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How to limit the number of words when reading a line from standard input?

I am new to Stackoverflow and this is my first time asking a question. I have searched my problem thoroughly, however, could not find an appropriate answer. I am sorry if this has been asked. Thank you in advance.
The question is from Hyperskill.com as follows:
Write a program that reads five words from the standard input and outputs each word in a new line.
First, you need to print all the words from the first line, then from the second (from the left to right).
Sample Input 1:
This Java course
is adaptive
Sample Output 1:
This
Java
course
is
adaptive
My trial to solve it
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
/* I have not initialized the "userInput" String.
* I know that String is immutable in Java and
* if I initialize it to an empty String ""
* and read a String from user.
* It will not overwrite to the "userInput" String.
* But create another String object to give it the value of the user input,
* and references the new String object to "userInput".
* I didn't want to waste memory like that.
*/
String userInput;
String[] userInputSplitFirstLine = new String[3];
String[] userInputSplitSecondLine = new String[2];
Scanner scan = new Scanner(System.in);
userInput = scan.nextLine();
userInputSplitFirstLine = userInput.split("\\s+");
userInput = scan.nextLine();
userInputSplitSecondLine = userInput.split("\\s+");
for(String firstLineSplitted: userInputSplitFirstLine) {
System.out.println(firstLineSplitted);
}
for(String secondLineSplitted: userInputSplitSecondLine) {
System.out.println(secondLineSplitted);
}
scan.close();
}
}
If you try the sample input above, the output will match the sample output above. However, if you write more than 3 words to the first line and/or more than 2 words to the second line, the userInputSplitFirstLine array of size 3 will store more than 3 words. Same goes with the userInputSplitSecondLine array also. My first question is how can an array of size 3 (userInputSplitFirstLine) and an array of size 2 (userInputSplitSecondLine) can hold more than 3 and 2 elements, respectively? My second question is that how can I restrict/limit the number of words that the user can insert in a line; for example, the first line only accepts 3 words and the second line only accepts 2 words?
Also the answer to this question suggested by Hyperskill.com is as follows:
import java.util.Scanner;
class Main {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
String wordOne = scanner.next();
String wordTwo = scanner.next();
String wordThree = scanner.next();
String wordFour = scanner.next();
String wordFive = scanner.next();
System.out.println(wordOne);
System.out.println(wordTwo);
System.out.println(wordThree);
System.out.println(wordFour);
System.out.println(wordFive);
}
}

You can use next method of scanner object to read string and then it can be printed easily on new line.
while(true){
if(scanner.hasNext()){
System.out.println(scanner.next());
}
else{
break;
}
}

I think this should do the work. Don't hesitate to ask, if you have some questions.
import java.util.Scanner;
class App {
public static void main(String[] args) {
final StringBuffer line = new StringBuffer();
final StringBuffer words = new StringBuffer();
try (final Scanner sc = new Scanner(System.in)) {
while (sc.hasNextLine()) {
final String currentLine = sc.nextLine();
line.append(currentLine).append(System.lineSeparator());
for (final String word : currentLine.split("\\s+")) {
words.append(word).append(System.lineSeparator());
}
}
} finally {
System.out.println(line.toString());
System.out.println();
System.out.println(words.toString());
}
}
}

My first question is how can an array of size 3 (userInputSplitFirstLine) and an array of size 2 (userInputSplitSecondLine) can hold more than 3 and 2 elements, respectively?
The array here:
String[] userInputSplitFirstLine = new String[3];
is not the same one as the one you got from split:
userInputSplitFirstLine = userInput.split("\\s+");
When you do the above assignment, the old array that was in there is basically "overwritten", and now userInputSplitFirstLine refers to this new array that has a length independent of what the old array had. split always return a new array.
My second question is that how can I restrict/limit the number of words that the user can insert in a line; for example, the first line only accepts 3 words and the second line only accepts 2 words?
It really depends on what you mean by "restrict". If you just want to check if there are exactly three words, and if not, exit the program, you can do this:
userInputSplitFirstLine = userInput.split("\\s+");
if (userInputSplitFirstLine.length != 3) {
System.out.println("Please enter exactly 3 words!");
return;
}
You can do something similar with the second line.
If you want the user to be unable to type more than 3 words, then that's impossible, because this is a command line app.
By the way, the code in the suggested solution works because next() returns the next "word" (or what we generally think of as a word, anyway) by default.

