way you won't need a while loop at all. So it's more processor and memory efficient.

How would I go about using an integer delimiter? (Java)

So I am trying to read a file using a scanner. This file contains data where there are two towns, and the distance between them follows them on each line. So like this:
Ebor,Guyra,90
I am trying to get each town individual, allowing for duplicates. This is what I have so far:
// Create scanner for file for data
Scanner scanner = new Scanner(new File(file)).useDelimiter("(\\p{javaWhitespace}|\\.|,)+");
// First, count total number of elements in data set
int dataCount = 0;
while(scanner.hasNext())
{
System.out.print(scanner.next());
System.out.println();
dataCount++;
}
Right now, the program prints out each piece of information, whether it is a town name, or an integer value. Like so:
Ebor
Guyra
90
How can I make it so I have an output like this for each line:
Ebor
Guyra
Thank you!

Assuming well-formed input, just modify the loop as:
while(scanner.hasNext())
{
System.out.print(scanner.next());
System.out.print(scanner.next());
System.out.println();
scanner.next();
dataCount += 3;
}
Otherwise, if the input is not well-formed, check with hasNext() before each next() call if you need to break the loop there.

Try it that way:
Scanner scanner = new Scanner(new File(file));
int dataCount = 0;
while(scanner.hasNext())
{
String[] line = scanner.nextLine().split(",");
for(String e : line) {
if (!e.matches("-?\\d+")) System.out.println(e);;
}
System.out.println();
dataCount++;
}
}
We will go line by line, split it to array and check with regular expression if it is integer.
-? stays for negative sign, could have none or one
\\d+ stays for one or more digits
Example input:
Ebor,Guyra,90
Warsaw,Paris,1000
Output:
Ebor
Guyra
Warsaw
Paris

I wrote a method called intParsable:
public static boolean intParsable(String str)
{
int n = -1;
try
{
n = Integer.parseInt(str);
}
catch(Exception e) {}
return n != -1;
}
Then in your while loop I would have:
String input = scanner.next();
if(!intParsable(input))
{
System.out.print(input);
System.out.println();
dataCount++;
}

No Line found error but I don't see how?

Pretty much I'm trying to write a program that counts the words in a text file AND count how many lines as well but I keep getting the no line error.
import java.util.*;
import java.io.*;
public class input {
public static void main(String[] args) throws FileNotFoundException {
String name;
int lineCount = 0;
int wordCount = 0;
File input = new File("C:\\Users\\Ceri\\workspace1\\inputoutput\\src\\inputoutput\\lab1task3.txt");
Scanner in = new Scanner(input);
while(in.hasNextLine()){
while(in.hasNext()){
wordCount++;
in.next();
}
lineCount++;
in.nextLine();
}
System.out.println(lineCount);
System.out.println(wordCount);
in.close();
}
}
The issue lays withing the while(in.hasnextline()) loop.

That is because your inner while loop exhasts all the input characters from your scanner. in.hasNext() does not stop at new line characters.

You are incorrectly implementing hasNextLine() and hasNext() such that you have read through all the tokens in your scanner within your inner while. An easier way to read every word and line would be to implement something like this:
int words = 0;
int lines = 0;
while(in.hasNextLine()) {
lines++;
String line = in.nextLine()
words += new StringTokenizer(line, " ,").countTokens();
}

You are reaching end of the file while looping through the inner loop. Once, it reaches the end of file, it will come out of inner loop. lineCount will be incremented and then, in.nextLine() will be executed. Buffer for Scanner's object is not having any value inside of it, hence you are getting this result.
Try this:
while(in.hasNextLine()){
String line = in.nextLine();
lineCount++;
String[] words = line.split(" ");
wordCount += words.length;
}

Do this
while(in.hasNextLine())
{
Scanner ins=new Scanner(in.nextLine());
while(ins.hasNext())
{
wordCount++;
ins.next();
}
lineCount++;
}

What's wrong with this file Scanner code?

