Develop Reference

Java - word scrambler [keeping first and last letter]

My assignment is to write a program to scramble a word while maintaining the same first and last letter and only swapping two letters, then prompt the user to continue if they wish.
Example: userInput = bacon | Output = bcaon
I've attached an imagine of my program, there may be several issues, but as it stands I can't really run it due to the errors in the image. I'm really confused because I got a TA to help me on this assignment, and they seemed to think this would definitely work, but as you can see it does not.
I would really appreciate if someone could tell me what exactly is wrong and why. And if you have anything to add to make this program work, I'd really, really appreciate that too, but bottom line is I just want to understand what's wrong and why.
import java.util.Scanner;
import java.util.Random;
public class FreeStyle {
public static void main(String[] args) {
Scanner in = new Scanner(System.in); // Importing and initializing keyboard to 'in'
System.out.println("Please enter a word to be scrambled"); // Asking user for a word
String word = in.next(); // Initializing the user's input
System.out.println(swapLetters(word));
System.out.println("Would you like to enter another word? y/n");
String answer = in.next();
boolean userDone = true; //Using a Boolean statement to ask the user if they are done enter words or not
while (userDone) {
if (answer.equals('y')) {
System.out.println("Please enter a new word"); //Ask user for new word to scramble
word = in.nextLine(); //New initialization for 'word'
} else if (answer.equals('n')) { //If user types 'n', loops then breaks because while(userDone) is false
userDone = false;
} else {
System.out.println("Invalid input, please enter more than 3 letter words."); // The logic doesn't flow or apply to words that are less than 4 letters, so this catches that error and notifies the user
}
}
}
private static String swapLetters(String word) { //Private method used for the program only, no need to involve the user
Random r = new Random(); //Using random instead of math floor
//int arraysize = word.length();
int a = r.nextInt(word.length()-2)+1;
int b = r.nextInt(word.length()-2)+1;
//String word2 = word.substring(a, a+1);
String word2 = word.substring(0, a) + word.charAt(b)+word.substring(a+1, b)+word.charAt(a)+word.substring(b+1);
return word2;
}

Several points:
Why not use something already done exactly for what you are trying to do - Collections.shuffle? See comments in the code for understanding how it works.
You can't use equals() between a String and a char (' ' are for chars, " " are for Strings). Simple fix - just put your 'y' into "y", same for 'n'.
I've refactored the code at the beginning that we used to get user input and then scramble into a separate method, so we can reuse it again - getInputAndScramble.
And finally, I've used a do-while loop to keep looping until the user stops the loop with the "n" letter.
Please see my comments in the code, hopefully will clear things up.
public class Scrambler {
public static void main(String[] args) {
boolean userDone = true;
String word;
Scanner in = new Scanner(System.in);
getInputAndScramble(in); //Extracted method to get Scanner input and scramble
do {
System.out.println("Would you like to enter another word? y/n");
word = in.next();
while (userDone) {
if (word.equals("y")) {
getInputAndScramble(in);
break;
} else if (word.equals("n")) {
userDone = false;
} else {
System.out.println("Invalid input, please enter more than 3 letter words.");
}
}
} while (userDone); //continue until "n"
}
private static void getInputAndScramble(Scanner in) {
System.out.println("Please enter a word to be scrambled");
String word = in.next();
System.out.println(swapLetters(word));
}
private static String swapLetters(String word) {
/* Convert word into an ArrayList of characters.
Create ArrayList size of word,
convert String word into a char array and insert every char in
the char array into our ArrayList.
*/
ArrayList<Character> chars = new ArrayList<>(word.length());
for (char c : word.toCharArray()) {
chars.add(c);
}
//Shuffle, omitting first and last letters
Collections.shuffle(chars.subList(1, chars.size()-1));
//Add shuffled letters into an array to output as a word entity
char[] shuffled = new char[chars.size()];
for (int i = 0; i < shuffled.length; i++) {
shuffled[i] = chars.get(i);
}
//Return shuffled String
return new String(shuffled);
}
}

You are assuming that the two random number a and b have the property that a < b. What if a >= b? Then word.substring(a+1, b) will throw an error.
To fix it, just make sure that a < b is maintained (regenerating, swapping, etc.).
But to be sure, there are more than just this bug in your code. For example, using next(), comparing String with char, using wrong newline character, not striping newline character, and so on. You might want to add some print statements in your code you see what is actually happening.

