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Scanning a file and getting two tokens at a time and saving those in an ArrayList

Hi everyone this is my first question here so I apologize in advance if it is not in the correct format for this forum. I'm a comp sci student and I am really a novice programmer. For an assignment, I need to read in a file of polynomials and then sort them from highest degree to lowest. On each line of the file I have a coefficient and an exponent separated by a space.
This is what my .txt file looks like:
"5.6 3
4 1
8.3 0" which represents the polynomial 5.6x^3 + 4x + 8.3
I have to scan the file from a JFileChooser and then add the tokens to an ArrayList of type Polynomial. My question/problem is how can I run the file contents through a for loop and separate the first token(coefficients) from the second token(exponents) and then add them to the ArrayList? I'm going to need the exponents to be of type int and the coefficients should be double.
This is what I have so far:
ArrayList aList = new ArrayList();
// scanner used to read each line
try {
scan = new Scanner(file);
if (file.isFile()) {
while (scan.hasNext()) {
for (int i = 0; i < something.size(); i++) {
//this is where I'm lost, not sure what I need to do here
}
}
}
....
Thank you guys I appreciate the assistance.
-Linden
EDIT:
Alright I figured it out, it was a lot more complicated than I thought. Here's what I did:
Scanner scan = new Scanner(file);
if (file.isFile()) {
for (int i = 0; i <=2; i ++) {
term(scan);
}
}
static void term(Scanner scan) {
String s = scan.nextLine();
String [] splitter = s.split(" ");
String coefficient = splitter[0];
String exponent = splitter[1];
//populating
try {
arrayList.add(new Polynomial(coefficient, exponent));
} catch (InvalidPolynomialSyntax e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
Thanks to the two guys that tried to help me out and the 24 viewers who didn't lol

First, you need to look at the scanner class. What methods does it have that you should use to get the data you need?
I don't want to give you the answer to your homework out of respect but broadly what you need is a way to get each line of that file from the scanner so you can compare the contents of each line to each other.
So look at the scanner class documentation and see what it has that you can use.
Start by simply trying to print out each line. Once you do that you can think about how you want to compare them.

you can read file as one sentence. First get all the text such as 5.6 3 4 1 8.3 0 as string. Then you can just use String [] arrayOfNumbers = yourString.split(" ");
This will split the string according to " " character so you get numbers directly.

Am I overcomplicating a simple solution in Java?

For my Java homework I need to create a script that returns the first word within a string, and, as a part two, I need to also return the second word. I'm currently working on the first part, and I think I'm close, but I'm also wondering if I am over complicating my code a bit.
public static void statements(){
Scanner userInput = new Scanner(System.in);
char [] sentenceArray;
String userSentence;
char sentenceResult;
System.out.print("Enter a complete sentence: ");
userSentence = userInput.nextLine();
for(int x = 0; x < userSentence.length(); x++){
sentenceResult = userSentence.charAt(x);
sentenceArray = new char[userSentence.length()];
sentenceArray[x] = sentenceResult;
if(sentenceArray[x] != ' '){
System.out.print(sentenceArray[x]);
//break; This stops the code at the first letter due to != ' '
}
}
}
I think I've nearly got it. All I need to get working, for the moment, is the for loop to exit once it recognizes there is a space, but it prints out the entire message regardless. I'm just curious if this can be done a little simpler, as well as maybe a hint of what I could do instead, or how to finish.
Edit: I was able to get the assignment completed by using the split method. This is what it now looks like
public static void statements(){
Scanner userInput = new Scanner(System.in);
String userSentence;
System.out.print("Enter a complete sentence: ");
userSentence = userInput.nextLine();
String [] sentenceArray = userSentence.split(" ");
System.out.println(sentenceArray[0]);
System.out.println(sentenceArray[1]);
}
}

As it is your homework, I would feel bad to give you code and resolve it for you.
Seems like you really overcomplicated that, and you are aware, so it's good sign.
I need to create a script that returns the first word within a string,
and, as a part two, I need to also return the second word
So, you have a String object, then check yourself the methods of that class.
It is possible to solve it in 2 lines of code, but:
you must be aware of one special method of String class, the most useful will be one that could somehow split the string for you
you need to have some knowledge about java regular expressions - words are separated by space
after you split the string, you should get an array, accessing first and second element by index of an array will be sufficient

Personally, I think you are overthinking it. Why not read in the whole line and split the string by whitespaces? This isn't a complete solution, just a suggestion for how you can get the words.
public static void main(String[] args) {
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
System.out.print("Enter a complete sentence: ");
try {
String userSentence = reader.readLine();
String[] words = userSentence.split(" ");
System.out.println(words[0]);
System.out.println(words[1]);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