hope this will help you!
public class pratice1 {
public static void main (String[]args) {
Scanner sc = new Scanner(System.in);
String input = sc.nextLine();
String input1 = sc.nextLine();
char[]a =input.toCharArray();
char[]a1 = input1.toCharArray();
System.out.println(input +""+ input1);
int a2=0;
if(input!=null) {
for(int i=0;i<input.length();i++) {
if(a[i]==' ') {
a2=i;
for(int j=0;j<a2;j++) {
System.out.println(a[i]);
a2=0;
}
}
else System.out.print(a[i]);
}System.out.println("");
for(int i=0;i<input1.length();i++) {
if(a1[i]==' ') {
a2=i;
for(int j=0;j<a2;j++) {
System.out.println(a1[i]);
a2=0;
}
}
else System.out.print(a1[i]);
}
}
}
}

To solve the problem:
Write a program that reads five words from the standard input and
outputs each word in a new line.
This was my solution:
while(scanner.hasNext()){
System.out.println(scanner.next());
}

Comma-Delimited String of Integers

This is the original prompt:
I need to write a program that gets a comma-delimited String of integers (e.g. “4,8,16,32,…”) from the user at the command line and then converts the String to an ArrayList of Integers (using the wrapper class) with each element containing one of the input integers in sequence. Finally, use a for loop to output the integers to the command line, each on a separate line.
This is the code that I have so far:
import java.util.Scanner;
import java.util.ArrayList;
public class Parser {
public static void main(String[] args) {
Scanner scnr = new Scanner(System.in);
ArrayList<String> myInts = new ArrayList<String>();
String integers = "";
System.out.print("Enter a list of delimited integers: ");
integers = scnr.nextLine();
for (int i = 0; i < myInts.size(); i++) {
integers = myInts.get(i);
myInts.add(integers);
System.out.println(myInts);
}
System.out.println(integers);
}
}
I am confused on where to go with the rest of this program. If someone could help explain to me what I need to do, that would be much appreciated!

As Matthew and Marc pointed out you have to first split the string into tokens and then parse each token to transform them into Integers.
You could try it with something like this:
String stringOfInts = "1,2,3,4,5";
List<Integer> integers = new ArrayList<>();
String[] splittedStringOfInts = stringOfInts.split(",");
for(String strInt : splittedStringOfInts) {
integers.add(Integer.parseInt(strInt));
}
// do something with integers
In the split() method you define how to split the string into tokens. In your case it's simply the comma (,) sign.
Hope this helps.
Regards Patrick

Java: Read a text file into an array

I've a txt file composed by two columns like this:
Name1 _ Opt1
Name2 _ Opt2
Name3 _ Opt3
In each row there's a name, a tab delimiter, a _ and then another name; there are really many rows (about 150000) and i'm not even sure which one is the best constructor to use, i'm thinking about a two dimensional array but it could be also something else if it's a better choice. For me it's important that i can access to the elements with something like this a[x][y].
I've done this but i just know how to count the number of the lines or how to put each lines in a different position of an array.
Here's the code:
int countLine = 0;
BufferedReader reader = new BufferedReader(new FileReader(filename));
while (true) {
String line = reader.readLine();
if (line == null) {
reader.close();
break;
} else {
countLine++;
}
}