Well, as for the swapping function, something like that should work:
private static String swapLetters(String word) {
char[] temp = word.toCharArray();
char swapHelper;
Random r = new Random();
int a = r.nextInt(word.length()-2)+1;
int b = r.nextInt(word.length()-2)+1;
swapHelper = temp[a];
temp[a] = temp[b];
temp[b] = swapHelper;
word = String.copyValueOf(temp);
return word;
}
Basically, im converting string to char array so i can operate on them with ease. A and B are variables that contain index of letters that should be swapped. After that, array is converted back to string and returned.

charAt(0) Not returning first number but second

Piglatin translator. at the end I am trying to get the location of the first vowel. Index is set to be the location of every vowel, but with pig latin you only need the location of the first vowel. When I run the program I don't always get the location of the first vowel. it seems to give me the second number and not the first.
import java.util.Scanner;
import javax.swing.JOptionPane;
public class Assignment_4_Piglatin {
public static void main(String[] args) {
Scanner userWord = new Scanner(System.in);
System.out.println("K. Caleb Swallow");
System.out.println("Welcome to the Pig Latin Translator!");
boolean run = true;
while (run) {
System.out.println("Please enter a word(or press Q to quit):");
String firstLetter = "something";
String firstVowel = "test";
String word = userWord.next();
String vowels = "aeiou";
if (word.equals("Q")) {
System.exit(0);
}
firstLetter = Character.toString(word.charAt(0));
if (firstLetter.equals("a") || firstLetter.equals("e") || firstLetter.equals("i") || firstLetter.equals("o") || firstLetter.equals("u")) {
System.out.println(word + "way");
} else {
for (int index = 0; index < word.length(); index++) {
if (vowels.contains(String.valueOf(word.charAt(index)))) {
System.out.print(index);
String firstNumber = Integer.toString(index);
firstVowel = Character.toString(firstNumber.charAt(0));
}
}
}
System.out.println(firstVowel);

The example seems to have some redundant code in if..else condition. If you want to print the first vowels then you can do it with a simple for loop, e.g.:
String word = userWord.next().toLowerCase();
String vowels = "aeiou";
for(int i=0 ; i<word.length() ; i++){
if(vowels.contains(String.valueOf(word.charAt(i)))){
System.out.println(word.charAt(i));
break;
}
}
Please note that you need to do toLowerCase on the actual word in order for contains to work.

There are a few problems I can see off the bat, but the one that is likely causing this error is in these lines:
String firstNumber = Integer.toString(index);
firstVowel = Character.toString(firstNumber.charAt(0));
Think about what this is doing. First, you are making a String out of the index value, then you are saying that the first vowel is at the 0th index of that string.
Think of this example: hello
The program will run and assign "4" to firstNumber and firstVowel which isn't what you want.
However, if you only have one vowel, your program will "work".
What happens if you have over ten vowels? I know this isn't a realistic example, but say it happens. Your program will assign the index of the last vowel to firstNumber (say it's 15), then it will assign the first character of that to firstVowel (1). This doesn't make much sense at all, does it, especially if you don't have a vowel in index 1.
The main problem you are encountering for words less than 10 letters in length is that you are not just outputting the second number, you are outputting the last one. One way I like to deal with this is to go through the code and put in print statements where I'm not sure what a certain value is. For example, I'd put another print statement in your loop which tells you what letter you're looking at, like so:
System.out.println("LETTER: "+ String.valueOf(word.charAt(index)));
This will help you avoid confusion. The proper way to do this problem would be to use a break statement, such as in Darshan's answer. Alternatively, you could use the properties of the for loop:
firstVowel = "";
for (int index = 0; index < word.length() && firstVowel == ""; index++) {
CODE
}
Note that the second part of the for loop is a conditional statement. You already know that this can be used to cycle through the word's characters, but you can insert any logical statement there that you want. For this example, I set the default value of firstVowel to "" (setting it to null is a faux-pas, but that's another story). Then, each time the loop runs, it checks to see if the value of firstVowel has been changed, which will of course happen on the first time a vowel is run through the loop.
So in short, you need to modify the two lines at the beginning of my post and you need to find a way to break your loop when you find the first vowel. One solution has been given here, and another in Darshan Mehta's post.