I am trying to search the File for characters in Java language. For that I am using Scanner to scan the file.
Well to check the Heirarchy work, I am using System.out.print("Worked till here!"); so that I can check whether it is executed or not. I was able to execute the code till the last stage, but then I found that the essential boolean variable wasn't altered, which was under the condition to check whether there is a character match or not.
The file contents are as
Ok, here is some text!
Actually this file is created to test the validity of the java application
Java is my favourite programming language.
And I think I can score even more :)
Wish me luck!
However, no matter what I search it always prompts me to be false.
Here is the code I am using
public static void main (String[] args) throws IOException {
// Only write the output here!!!
System.out.print("Write the character to be found in the File: ");
Scanner sc = new Scanner(System.in);
String character = sc.next();
// Find the character
System.out.println("Searching now...");
getCharacterLocation(character);
// Close the resource!
sc.close();
}
The method call executed and the method is as
public static void getCharacterLocation (String character) throws IOException {
System.out.println("File found...");
File file = new File("res/File.txt");
Scanner sc = new Scanner(file);
int lineNumber = 0;
int totalLines = 0;
boolean found = false;
// First get the total number of lines
while(sc.hasNextLine()) {
totalLines++;
sc.nextLine();
System.out.println("Line looping! For Total Lines variable.");
}
int[] lineNumbers = new int[totalLines];
int lineIndex = 0;
System.out.println("Searching in each line...");
while(sc.hasNextLine()) {
// Until the end
/* Get each of the character, I mean string from
* each of the line... */
while(sc.hasNext()) {
// Until the end of line
String characterInLine = sc.next();
if(sc.findInLine(character) != null) {
found = true;
}
}
System.out.print(sc.nextLine() + "\n");
lineNumber++;
sc.nextLine();
}
System.out.println("Searching complete, showing results...");
// All done! Now post that.
if(found) {
// Something found! :D
System.out.print("Something was found!");
} else {
// Nope didn't found a fuck!
System.out.println("Sorry, '" + character +
"' didn't match any character in file.");
}
sc.close();
}
Never mind the extra usage of variables, and arrays. I would use it in further coding if I can get the character and set the value to true.
Here is the output of this program.
Initial Stage
This is the initial stage for that. I wrote Ok in the input field, you can see Ok is the very first character in the File too.
Final Stage
This is the result after the execution.
Any help in this?

You count lines and don't restart the scanner.
boolean found = false;
// First get the total number of lines
while(sc.hasNextLine()) {
totalLines++;
sc.nextLine();
System.out.println("Line looping! For Total Lines variable.");
}
int[] lineNumbers = new int[totalLines];
int lineIndex = 0;
System.out.println("Searching in each line..."); // <------
while(sc.hasNextLine()) {
add e.g.
UPDATED from the comment
sc.close();
sc = new Scanner(file);
before the next while(sc.hasNextLine())

You need to implement a way to string your characters together and check them against your input. It appears that you don't currently have a way to do this in your code.
Try building an array of characters with your scanner, and moving through and doing a check of your input vs the indexes. Or maybe there is a way to implement the tonkenizer class achieve this.
Put remember, what you are looking for is not a character, it is a string, and you need to keep this in mind when writing your code.

When you count your lines you use while(sc.hasNextLine()).
After this loop, your scanner is behind the last line, so when you go to your next loop while(sc.hasNextLine()) { it is never executed.

There are multiple problems with your code:
You Iterated through your scanner here:
while(sc.hasNextLine()) {
totalLines++;
sc.nextLine();
System.out.println("Line looping! For Total Lines variable.");
}
So after this you have to reset it again to read for further processing.
While searching for character you are having two loops:
while(sc.hasNextLine()) {
// Until the end
/* Get each of the character, I mean string from
* each of the line... */
while(sc.hasNext()) {
// Until the end of line
String characterInLine = sc.next();
if(sc.findInLine(character) != null) {
found = true;
}
}
Here you just need a single loop like:
while(sc.hasNextLine()) {
String characterInLine = sc.nextLine();
if(characterInLine.indexOf(character) != -1) {
found = true;
break;
}
}

During while loops, interpret next character?

public class test {
/**
* #param args the command line arguments
*/
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
System.out.println("Please insert a word.: ");
String word = (" ");
while (in.hasNextLine()){
System.out.println(in.next().charAt(0));
}
}
}
I am attempting to read each letter from the input and seperate it with a space.
For example: Input is Yes.
The output should be
Y
E
S
.
I do not understand how to make the char go to the next letter in the input. Can anyone help?

You've got a bug in 'hasNextLine' your loop -- an extraneous ; semicolon before the loop body. The semicolon (do nothing) will be looped, then the body will be executed once.
Once you fix that, you need to loop over the characters in the word. Inside the 'hasNextLine' loop:
String word = in.nextLine();
for (int i = 0; i < word.length(); i++) {
char ch = word.charAt(i);
// print the character here.. followed by a newline.
}

You could do
while (in.hasNext()) {
String word = in.next();
for (char c: word.toCharArray()) {
System.out.println(c);
}
}