Develop Reference

Sudoku Code Program - Checking Rows,Columns, and Boxes

I need help checking rows, columns, and boxes for a Sudoku program. I am a high school student that needs help completing this project. If any one could provide help that would be awesome! I am currently working on checking boxes where I have a comment saying "Start Here". Thanks!
import java.util.*;
public class Run
{
Scanner scanner = new Scanner(System.in);
public static void main(String[] args)
{
char [][] board = new char [9][9];
Scanner scanner = new Scanner(System.in);
System.out.println("Welcome to Sudoku!\n");
fill(board);
printBoard(board);
inputLengthandDigits(board);
System.out.println();
printBoard(board);
}
public static void fill(char[][] arr){
for(int row = 0; row < arr.length; row++){
for(int col= 0; col< arr[row].length; col++){
arr[row][col] = '-';
}
}
}
public static void printBoard(char [][] array)
{
for(char[] row: array)
{
for(char play: row)
{
System.out.print(play+ " ");
}
System.out.println();
}
}
public static void inputLengthandDigits(char[][] array){
Scanner in = new Scanner(System.in);
for (int i = 0; i < 9; i++)
{
System.out.println("\nEnter the numbers in row " + (i+1) + ":");
String input = in.nextLine();
String numbers = "123456789-";
boolean numberscheck = false;
boolean endCheck = true;
boolean onlyOnce = true;
//Input Validation Starts Here!
//Checks if Input is only digits 0-9
do{
if(endCheck==false){
System.out.println("\nPlease input numbers only (1-9)!");
input = in.nextLine();
}
if(onlyOnce==false){
System.out.println("\nPlease input numbers only once!");
input = in.nextLine();
}
//Checks Length of User Input
while(input.length() < 9 || input.length() > 9){
System.out.println("\nPlease input 9 numbers!");
input = in.nextLine();
}
//Start Here
for(int a = 0; a<input.length()-1; a++){
for(int b= a + 1; b<input.length(); b++){
if(input.charAt(a)==input.charAt(b)){
onlyOnce = false;
}
}
}
for(int x = 0; x < input.length(); x++){
char thing = input.charAt(x);
numberscheck = false;
for(int y = 0; y < numbers.length(); y++){
char numbersn = numbers.charAt(y);
if(thing == numbersn){
numberscheck = true;
endCheck = true;
break;
}
}
if(numberscheck == false){
endCheck = false;
break;
}
}
}while(endCheck==false || onlyOnce==false);
for(int j=0; j<9; j++){
array[i][j] = input.charAt(j);
}
}
}
}