Here's how I'd do it. Why not return all the words?
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
/**
* Add something descriptive here.
* User: MDUFFY
* Date: 8/31/2017
* Time: 4:58 PM
* #link https://stackoverflow.com/questions/45989774/am-i-over-complicating-a-simple-solution
*/
public class WordSplitter {
public static void main(String[] args) {
for (String arg : args) {
System.out.println(String.format("Sentence: %s", arg));
List<String> words = getWords(arg);
System.out.println(String.format("# words : %d", words.size()));
System.out.println(String.format("words : %s", words));
}
}
public static List<String> getWords(String sentence) {
List<String> words = new ArrayList<>();
if ((sentence != null) && !"".equalsIgnoreCase(sentence.trim())) {
sentence = sentence.replaceAll("[.!?\\-,]", "");
String [] tokens = sentence.split("\\s+");
words = Arrays.asList(tokens);
}
return words;
}
}
When I run it with this input on the command line:
"The quick, agile, beautiful fox jumped over the lazy, fat, slow dog!"
Here's the result I get:
Sentence: The quick, agile, beautiful fox jumped over the lazy, fat, slow dog!
# words : 12
words : [The, quick, agile, beautiful, fox, jumped, over, the, lazy, fat, slow, dog]
Process finished with exit code 0

JAVA: How to convert String ArrayList to Integer Arraylist?

My question is -
how to convert a String ArrayList to an Integer ArrayList?
I have numbers with ° behind them EX: 352°. If I put those into an Integer ArrayList, it won't recognize the numbers. To solve this, I put them into a String ArrayList and then they are recognized.
I want to convert that String Arraylist back to an Integer Arraylist. So how would I achieve that?
This is my code I have so far. I want to convert ArrayString to an Int Arraylist.
// Read text in txt file.
Scanner ReadFile = new Scanner(new File("F:\\test.txt"));
// Creates an arraylist named ArrayString
ArrayList<String> ArrayString = new ArrayList<String>();
// This will add the text of the txt file to the arraylist.
while (ReadFile.hasNextLine()) {
ArrayString.add(ReadFile.nextLine());
}
ReadFile.close();
// Displays the arraystring.
System.out.println(ArrayString);
Thanks in advance
Diego
PS: Sorry if I am not completely clear, but English isn't my main language. Also I am pretty new to Java.

You can replace any character you want to ignore (in this case °) using String.replaceAll:
"somestring°".replaceAll("°",""); // gives "sometring"
Or you could remove the last character using String.substring:
"somestring°".substring(0, "somestring".length() - 1); // gives "somestring"
One of those should work for your case.
Now all that's left is to parse the input on-the-fly using Integer.parseInt:
ArrayList<Integer> arrayInts = new ArrayList<Integer>();
while (ReadFile.hasNextLine()) {
String input = ReadFile.nextLine();
try {
// try and parse a number from the input. Removes trailing `°`
arrayInts.add(Integer.parseInt(input.replaceAll("°","")));
} catch (NumberFormatException nfe){
System.err.println("'" + input + "' is not a number!");
}
}
You can add your own handling to the case where the input is not an actual number.

For a more lenient parsing process, you might consider using a regular expression.
Note: The following code is using Java 7 features (try-with-resources and diamond operator) to simplify the code while illustrating good coding practices (closing the Scanner). It also uses common naming convention of variables starting with lower-case, but you may of course use any convention you want).
This code is using an inline string instead of a file for two reasons: It shows that data being processed, and it can run as-is for testing.
public static void main(String[] args) {
String testdata = "55°\r\n" +
"bad line with no number\r\n" +
"Two numbers: 123 $78\r\n";
ArrayList<Integer> arrayInt = new ArrayList<>();
try (Scanner readFile = new Scanner(testdata)) {
Pattern digitsPattern = Pattern.compile("(\\d+)");
while (readFile.hasNextLine()) {
Matcher m = digitsPattern.matcher(readFile.nextLine());
while (m.find())
arrayInt.add(Integer.valueOf(m.group(1)));
}
}
System.out.println(arrayInt);
}
This will print:
[55, 123, 78]

You would have to create a new instance of an ArrayList typed with the Integer wrapper class and give it the same size buffer as the String list:
List<Integer> myList = new ArrayList<>(ArrayString.size());
And then iterate through Arraystring assigning the values over from one to the other by using a parsing method in the wrapper class
for (int i = 0; i < ArrayString.size(); i++) {
myList.add(Integer.parseInt(ArrayString.get(i)));
}

How to take integer and remove other data types from the file java?

I do not know how to take the integer and ignore the strings from the file using scanner. This is what I have so far. I need to know how to read the file token by token. Yes, this is a homework problem. Thank you so much.
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;
public class ClientMergeAndSort{
public static void main(String[] args){
int length = 13;
try{
Scanner input = new Scanner(System.in);
System.out.print("Enter the file name with extention : ");
File file = new File(input.nextLine());
input = new Scanner(file);
while (!input.hasNextInt()) {
input.next();
}
int[] arraylist = new int[length];
for(int i =0; i < length; i++){
length++;
arraylist[i] = input.nextInt();
System.out.print(arraylist[i] + " ");
}
} catch (Exception ex) {
ex.printStackTrace();
}
}
}

Take a look at the API for what you're doing.
http://docs.oracle.com/javase/7/docs/api/java/util/Scanner.html#hasNextInt()
Specifically, Scanner.hasNextInt().
"Returns true if the next token in this scanner's input can be interpreted as an int value in the default radix using the nextInt() method. The scanner does not advance past any input."
So, your code:
while (!input.hasNextInt()) {
input.next();
}
That's going to look and see if input hasNextInt().
So if the next token - one character - is an int, it's false, and skips that loop.
If the next token isn't an int, it goes into the loop... and iterates to the next character.
That's going to either:
- find the first number in the input, and stop.
- go to the end of the input, not find any numbers, and probably hits an IllegalStateException when you try to keep going.
Write down in words what you want to do here.
Use the API docs to figure out how the hell to tell the computer that. :) Get one bit at a time right; this has several different parts, and the first one doesn't work yet.
Example: just get it to read a file, and display each line first. That lets you do debugging; it lets you build one thing at a time, and once you know that thing works, you build one more part on it.
Read the file first. Then display it as you read it, so you know it works.
Then worry about if it has numbers or not.