public static void main(String[] args) {
Scanner userWord = new Scanner(System.in);
System.out.println("K. Caleb Swallow");
System.out.println("Welcome to the Pig Latin Translator!");
boolean run = true;
while (run) {
System.out.println("Please enter a word(or press Q to quit):");
String firstLetter = "something";
String firstVowel = "test";
String word = userWord.next();
ArrayList<Character> vowels = new ArrayList<>();
vowels.add('a');
vowels.add('e');
vowels.add('i');
vowels.add('o');
vowels.add('u');
if (word.equals("Q")) {
System.exit(0);
}
firstLetter = Character.toString(word.charAt(0));
if (firstLetter.equals("a") || firstLetter.equals("e") || firstLetter.equals("i") || firstLetter.equals("o") || firstLetter.equals("u")) {
System.out.println(word + "way");
} else {
for (int index = 0; index < word.length(); index++) {
char indchar = word.charAt(index);
if (vowels.contains(word.charAt(index))) {
System.out.println(index);
firstVowel = Character.toString(word.charAt(index));
System.out.println(firstVowel);
index = word.length();
}
}
}
}
}
This is how I would do it. I changed the vowels String to an ArrayList so you can easily check if the char in the String word with the index is a vowel and the code works absolutely fine. It returns you the index where the first vowel is and what vowel it is.

Finding the number of occurances of a letter within a word in java

So first of all, hello everyone this is my first time stackoverflow as a question asker and I know you folks don't like people asking homework questions on here but I've been struggling with this for about a week now and have given it several reasonable attempts so I actually need help here and am not just trying to mooch answers off you amazing coders :)
So my task at hand is I'm trying (the language is java btw) to find the number of times a letter (which the user inputs) occurs in a word (which the user also picks, and then to output the number of time that word occurs, for example: the word hello has two 'l's in it.. it should be pretty easy but for some reason I can't get it :/
I believe using my current code the variable "let" gets turned into an ascii character and idk what to do with that, or rather how I should compare it with all the other characters in the word.
Please help :)
import java.util.Scanner;
public class LetterCounter {
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
String word = "";
String letter;
int limit = 0;
String input = null;
String let;
int count = 0;
int j = 0;
while(limit == 0){
System.out.println("Type a word.");
word = scan.nextLine();
System.out.println("Type a single letter.");
letter = scan.nextLine();
let = letter.substring(0,1);
char car;
while(j<word.length()){
car = word.charAt(j);
for(int x=1; x==j; x++){
if(let.charAt(0)==car){
count ++;
}
}
j+=1;
}
System.out.println(count + " " + "occurances.");
}
}
}

Here is a sample code that should work
import java.util.Scanner;
public class LetterCounter {
/**
* #param args the command line arguments
*/
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
System.out.println("Type a word.");
String word = scan.nextLine();
System.out.println("Type a single letter.");
String letter = scan.nextLine();
char let = letter.charAt(0);
int count = 0;
for (char char1: word.toCharArray()) {
if (char1 == let) {
count++;
}
}
System.out.println(count + " " + "occurrences.");
}
}
Here is the test output
Type a word.
letter
Type a single letter.
t
2 occurrences.

Char array updating

I have been working on my hangman program for far to long and cannot figure out why it is not replacing the characters entered with the asterisks.
There are a lot of details I have not added so please do not sit here and judge that. I need someone to tell my why the character the user enters is not replacing the asterisks and If you know what I could do to fix it please tell me.
I'm struggling. I have edited my program to show you where I know the logic error is coming from however I do not know what the error is.
String hiddenWord = wordList[rand];
char[] asterisks = new char[MAXCHAR];
hideWord(hiddenWord);
System.out.println(Arrays.toString(hideWord(hiddenWord)));
numGuess( hiddenWord,asterisks);
public static char[] hideWord(String hiddenWord)
{
int wordLength = hiddenWord.length();
//int length = wordLength * 2;
char[] asterisks = new char[wordLength];
for(int i=0; i < wordLength; i++)
{
asterisks[i] = '*';
}
return asterisks;
}
public static void numGuess(String hiddenWord,char[] asterisks)
{
Scanner keyboard = new Scanner(System.in);
hideWord(hiddenWord);
int remAttempts = MAXGUESS;
int i = 0;
while(i < (hiddenWord.length()-1))
{
System.out.println("Enter a letter or 9 to quit");
char guess = keyboard.next().charAt(i);
if(asterisks[i] == (hiddenWord.charAt(i)))
{
//attemtps == hiddenWord.charAt(i);
System.out.println("Nice job!");
remAttempts--;
}
i++;
}
}