Since you don't know the number of lines ahead of time, I would use an ArrayList instead of an array. The splitting of lines into String values can easily be done with a regular expression.
Pattern pattern = Pattern.compile("(.*)\t_\t(.*)");
List<String[]> list = new ArrayList<>();
int countLine = 0;
BufferedReader reader = new BufferedReader(new FileReader(filename));
while (true) {
String line = reader.readLine();
if (line == null) {
reader.close();
break;
} else {
Matcher matcher = pattern.matcher(line);
if (matcher.matches()) {
list.add(new String[] { matcher.group(1), matcher.group(2) });
}
countLine++;
}

The first thing you should do is to write a class that represents an entry in your file. It could be quite sophisticated but a really simple design will probably also do.
class Record {
final String name;
final String option;
Record(final String name, final String option) {
this.name = name;
this.option = option;
}
}
Using this class is much better than messing with arrays of strings.
The second thing to do is to use a more abstract data structure than an array structure to put your records into. This will free you from the burden of having to know the number of elements in advance. I recommend that you use an ArrayList for this. Then, you can read in one record at a time and add it to your collection.
List<Record> records = new ArrayList<Record>();
records.add(new Record("NameX", "OptionX"));
System.out.printf("There are %d records in the list.%n", records.size());
Of course, the second line in the above example should be done over and over again in your loop that reads the lines of the file.

Use ArrayList instead of array because the size is unknown. Use Scanner to read file, and to check existence of next line in file use hasNextLine() method,
import java.io.File;
import java.io.FileNotFoundException;
import java.util.ArrayList;
import java.util.Scanner;
class Test {
static Scanner userInput = new Scanner(System.in);
public static void main(String args[]) throws FileNotFoundException {
int countline = 0;
Scanner inp=new Scanner(new File("/home/nasir/Desktop/abc.txt"));
ArrayList<String> list=new ArrayList<String>();
while(inp.hasNextLine()){
list.add(inp.nextLine());// adding a row in ArrayList
countline++;// counting every line/row
}
System.out.println(countline+" "+list.get(2));
}// Main
}// Class

You can save the data on
HashMap>
The first String (key) is your name
The second String (key) is your opt and his value (reault) is the object result.
You can use it as:
result = youHashMap.get(name).get(opt);

String Arrays not returning expected value

I'm very new to Java but this has had me stumped for the last half an hour or so. I'm reading in lines from a text file and storing them as String Arrays. From here I'm trying to use the values from within the arrays to be used to initialise another class I have. To initialise my Route class (hence using routeName) I need to take the first value from the array and pass it as a string. When I try to return s[0] for routeName, I'm given the last line of from my text file. Any ideas on how to fix this would be greatly appreciated. I'm in the process of testing still so thats why my code is barely finished.
My text file is as follows.
66
Uq Lakes, Southbank
1,2,3,4,5
2,3,4,5,6
and my code:
import java.io.*;
import java.util.*;
public class Scan {
public static void main(String args[]) throws IOException {
String routeName = "";
String stationName = " ";
Scanner timetable = new Scanner(new File("fileName.txt"));
while (timetable.hasNextLine()) {
String[] s = timetable.nextLine().split("\n");
routeName = s[0];
}
System.out.println(routeName);
}
}

The method you are calling timetable.nextLine.split("\n") will return the Array of String.
So every time when you call this method is overwrites your array with new line in file and as the last line is added finally in your array you are getting the lat line at the end.
below is the code you can use.
public static void main(String[] args) throws FileNotFoundException {
String routeName = "";
Scanner timetable;
int count = 0;
String[] s = new String[10];
timetable = new Scanner(new File("fileName.txt"));
while (timetable.hasNextLine()) {
String line = timetable.nextLine();
s[count++] = line;
}
routeName = s[0];
System.out.println(routeName);
}

