We Keep Coding

Accepting string inputs into an array and checking the availability of the string in the array

So I am completely new to java, and I want to create a code to accept string inputs from a user, and store it into an array. After this in the next statement, I will type a value into the terminal, and I want the code to compare my string input to one of the strings in the array and print available on the terminal when the string is available and vice versa. The first part of my code was right (hopefully) but I had a problem in comparing the strings. I feel it doesn't check the strings with my input in the code. Here is my code, Could anyone please help me with this? Thank you so much.
import java.util.Scanner;
class Course {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
String a[] = new String[20] //assuming max 20 strings
System.out.println("Enter no. of courses");
int no_of_courses = sc.nextInt(); // number of strings
if (no_of_courses <= 0)
System.out.println("Invalid Range");
else {
System.out.println("Enter course names:");
for (int i = 0; i < no_of_courses; i++) {
a[i] = sc.next(); //accepting string inputs
}
System.out.println("Enter the course to be searched:");
String search = sc.next() //entering a string to search
for (int i = 0; i < no_of_courses; i++) {
if (a[i].equals(search)) //I feel the problem is here
System.out.println(search + "course is available");
break;
else
System.out.println(search + "course is not available");
}
}
}
}
I expect the output to be
<string> course is available
when my string matches a string in the array and
<string> course is not available
when my entered string doesn't match a string in the array
But there is no output :(

I have modified your code and commented on line where it need to be explained. check it carefully.
import java.util.Scanner;
class Course {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.println("Enter no. of courses");
int no_of_courses = sc.nextInt(); // number of strings
String a[] = new String[no_of_courses]; // do not assume when you have proper data.
if (no_of_courses <= 0)
System.out.println("Invalid Range");
else {
System.out.println("Enter course names:");
for (int i = 0; i < no_of_courses; i++) {
a[i] = sc.next(); // accepting string inputs
}
System.out.println("Enter the course to be searched:");
String search = sc.next(); // entering a string to search
boolean flag = false;
for (int i = 0; i < no_of_courses; i++) {
if (a[i].equals(search)) // I feel the problem is here
{
flag = true;//do not print here. just decide whether course is available or not
break;
}
}
//at the end of for loop check your flag and print accordingly.
if(flag) {
System.out.println(search + "course is available");
}else {
System.out.println(search + "course is not available");
}
}
}
}

class Course {
public static void main(String[] args)
{
Scanner sc = new Scanner(System.in);
String a[] = new String[20] ; //assuming max 20 strings
System.out.println("Enter no. of courses");
int no_of_courses = sc.nextInt(); // number of strings
if(no_of_courses <= 0)
System.out.println("Invalid Range");
else
{
System.out.println("Enter course names:");
for(int i=0 ; i < no_of_courses ; i++)
{
a[i] = sc.next(); //accepting string inputs
}
System.out.println("Enter the course to be searched:");
String search = sc.next() ; //entering a string to search
boolean found = false;
for(int i = 0 ; i < no_of_courses ; i++)
{
if(a[i].equalsIgnoreCase(search)) //I feel the problem is here
{
**found = true;**
break;
}
}
if(found) {
System.out.println(search+ "course is available");
}else {
System.out.println(search+ "course is not available");
}
}
}
}

This is really a good effort and you almost got it. So just a couple of things
Since you are inputting the number of courses, just use that value to initialise your array (it's just a good practice to get into to try not initialise things before you actually need them).
If you are doing String comparisons and case sensitivity does not matter, rather use .equalsIgnoreCase(String)
To solve your problem, you just needed a boolean variable to indicate whether or not you had found a match. Initially this would be FALSE (no match found) and you would run through your array until a match is found. Once found this would be flagged TRUE and you'd breakout your loop (which you correctly did).
Only once out your loop, you'd print out whether you found a match.
Have a look:
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.println("Enter no. of courses");
int no_of_courses = sc.nextInt(); // number of strings
if (no_of_courses <= 0) {
System.out.println("Invalid Range");
} else {
String a[] = new String[no_of_courses];
System.out.println("Enter course names:");
for (int i = 0; i < a.length; i++) {
a[i] = sc.next(); //accepting string inputs
}
System.out.println("Enter the course to be searched:");
String search = sc.next(); //entering a string to search
boolean courseFound = Boolean.FALSE;
for(int i = 0; i < a.length; i++) {
if (a[i].equalsIgnoreCase(search)) {
courseFound = Boolean.TRUE;
break;
}
}
if(courseFound) {
System.out.println(search + "course is available");
} else {
System.out.println(search + " course is not available");
}
}
}
Oh, just for interest (and when you start working with some more advanced constructs), you could always just use stream, which was introduced in Java 8. It'll trim down 12 lines to 5...
if(Arrays.stream(a).anyMatch(i -> i.equalsIgnoreCase(search))) {
System.out.println(search + " course is available");
} else {
System.out.println(search + " course is not available");
}