A easy way to do this is read all the data from file in a way that you prefer (line by line for example) and if you need to take tokens, you can use split function (String.split see Java doc) or StringTokenizer for each line of String that you are reading using a loop, in order to create tokens with a specific delimiter (a space for example) so now you have the tokens and you can do something that you need with them, hope you can resolve, if you have question you can ask.
Have a nice programming.

import static java.nio.file.Files.readAllBytes;
import static java.nio.file.Paths.get;
import java.io.IOException;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class Test {
public static void main(String args[]) throws IOException {
String newStr=new String(readAllBytes(get("data.txt")));
Pattern p = Pattern.compile("-?\\d+");
Matcher m = p.matcher(newStr);
while (m.find()) {
System.out.println("- "+m.group());
}
}
}
This code fill read the file and then using the regular expression you can get only Integer values.
Note: This code works in Java 8

I Think This will work for you requirement.
Before reading the data from the file initially,try to write some content to the file by using scanner and filewriter then try to execute the below code snippet.
File file = new File(your filepath);
List<Integer> list = new ArrayList<Integer>();
try {
BufferedReader bufferedReader = new BufferedReader(new FileReader(file));
String str =null;
while(true) {
str = bufferedReader.readLine();
if(str!=null) {
System.out.println(str);
char[] chars = str.toCharArray();
String finalInt = "";
for(int i=0;i<chars.length;i++) {
if(Character.isDigit(chars[i])) {
finalInt=finalInt+chars[i];
}
}
list.add(Integer.parseInt(finalInt));
System.out.println(list.size());
System.out.println(list);
} else {
break;
}
}
}catch (Exception e) {
// TODO: handle exception
e.printStackTrace();
}
The final println statement will display all the integer in your file line by line.
Thanks

Read words until user writes 'end', then, order lexicographically(as in a dictionary), show the last word

User will enter words until the last word written is "end", then the code has to order lexicographically, as we have in a dictionary, all the words entered before 'end' and print the last word, the one classified the last.
//.....
Scanner word = new Scanner (System.in);
String keyword="end";
String finalstring;
String[] firststring= new String[1000]; //Don't know how to stablish a //dynamic string[] length, letting the user stablish the string[].length
for(int c=0;c<firststring.length;c++){
firststring[c]=word.next();
if(firststring[c].equals(keyword)){
finalstring=firststring[c].substring(0,c);
c=cadena.length-1; //To jump out of the for.
}
}
for (int c=0;c<finalstring.length();c++) {
for(int i=c+1;i<finalstring.length();i++) {
if (firststring[c].compareTo(firststring[i])>0) {
String change = firststring[c];
firststring[c] = firststring[i];
firststring[i] = change;
}
}
}
System.out.print("\nYou entered "end" and the last word classified is "+finalstring[finalstring.length()-1]); //Of course, error here, just did it to put one System.out.print of how should the result be.
}
}
This is what I tried, though, without any type of success, any help of yours will be a big help, thank you ALL!

Don't know how to stablish a dynamic string[] length, letting the user establish the string[].length
It is not necessary to do that. But here's how.
Approach #1: ask the user to give you a number and then allocate the array like this:
String[] strings = new String[theNumber];
Warning: the requirements don't say you are allowed to do that, and you may lose marks for deviating from the requirements.
Approach #2: use an ArrayList to accumulate a list of words, the use List.toArray to create an array from the list contents. (Read the javadocs for list to work it out.)
Of course, error here, just did it to put one System.out.print of how should the result be.
Yea. One problem is that the length is 1000, but you don't have 1000 actual strings in the array. The same problem affects your earlier code too. Think about is ...
I'm not going to fix your code to make it work. I've given you enough hints for you to do that for yourself. If you are prepared to put in the effort.
One more hint: you can / should use break to break out of the first loop.

I know some words are not in English but in Catalan, but the code can be perfectly understood, yesterday I finally programmed this answer:
public static void main(String[] args) {
Scanner entrada= new Scanner(System.in);
System.out.println("Escriu les paraules que vulguis, per acabar, usa la paraula 'fi'.");
String paraules = "";
int c=0;
do {
String paraula = entrada.next();
if (paraula.equals("fi")) {
c++;
} else {
if (paraula.compareTo(paraules) > 0) {
paraules = paraula;
}
}
} while (c==0);
System.out.println("L'última parala ordenada alfabèticament és "+paraules+".\n");
}
}