My initial response is too long for a comment. I'm not sure I have a solution to your problem, largely because you haven't actually pointed out which bit is a problem yet, but these pointers should help improve things anyway:
Please reformat your code. It is actually quite painful to look at. Spaces should be used consistently around variables, key words, brackets and operands. Opening curly braces should be on the same line as the method signature, for() loop or whatever else comes first. You have random blank lines within methods which don't separate logical sections so are just confusing. The compiler won't care about any of this, but if you can make your code look neater people will instinctively presume you care and are more likely to credit you with the ability to write decent code.
You have declared a new scanner variable three times. This is redundant and wasteful clutter. Either have a single, class-wide scanner, or (preferably), only create a scanner in a method which actually uses it and then remember to call scanner.close() once the scanner is no longer required.
inputLengthandDigits is a weird name. Is 'Lengthand' a single word, or should it be 'inputLengtHandDigits' or 'inputLengthAndDigits'? In camel case, capitalise every word except the first to make the whole easier to read. Whatever it should be, I don't understand from the name what this method does. It isn't inputting anything, it's getting inputs from someone else. Perhaps getData or populateGrid might be more explanatory.
9 appears quite a few times, with no explanation. I know where it came from, because I spend far too much time playing Sudoku, but it is a magic number and these are to be avoided at all costs. I met a magic number in the workplace once, wasted half a day trying to do what could have been a ten minute job if colleagues had recorded what the number was and where it came from. Here, just have a private static final int maxNumber = 9; statement.
A good thing: your main() method has almost no fiddly details in it. You have effectively used method calls to tell a story and describe what is happening elsewhere. This is a really, really good thing to do :)
Some of your logic tests can be tidied up a bit, e.g. !onlyOnce is the same as onlyOnce == false, and input.length() < maxNumber || input.length() > maxNumber can be simplified to input.length() != maxNumber. It's exactly the same logic, but faster to type and easier to read :)
It looks like your code under the //Start here comment is checking that you don't have any duplicate numbers. If you do get duplicate numbers, the program is still going to try and run the next bit of code before asking the user for alternative input. Is that something you want to happen, or a waste of time?
I actually burst out laughing when I saw a variable called 'thing'. Please, find a name which actually describes the purpose of this variable.
I have now run the code, and it rightly pointed out an error when I tried to key in duplicate numbers for row 4. However, it's now stuck there and keeps asking me to try again even when I put in a valid set of digits. This needs to be fixed. Look closely at which flags are triggering the request to retry. Run your code in debugging mode (you are using an IDE like IntelliJ or Eclipse, aren't you?) and deliberately enter a bad row to see the behaviour for yourself and where the logic is going wrong.
This whole method to get the row input, validate it, and then populate the array, is very big and confusing. You need to refactor it into a lot of smaller methods. Here is a suggestion to play with:
private static char[][] populateGrid(char[][] array) {
Scanner scanner = new Scanner(System.in);
for (int i = 0; i <maxNumber; i++) {
String rowData = getRowInput(scanner);
populateRow(array, rowNumber, rowData);
}
scanner.close;
return array;
}
private static String getRowInput(Scanner scanner) {
System.out.println("\nEnter the numbers in row " + (i + 1) + ":");
String input = scanner.nextLine();
while (!isValidInput(input) {
System.out.println("Please enter only the digits 1-9 in any order, with no duplicates or omissions");
input = scanner.nextLine();
}
return input;
}
private static boolean isValidInput(String input) {
if (!rightLengthOfInput(input)) {
return false;
}
if (!allUniqueDigits(input)) {
return false;
}
if (!usesCorrectCharacters(input)) {
return false;
}
return true;
}
I'll leave you to make the different input validation methods. It will largely be a case of moving your existing code, but the method names will help humans understand what each section is doing. This structure also allows you to cleanly add more validation checks, should such a thing be desired in the future.
Things to consider after all that:
Are you going to check that you have a viable Sudoku solution, or will you trust the user to put in correct data such that the columns also have each of the nine digits in them? How will you handle an invalid grid, e.g. each row is identical?
How far does this assignment want you to go? Do you need to systematically remove numbers to get a solvable puzzle rather than a completed grid? Will the assignment stop at a puzzle which can be seen in the console, or do you need a printable format, or will the user be able to play through the program? If the latter option, will this be in the console or using a graphical interface?
I appreciate that there is a lot to think about and work on here. Take it steadily, one step at a time, and keep asking questions if you need too.

A method that I wrote with a scanner class doesn't seem to end

I wrote a method in order to get the choice of the user for the size of a grid. However, my code doesn't seem to work after executing the method, as it continues to run without end after I type in the response to console (if it matters, I am on repl.it). What is the issue with the code that prevents it from ending?
public static String createSize() {
int count = 0;
String answer = "";
Scanner sc = new Scanner(System.in);
System.out.println("How big do you want the grid? (Sizes: 4x4, 5x5, 6x6)");
String size = sc.nextLine();
//Checks if user-inputted answer matches possible answers
while (count < 1) {
if (size.equals("4x4") || size.equals("5x5") || size.equals("6x6")) {
count++;
answer = sc.nextLine();
}
else {
System.out.println("That was not a viable size. Please type a viable size.");
size = sc.nextLine();
}
}
sc.close();
return answer;
}

In the first If check in the while loop
Change
answer = sc.nextLine();
to
answer = size;
since u do not want the user to input size twice.
Your code should work fine now.
Let me know if anything isn't clear so I can modify and elaborate further

what's the main problem? I tried to run this code on all possible test cases and I didn't get any problem.