I noticed a few things - Does your program run to the end? When i copy/pasted into my ide i noticed a few missing semi-colons, and like Yhlas said, your last if/else statement syntax is incorrect.
And this doesn't have anything to do with whether or not your program will give you the right answer, but your last loop will print over and over again because it will check each element in a, and each time it loops and finds a mismatch it will print something out

For loop: populate array from user input [duplicate]

This question already has answers here:
Scanner is skipping nextLine() after using next() or nextFoo()?
(24 answers)
Closed 4 years ago.
I was setting up a small app that asks a user to determine the array size and then populate it. The used "for" loop skips the index 0; but I'm uncertain why.
If you run this code with 1 as the array size it skips over the user inputting the first word.
The issue is certainly on the for-loop but it is so simple that I don't see it.
Thanks!
import java.util.Scanner;
public class WordRandomizerAdvanced {
public static void main(String[] args) {
int arrayDimesion;
Scanner sc = new Scanner(System.in);
System.out.println("****************************************************");
System.out.println("******** Welcome to Word Randomizer ADVANCED********");
System.out.println("****************************************************");
//Get array size
System.out.println("How many words would you like to enter?");
arrayDimesion = sc.nextInt();
String[] wordArray = new String[arrayDimesion];
//Populate with user input
for (int i=0; i<arrayDimesion; i++) {
System.out.println("Please enter a word");
wordArray[i] = sc.nextLine();
}
//Print all entered Strings
System.out.println("This are the words you entered: ");
for(int i = 0; i < wordArray.length; i++) {
System.out.println(wordArray[i]);
}
//Print random string from array
int r = (int)(Math.random() * wordArray.length);
System.out.println("The random word is: " + wordArray[r]);
}
}

Change your
arrayDimesion = sc.nextInt();
to
arrayDimesion = Integer.parseInt(sc.nextLine());
Reason: sc.nextInt() doesn't consume the newline character that you give after taking arrayDimesion input. This later on gets consumed in the next sc.nextLine() call.
PS: It might throw NumberFormatException. So you can handle it like :
try {
arrayDimesion = Integer.parseInt(sc.nextLine());
} catch (NumberFormatException e) {
e.printStackTrace();
}

The below code is clean, easy to read and handles the edge cases.
import java.util.Scanner;
public class WordRandomizerAdvanced {
public static void main(String[] args) {
int numOfWords;
Scanner scanner = new Scanner(System.in);
System.out.println("****************************************************");
System.out.println("******** Welcome to Word Randomizer ADVANCED********");
System.out.println("****************************************************");
//Get array size
System.out.println("How many words would you like to enter?");
numOfWords = Integer.parseInt(scanner.nextLine());
String[] wordArray = new String[numOfWords];
//Populate with user input
System.out.println("Please enter the word(s)");
for (int i = 0; i < numOfWords; i++) {
wordArray[i] = scanner.nextLine();
}
//Print all entered Strings
System.out.println("These are the words you entered: ");
for (int i = 0; i < numOfWords; i++) {
System.out.println(wordArray[i]);
}
//Print random string from array
if (numOfWords == 0) {
System.out.println("You didn't enter a word");
} else {
int r = (int) (Math.random() * numOfWords);
System.out.println("The random word is: " + wordArray[r]);
}
}
}