Scanner.nextLine() returns a single line so splitting by '\n' will always give a single element array, e.g.:
timetable.nextLine().split("\n"); // e.g., "1,2,3,4,5" => ["1,2,3,4,5"]
Try splitting by the ',' instead, e.g.:
timetable.nextLine().split(","); // e.g., "1,2,3,4,5" => ["1", "2", "3", "4", "5"]
NOTE: If you are intending for the array to contain individual lines, then check out this SO post.
Scanner s = new Scanner(new File(filename));
List<String> lines = new ArrayList<String>(); // A List can be dynamically resized
while(s.hasNextLine()) lines.add(s.nextLine()); // Store each line in the list
String[] arr = lines.toArray(new String[0]); // If you really need an Array, use this

Your while loop itterates over all lines and sets the current line to the routeName. Thats why you habe the last line in you string. What you could do is calling a break, when you habe read the first line oft the file. Then you will have the first line.

Reading two lines from an input file using Scanner

Hi I'm in a programming class over the summer and am required to create a program that reads input from a file. The input file includes DNA sequences ATCGAGG etc and the first line in the file states how many pairs of sequences need to be compared. The rest are pairs of sequences. In class we use the Scanner method to input lines from a file, (I read about bufferedReader but we have not covered it in class so not to familiar with it) but am lost on how to write the code on how to compare two lines from the Scanner method simultaneously.
My attempt:
public static void main (String [] args) throws IOException
{
File inFile = new File ("dna.txt");
Scanner sc = new Scanner (inFile);
while (sc.hasNextLine())
{
int pairs = sc.nextLine();
String DNA1 = sc.nextLine();
String DNA2 = sc.nextLine();
comparison(DNA1,DNA2);
}
sc.close();
}
Where the comparison method would take a pair of sequences and output if they had common any common characters. Also how would I proceed to input the next pair, any insight would be helpful.. Just stumped and google confused me even further. Thanks!
EDIT:
Here's the sample input
7
atgcatgcatgc
AtgcgAtgc
GGcaAtt
ggcaatt
GcT
gatt
aaaaaGTCAcccctccccc
GTCAaaaaccccgccccc
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
gctagtacACCT
gctattacGcct

First why you are doing:
while (sc.hasNextLine())
{
int pairs = sc.nextLine();
While you have pairs only in one line not pairs and two lines of input, but number of lines once? Move reading pairs from that while looop and parse it to int, then it does not matter but you could use it to stop reading lines if you know how many lines are there.
Second:
throws IOException
Might be irrelevant but, really you don't know how to do try catch and let's say skip if you do not care about exceptions?
Comparision, if you read strings then string has method "equals" with which you can compare two strings.
Google will not help you with those problems, you just don't know it all, but if you want to know then search for basic stuff like type in google "string comparision java" and do not think that you can find solution typing "Reading two lines from an input file using Scanner" into google, you have to go step by step and cut problem into smaller pieces, that is the way software devs are doing it.
Ok I have progz that somehow wokrked for me, just finds the lines that have something and then prints them out even if I have part, so it is brute force which is ok for such thing:
import java.io.File;
import java.io.IOException;
import java.util.Scanner;
public class program
{
public static void main (String [] args) throws IOException
{
File inFile = new File ("c:\\dna.txt");
Scanner sc = new Scanner (inFile);
int pairs = Integer.parseInt(sc.nextLine());
for (int i = 0; i< pairs-1; i++)
{
//ok we have 7 pairs so we do not compare everything that is one under another
String DNA1 = sc.nextLine();
String DNA2 = sc.nextLine();
Boolean compareResult = comparison(DNA1,DNA2);
if (compareResult){
System.out.println("found the match in:" + DNA1 + " and " + DNA2) ;
}
}
sc.close();
}
public static Boolean comparison(String dna1, String dna2){
Boolean contains = false;
for (int i = 0; i< dna1.length(); i++)
{
if (dna2.contains(dna1.subSequence(0, i)))
{
contains = true;
break;
}
if (dna2.contains(dna1.subSequence(dna1.length()-i,dna1.length()-1 )))
{
contains = true;
break;
}
}
return contains;
}
}