In the if statement you have answer = sc.nextLine(); which will again ask you for the input that's why the program was not executing further. If you pass input second time only then it will execute. Further in if statement answer wasn't assigned any value so even after entering two values it will not return anything.
Correction :-
if (size.equals("4x4") || size.equals("5x5") || size.equals("6x6")) {
count++;
answer = size;
}

Stuck While Loop (Java)

all!
I'm a university freshman computer science major taking a programming course. While doing a homework question, I got stuck on a certain part of my code. Please be kind, as this is my first semester and we've only been doing Java for 3 weeks.
For context, my assignment is:
"Create a program that will ask the user to enter their name and to enter the number of steps they walked in a day. Then ask them if they want to continue. If the answer is "yes" ask them to enter another number of steps walked. Ask them again if they want to continue. If they type anything besides "yes" you should end the program by telling them "goodbye, [NAME]" and the sum of the number of steps that they have entered."
For the life of me, I can not get the while loop to end. It's ignoring the condition that I (probably in an incorrect way) set.
Can you please help me and tell me what I'm doing wrong?
import java.util.Scanner;
public class StepCounter
{
/**
* #param args the command line arguments
*/
public static void main(String[] args)
{
final String SENTINEL = "No";
String userName = "";
String moreNum = "";
int numStep = 0;
int totalStep = 0;
boolean done = false;
Scanner in = new Scanner(System.in);
Scanner in2 = new Scanner(System.in);
// Prompt for the user's name
System.out.print("Please enter your name: ");
userName = in.nextLine();
while(!done)
{
// Prompt for the number of steps taken
System.out.print("Please enter the number of steps you have taken: ");
// Read the value for the number of steps
numStep = in.nextInt();
// Prompt the user if they want to continue
System.out.print("Would you like to continue? Type Yes/No: ");
// Read if they want to continue
moreNum = in2.nextLine();
// Check for the Sentinel
if(moreNum != SENTINEL)
{
// add the running total of steps to the new value of steps
totalStep += numStep;
}
else
{
done = true;
// display results
System.out.println("Goodbye, " + userName + ". The total number of steps you entered is + " + totalStep + ".");
}
}
}
}

To compare the contents of String objects you should use compareTo function.
moreNum.compareTo(SENTINEL) return 0 if they are equal.
== operator is used to check whether they are referring to same object or not.
one more issue with addition of steps, addition should be done in case of "No" entered also

Use
if(!moreNum.equals(SENTINEL))
Instead of
if(moreNum != SENTINEL)
Also, make sure to add: totalStep += numStep; into your else statement so your program will actually add the steps together.

Matching user input against a string array in java?

I am incredibly new to java and have been given the following task:
Write a Java Program to prompt a user for a 3 letter body part name which has to be in the 'official' list of 3 letter body parts. (Arm, Ear, Eye, Gum, Hip, Jaw, Leg, Lip, Rib, Toe)
If a user makes a guess correctly then display the correct guess as part of a list.
Allow the user to keep guessing until they have all 10.
If a body part is incorrect then display an appropriate message.
Display the number of guesses they have made including
the correct ones.
The advice given was to use Arrays and Collections as well as Exception Handling where appropriate but I don't know where to go from what I've coded so far. Any help would be appreciated so much, thank you.
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
String[] bodyparts = new String [10];
bodyparts[0] = "Arm";
bodyparts[1] = "Ear";
bodyparts[2] = "Eye";
bodyparts[3] = "Gum";
bodyparts[4] = "Hip";
bodyparts[5] = "Jaw";
bodyparts[6] = "Leg";
bodyparts[7] = "Lip";
bodyparts[8] = "Rib";
bodyparts[9] = "Toe";
Set<String> bodypartSet = new TreeSet<>();
Collections.addAll(bodypartSet, bodyparts);
System.out.println("Please enter a 3 letter body part: ");
String bodypart = input.nextLine();
if (bodypartSet.contains(bodypart)) {
System.out.println("Correct, " + bodypart + " is on the list!");
} else {
System.out.println("Nope, try again!");
}
}