Hangman code stuck on three different problems

I'm trying to make a hangman game. On each turn, the user guesses a letter. If they guessed correctly, they can guess again. Otherwise, their remaining available guesses drops by one, and the guessed letter is put into an array.
When the user hits zero remaining guesses, the program is supposed to ask if they want to play again. If they answer yes, it is supposed to restart the game, and if they answer no, the program ends.
The problem I'm having is with the array that holds the guesses, and with restarting the game.
Also, the program will error every once in a while when starting. The error is
Exception in thread "main" java.lang.NullPointerException at Hangman1.main(Hangman1.java:27)
The error when trying to restart the game is
Exception in thread "main" java.lang.NullPointerException at Hangman1.main(Hangman1.java:101)
searchArray is the method that is supposed to take the position of the char array and copy that in asterisk array and return asterisk array, that doesn't seem to work. Running debug it seems the problem that causes the program to crash is that word will sometimes end up null, but only sometimes and I don't really know why
import java.util.*;
import java.io.*;
public class Hangman1 {
static Scanner keyboard = new Scanner(System.in);
public static final int MAXSIZE = 15000;
public static final int NUM_GUESS = 8;
public static final int WORD_LENGTH = 20;
public static void main(String[] args) {
int random = pickrandom(MAXSIZE);
try {
// Set up connection to the input file
Scanner input = new Scanner(new FileReader("dictionary.txt"));
instructions();
keyboard.nextLine();
clearScreen();
String word = randomWord(input, random);
System.out.println(word);
String[] charArray = word.split("");
System.out.print("\n");
String[] asterisk = asteriskLine(word);
String decision = "Y";
//decision = keyboard.nextLine().toUpperCase();
System.out.println("Word to guess :");
for (int count = 0; count < word.length(); count++) {
System.out.print(asterisk[count]);
}
System.out.print("\n");
int tries = NUM_GUESS;
System.out.println("Enter a letter to guess or 9 to quit");
String guess = keyboard.next();
String[] wrongGuesses = new String [NUM_GUESS];
int guessMade = 0;
do {
//System.out.println(tries);
while (!(guess.equals("9")) && !(guess.equals(word)) && (tries > 0))
{
String letter = guess.substring(0,1);
if (word.indexOf(letter) < 0) {
clearScreen();
tries--;
wrongGuesses = wrongGuesses(guessMade, wrongGuesses, letter);
printArray(asterisk, charArray, word, tries, wrongGuesses, guessMade);
guessMade++;
guess = keyboard.next();
}
else {
clearScreen();
asterisk = searchArray(charArray, asterisk, guessMade, letter, word);
printArray(asterisk, charArray, word, tries, wrongGuesses, guessMade);
guess = keyboard.next();
}
if (charArray == asterisk) {
System.out.println("You won!");
}
if (tries == 0) {
System.out.println("You have no more guesses left");
}
}
if (guess.equals("9")) {
System.out.println("Thanks for playing");
}
System.out.println("Play again? Y/N");
decision = keyboard.next().toUpperCase();
if (decision.equals("Y")) {
random = pickrandom(MAXSIZE);
word = randomWord(input, random);
charArray = word.split("");
System.out.print("\n");
asterisk = asteriskLine(word);
guess = keyboard.next();
}
} while (decision.equals("Y"));
//System.out.println("Play again? Y/N");
//decision = keyboard.nextLine().toUpperCase();
}
catch (FileNotFoundException e) {
System.out.println("There was an error opening one of the files.");
}
}
//Clears screen after introduction
private static void clearScreen() {
for (int blanks = 0; blanks < 80; blanks++) {
System.out.println();
}
}
// This method returns a randomly selected integer
// between 0 and count-1
public static int pickrandom(int count) {
Random generator = new Random();
return generator.nextInt(count);
}
// Places asterisks in place of the letters in the word
// Parameter is the string word. it holds mystery word
public static String[] asteriskLine(String word) {
int i;
String[] asteriskArray = new String [word.length()];
for (i = 0; i < word.length(); i++) {
asteriskArray[i] = "* ";
}
return asteriskArray;
}
public static void instructions() {
System.out.println(" H A N G M A N. "
+ "\n This is a word guessing game. "
+ "\n A word will be selected at random and kept hidden. You will try to figure out the secret word by"
+ "\n guessing letters which you think are in the word. "
+ "\n You will guess one letter at a time. "
+ "\n If the letter you guess is correct, the position(s) of the letter in the secret word will be shown. "
+ "\n You will be allowed "
+ NUM_GUESS
+ " wrong guesses If you guess incorrectly "
+ NUM_GUESS
+ " times, you lose the game. "
+ "\n If you guess all of the letters in the word, you win."
+ "\n\n Press enter to continue ");
}
public static String randomWord(Scanner input, int random) {
String[] dictionaryWords = new String [MAXSIZE];
int usedsize = 0;
while (usedsize < MAXSIZE && input.hasNextLine()) {
dictionaryWords[usedsize] = input.nextLine();
usedsize++;
}
String word = dictionaryWords[random];
return word;
}
//Replaces correct guess in blanks
public static String correctWord(String guess, String word, String asterisk, char letter) {
return null;
}
public static void printArray(String[] asterisk, String[] charArray, String word, int tries, String[] wrongGuesses, int guessMade) {
System.out.println("Word to guess");
for (int count = 0; count < word.length(); count++) {
System.out.print(asterisk[count]);
}
System.out.println("\nGuesses remaining: " + tries);
System.out.print("Incorrect letters tried: ");
for (int count = 0; count <= guessMade; count++) {
System.out.print(wrongGuesses[count] + " ");
}
System.out.println("\nEnter a letter to guess or 9 to quit");
}
public static String[] wrongGuesses(int guessMade, String [] wrongGuesses, String letter) {
wrongGuesses[guessMade] = letter;
return wrongGuesses;
}
public static String[] searchArray(String[] charArray, String[] asterisk, int guessMade, String letter, String word) {
int[] a = new int[word.length()];
for (int count = 0; count < word.length(); count++) {
if (letter == charArray[count]) {
asterisk[count] = charArray[count];
}
}
return asterisk;
}
}