Look at this code (I changed the formatting a bit):
while (i < hiddenWord.length() - 1) {
System.out.println("Enter a letter or 9 to quit");
char guess = keyboard.next().charAt(i);
//...
i++;
}
You're asking for a letter, but you really request a String with at least the size + 1 that equals i: keyboard.next().charAt(i);. Therefore, if you write just a letter, then you'll get an Exception at the second iteration of that loop.
I guess what you meant was: keyboard.next().charAt(0);. This will return the first character of the given String.
If this doesn't solve the problem, then provide the whole Stacktrace and mark the line in your code, where the Exception occurs.

Writing a program to count spaces in a phrase

I'm trying to write a program where a user would enter a phrase, and the program would count the blank spaces and tell the user how many are there. Using a for loop but i'm stuck, could someone help me out?
import java.util.Scanner;
public class Count
{
public static void main (String[] args)
{
String phrase; // a string of characters
int countBlank; // the number of blanks (spaces) in the phrase
int length; // the length of the phrase
char ch; // an individual character in the string
Scanner scan = new Scanner(System.in);
// Print a program header
System.out.println ();
System.out.println ("Character Counter");
System.out.println ();
// Read in a string and find its length
System.out.print ("Enter a sentence or phrase: ");
phrase = scan.nextLine();
length = phrase.length();
// Initialize counts
countBlank = 0;
// a for loop to go through the string character by character
for(ch=phrase.charAt()
// and count the blank spaces
// Print the results
System.out.println ();
System.out.println ("Number of blank spaces: " + countBlank);
System.out.println ();
}
}

The for loop for counting spaces would be written as follows:
for(int i=0; i<phrase.length(); i++) {
if(Character.isWhitespace(phrase.charAt(i))) {
countBlank++;
}
}
It reads as follows: “i is an index, ranging from the index of the first character to the index of the last one. For each character (gotten with phrase.charAt(i)), if it is whitespace (we use the Character.isWhitespace utility function here), then increment the countBlank variable.”

Just wondering, couldn't you just split the string entered by blank spaces and take the length of the array subtracted by 1?
In C# it would be as trivial as
string x = "Hello Bob Man";
int spaces = x.Split(' ').Length - 1;
Pretty sure java has a split? Works even if you have two contiguous spaces.

You have probably problem with that for each loop
char[] chars = phrase.toCharArray(); Change string into array of chars.
for(char c : phrase.toCharArray()) { //For each char in array
if(Character.isWhitespace(c) { //Check is white space.
countBlank++; //Increment counter by one.
}
}
or
for(int i =0; i <phrase.lenght(); i++) {
if(Character.isWhitespace(phrase.charAt(i)) { //Check is the character on position i in phrase is a white space.
countBlank++; //Increment counter by one.
}
}

You have to complete for cycle and count spaces
//replace this lines
for(ch=phrase.charAt()
// and count the blank spaces
//to this lines
for (int i = 0; i < phrase.length(); i++)
{
if(phrase.charAt(i) == ' ') countBlank++;
}

Loop through the characters in the string.
Check if the character is a space (char value = 32 or ch == ' ')
If space, add to countBlank, otherwise continue
Display the results.
You might look at the String and Character classes in the Java documentation for assistance.

I'm not very familiar with java, but if you can access each character in the string.
You could write something like this.
int nChars = phrase.length();
for (int i = 0; i < nChars; i++) {
if (phrase.charAt(i) == ' ') {
countBlank++;
}
}

This is at the following Java Tutorials
import java.util.regex.Pattern;
import java.util.regex.Matcher;
public class SplitDemo2 {
private static final String REGEX = "\\d";
private static final String INPUT = "one9two4three7four1five";
public static void main(String[] args) {
Pattern p = Pattern.compile(REGEX);
String[] items = p.split(INPUT);
for(String s : items) {
System.out.println(s);
}
}
}
OUTPUT:
one
two
three
four
five
The regex for whitespace is \s
Hope that helps.