There are a lot of way to do this. The following, isn't the best or the most efficient, but it should work...
First of all, you have to put your "official" list in a structure, like an array:
private static String[] offList={Arm, Ear, Eye, Gum, Hip, Jaw, Leg, Lip, Rib, Toe};
Now you have to write a method that can find a world in that "offList", like that:
private static boolean find(String word){
for( int i=0; i<offList.length; i++){
if(word.equals(offList[i])) //if "word" is in offList
return true;
}
return false;
}
Now, let's create this guessing game GUI:
public static void main(String[] args){
LinkedList<String> guessed=new LinkedList<>();
String s;
Scanner input = new Scanner(System.in);
while(guessed.size()<offList.length){
System.out.println("Guessed= "+guessed.toString()); //you have to change it, if you want a better look
System.out.print("Try:");
s=input.nextLine();
/*Here we ask to the user the same thing, unless the guessed list
contains all the words of offList.
Every time we print the guessed worlds list*/
if(find(s)){
System.out.println("This world is in offList!");
if(!guessed.contains(s)) //the world is counted only one time!
guessed.add(s);
}else
System.out.println("Sorry...");
}
System.out.println("The complete list is "+guessed.toString());
}
If you want to show this game in a window, you should have to study some Java Swing classes.
EDIT: I post my answer before the main post editing. First of all you have to understand the Collections advantages and usage... When you know all the LinkedList methods, for example, this assignment looks like a joke! ;)

You need a loop for that, otherwise it will only ask for input once.
Something like this should do:
ArrayList<String> bodyParts = new ArrayList<String>();
bodyParts.add("Arm");
bodyParts.add("Ear");
bodyParts.add("Eye");
bodyParts.add("Gum");
bodyParts.add("Hip");
bodyParts.add("Jaw");
bodyParts.add("Leg");
bodyParts.add("Lip");
bodyParts.add("Rib");
bodyParts.add("Toe");
String input = "";
int totalGuesses = 0;
Scanner sc = new Scanner(System.in);
System.out.println("Start guessing...");
while (!bodyParts.isEmpty()) {
totalGuesses++;
input = sc.nextLine();
if (input.length() != 3 || !bodyParts.contains(input)) {
// incorrect, do nothing
System.out.println("Nope.");
} else {
// correct, remove entry
bodyParts.remove(input);
System.out.println("Correct! " + (10 - bodyParts.size()) + " correct guess" + ((10 - bodyParts.size()) != 1 ? "es" : ""));
}
}
System.out.println("Done. You have found them all after " + totalGuesses + " guesses.");
sc.close();
Also, this is case sensitive. It will not find Arm when typing arm. And if you need the number of all guesses you can simply add an int before the loop and increase it inside.
The result of my example:
Start guessing...
arm
Nope.
Arm
Correct! 1 correct guess
Arm
Nope.
Ear
Correct! 2 correct guesses
Eye
Correct! 3 correct guesses
(...)
Rib
Correct! 9 correct guesses
Toe
Correct! 10 correct guesses
Done. You have found them all after 12 guesses.

Asking user input for an integer in java

I'm doing a basic java tutorial that is basically a mad libs program. The idea came up in the tutorial to try making sure a user is at least 13, but the example hard coded the age into the program. I wanted to try getting the age from the user, but at this point, my code gives me an error because a "string cannot be converted to an integer." Looking at my code, I don't see why it's giving me this error. Here is what I used:
int age = console.readLine("Enter your age: ");
if (age < 13) {
//enter exit code
console.printf("Sorry but you must be at least 13 to use this program.\n");
System.exit(0);
}
I have looked for other answers, but I didn't see any that I could discern from the specific problems they were trying to fix.

You should use
try{
int age = Integer.parseInt(console.readLine("Enter your age: "));
// do stuff
} catch (NumberFormatException e) {
// User did not enter a number
}
Java doesn't cast between the two automatically. The above method however will throw an exception when you don't enter a number which you will have to handle

You can use
Scanner input = new Scanner(System.in);
int Age = input.nextInt();
input.nextLine();

Okay, I'm not sure if it's cool to answer your own question. I managed to get this to work, so in case someone else encounters the same problem. Here is the code that I used:
String ageAsString = console.readLine("Enter your age: ");
int age = Integer.parseInt(ageAsString);
if (age < 13) {
//enter exit code
console.printf("Sorry but you must be at least 13 to use this program.\n");
System.exit(0);
}