One thing that you need to do is to read all of your words in once and only once, and store them all into an ArrayList. Your current code tries to re-use a Scanner object that is already spent, and that will fail. Instead get your random word from the ArrayList<String>.

Running debug it seems the problem that causes the program to crash is
that word will sometimes end up null, but only sometimes and I don't
really know why
public static String randomWord(Scanner input, int random) {
String[] dictionaryWords = new String [MAXSIZE];
int usedsize = 0;
while (usedsize < MAXSIZE && input.hasNextLine()) {
dictionaryWords[usedsize] = input.nextLine();
usedsize++;
}
String word = dictionaryWords[random];
return word;
}
Sometimes random will be bigger than usedsize.
So you need to move this line from outside the loop
int random = pickrandom(MAXSIZE);
into this function, and have the maximum be usedsize (or usedsize-1).
You can protect yourself against this error, and work out whether you should be using usedsize or usedsize-1, by writing a unit test. Look into a Junit tutorial.
In your junit test, call randomword and pass it a very high value for random. Then
assert(word!= null)
Word is null when random is longer than the length of your dictionary.

Hangman Code Issue (Java)

I am trying to create a simple hangman program in java for a school assignment and I have it working for the most part. The main problem I have with it is that it keeps printing out the hidden word twice. It also only goes through and asks the user to enter an word 8 times when it should be 15 times. Can someone tell me where I went wrong?
// Its in a separate method.
public static void application1() throws Exception {
// Tells the user about the game.
System.out.println("Welcome to Hangman!");
System.out.println("Please try to guess the word within 15 letters.");
String option = "";
// Creates a array of all the phrases.
String answer[] = new String[20];
answer[0] = "computer";
answer[1] = "radio";
answer[2] = "calculator";
answer[3] = "teacher";
answer[4] = "bureau";
answer[5] = "police";
answer[6] = "geometry";
answer[7] = "president";
answer[8] = "subject";
answer[9] = "country";
answer[10] = "environment";
answer[11] = "classroom";
answer[12] = "animals";
answer[13] = "province";
answer[14] = "month";
answer[15] = "politics";
answer[16] = "puzzle";
answer[17] = "instrument";
answer[18] = "kitchen";
answer[19] = "language";
do {
// Creates a random number to choose which word to choose from.
int rand = (int)(Math.random() * 20 + 0);
StringBuffer word = new StringBuffer("");
// This makes the unknown word as long as the actual word.
for (int i = 0; i < answer[rand].length(); i++) {
word.append("_");
}
System.out.println(word);
char input = ' ';
// This is where it checks the input and replaces the letters.
for (int i = 0; i < 15; i++) {
input = (char) System.in.read();
for (int j = 0; j < answer[rand].length(); j++) {
if (input == answer[rand].charAt(j)) {
word.setCharAt(j, input);
}
}
// This is where the hidden word get printed twice.
System.out.println(word);
}
// Asks the user if they want to restart the application.
System.out.println("Would you like to try again? (Y/N)");
option = input();
} while (option.equalsIgnoreCase("y"));
}

Use a Scanner to get your input.
Scanner in = new Scanner(System.in);
String line = in.nextLine();
char input = line.charAt(0);
I think System.in.read(); is returning the entered character and the enter key. (the \n char).
That makes your cycle run twice for each input, printing two times and looking like it only accepts 8 chars.

if (word.equals(answer[rand])) {
System.out.println("Congratulations! You guessed the word!");
// Asks the user if they want to restart the application.
System.out.println("Would you like to try again? (Y/N)");
option = input();
}
else if (i == 14) {
System.out.println("Sorry, you did not guess the word.");
// Asks the user if they want to restart the application.
System.out.println("Would you like to try again? (Y/N)");
option = input();
// Returns to the main menu.
menu();
}
This doesn't recognize the word is correct.

Java - Scanner does not remove all of the desired objects

I am trying to make some kind of 'Evil Hangman game' (nifty Stanford CS exercises). The purpose of the game is to 'cheat' by removing as many possible word solutions as possible so the user cannot guess before the very end.
I have made a loop (below) which seems to remove many of the words possible words but for some reason it does not remove all of them. The input is a dictionary.txt file which contains about 120K words.
When I 'guess' the letter "a" it will take away roughly 60-70% of the words with "a" in them (estimate based on comparisons between the output with the first couple of words in the txt file)
File file = new File("dictionary.txt");
Scanner textScan = new Scanner(file);
List<String> wordList = new ArrayList<String>();
while ( textScan.hasNext() )
{
word = textScan.next();
wordList.add(word);
}
System.out.println("The ArrayList has " + wordList.size() + " objects stored in it.");
Scanner textScan1 = new Scanner(file);
for(int i = 0; i <= guessNumber; i++)
{
Collections.sort(wordList);
System.out.println("Type in your guess as a letter ");
String guess = keyboard.next();
guess = guess.toLowerCase();
while ( textScan1.hasNext() )
{
String word1 = textScan1.next();
if (wordLength != word1.length() && word1.contains(guess))
{
wordList.remove(word1);
}
}
}
I am aware that my code is a bit messy at this point, I am trying to improve everything about my programming so all feedback is greatly appreciated! I have the feeling that I am including stuff that does not have to be there and so on.
I will post the whole code below in case that helps:
import java.util.*;
import java.lang.*;
import java.io.*;
public class EvilHangman
{
public static void main(String[] args) throws IOException
{
// declaring variables
int wordLength;
int guessNumber;
// initiate the scanner
Scanner keyboard = new Scanner( System.in );
// introduction and prompting the user for word length
System.out.println("Welcome to Hangman. Let's play! ");
System.out.println("Please enter the desired word length: ");
wordLength = keyboard.nextInt();
while(wordLength < 0 || wordLength > 26)
{
System.out.println("This is not a valid word length. ");
System.out.println("Please enter the desired word length: ");
wordLength = keyboard.nextInt();
}
// prompt the user for number of guesses
System.out.println("How many guesses do you want to have? ");
guessNumber = keyboard.nextInt();
while(guessNumber < 0)
{
System.out.println("Number of guesses has to be a postive integer. ");
System.out.println("Please enter the desired number of guesses: ");
guessNumber = keyboard.nextInt();
}
// count the number of words with the specified length
/* int wordCount = 0;
String word = null;
while ( textScan.hasNext() )
{
word = textScan.next();
if (word.length() == wordLength)
{
wordCount++;
}
}
*/
// prompts the user whether he/she wants a running count of word length - using next() instead of nextLine() to clear buffer
/* System.out.println("Do you want a running total of number of words remaining? ");
String runningTotal = keyboard.next();
if (runningTotal.equalsIgnoreCase("yes"))
System.out.println("Words with that length: " + wordCount);
*/
// create a list (array) of all the words that matches the input length
String word = null;
File file = new File("dictionary.txt");
Scanner textScan = new Scanner(file);
List<String> wordList = new ArrayList<String>();
while ( textScan.hasNext() )
{
word = textScan.next();
wordList.add(word);
}
System.out.println("The ArrayList has " + wordList.size() + " objects stored in it.");
Scanner textScan1 = new Scanner(file);
for(int i = 0; i <= guessNumber; i++)
{
Collections.sort(wordList);
System.out.println("Type in your guess as a letter ");
String guess = keyboard.next();
guess = guess.toLowerCase();
while ( textScan1.hasNext() )
{
String word1 = textScan1.next();
if (wordLength != word1.length() && word1.contains(guess))
{
wordList.remove(word1);
}
}
}
System.out.println("The ArrayList has " + wordList.size() + " objects stored in it.");
System.out.println(wordList);

Finally figured out it had to do with the scanner. It had to be initiated inside the loop
for(int i = 1; i <= guessNumber; i++)
{
Scanner textScan2 = new Scanner(file1);
System.out.println("Type in your guess as a letter ");
String guess = keyboard.next();
//System.out.print(guess);
while ( textScan2.hasNext() )
{
String word1 = textScan2.next();
if (wordLength != word1.length() || (word1.contains(guess)))
{
wordList.remove(word1);
}
}
}