Develop Reference

Java -how can I store an array in switch case

I need to build code that first gets a 2d array and then prints it.
for this, I built a menu with a switch case.
when the user clicks 0, the user types the size of the array (the size is always n*n), and then the user types the values. then I need to create a function that uses this info to build a char array.(the values is hex base 0-F)
when the user clicks 1, the code needs to print the same 2d array.
I have a difficult time understanding how I can move the array from case 0.
import java.util.Scanner;
public class Assignment3 {
static Scanner reader = new Scanner (System.in);
public static void main(String[] args) {
int checker=1;
int user_selction;
do {
user_selction=Menu();
switch(user_selction) {
case 0:
Menu_0(user_selction);
break;
case 1:
break;
case 2:
break;
case 3:
break;
case 4:
checker=GoodBye(checker);
break;
default:
break;
}
}while(checker==1);
}
public static int Menu ()
{
int menu_num;
System.out.println("~ Photo Analyzed ~");
System.out.println("0. Load Photo");
System.out.println("1. Print Photo");
System.out.println("2. Circle Check");
System.out.println("3. Random Check");
System.out.println("4. Exit");
System.out.println("Please select an option>");
menu_num=reader.nextInt();
if(menu_num>4||menu_num<0)
{
System.out.println("Invalid input");
}
return menu_num;
}
public static int GoodBye(int GB)
{
GB=0;
System.out.println("Goodbye!");
return GB;
}
public static int Menu_0 (int a)
{
int Ps;
System.out.println("Please insert the photo size>");
Ps=reader.nextInt();
if(Ps<0||Ps>12)
{
System.out.println("Invalid Photo Input!");
return a;
}
System.out.println("Please insert the photo value>");
String strPhoto;
do {
strPhoto = reader.nextLine();
} while(strPhoto.length() == 0);
if(strPhoto.length()!=Ps*Ps)
{
System.out.println("Invalid Photo Input!");
return a;
}
for(int i=0;i<Ps*Ps;i++)
{
if(strPhoto.charAt(i)<'0'||strPhoto.charAt(i)>'F')
{
System.out.println("Invalid Photo Input!");
return a;
}
}
return a;
}

This is an example
import java.util.Scanner;
public class Assignment3 {
static Scanner reader = new Scanner (System.in);
public static void main(String[] args) {
int checker=1;
int user_selction;
char [][]array = null;
do {
user_selction=Menu();
switch(user_selction) {
case 0:
array = Menu_0();
break;
case 1:
print_array(array);
break;
case 2:
break;
case 3:
break;
case 4:
checker=GoodBye(checker);
break;
default:
break;
}
}while(checker==1);
}
public static int Menu ()
{
int menu_num;
System.out.println("~ Photo Analyzed ~");
System.out.println("0. Load Photo");
System.out.println("1. Print Photo");
System.out.println("2. Circle Check");
System.out.println("3. Random Check");
System.out.println("4. Exit");
System.out.println("Please select an option>");
menu_num=reader.nextInt();
if(menu_num>4||menu_num<0)
{
System.out.println("Invalid input");
}
return menu_num;
}
public static int GoodBye(int GB)
{
GB=0;
System.out.println("Goodbye!");
return GB;
}
public static char[][] Menu_0 ()
{
int Ps;
System.out.println("Please insert the photo size>");
Ps=reader.nextInt();
if(Ps<0||Ps>12)
{
System.out.println("Invalid Photo Input!");
return null;
}
System.out.println("Please insert the photo value>");
char [][]array = new char[Ps][Ps];
for(int i=0;i<Ps;i++)
{
for (int j = 0 ; j < Ps ; j++)
{
char c = reader.next().charAt(0);
if(c<'0'||c>'F')
{
System.out.println("Invalid Photo Input!");
return null;
} else {
array[i][j] = c;
}
}
}
return array;
}
public static void print_array(char [][]array){
for (int i = 0 ; i < array[0].length ; i++)
{
for (int j = 0 ; j < array[0].length ; j++)
{
System.out.print(array[i][j] + " ");
}
System.out.println();
}
}
}

Use Scanner like this:
Scanner sc = new Scanner(System.in);
System.out.println("Select 1 to input array size or 2 to do sth");
int option = sc.nextInt();
switch(option) {
case 1 :
Scanner sc = new Scanner(System.in);
System.out.println("Enter array size: ");
int size = sc.nextInt()
int[] array = new array[size*size];
break;
case 2 :
something;
break;
default:
System.out.println("No such option ");
break;
}

Creating a Basic Java phone book

I'm just learning Java and trying to make a simple phone book. For this part I'm trying to prompt the user to choose one of the 3 options below.
public class PhoneBook {
public static void main (String[] args){
options();
/*This method prompts the user to enter phone number
String s;
Scanner in = new Scanner(System.in);
System.out.println("Enter Phone Number");
s = in.nextLine();
System.out.println("You entered phone number ");
System.out.println(s);*/
}
public static void options (){
//This method gives the user choices on what to do
char choice;
char enterNumber = 'n';
char showNumber = 's';
char closeBook = 'c';
String read;
String freeLine = "error";
Scanner keyboard = new Scanner(System.in);
while (true){
System.out.println("Please select from the following");
System.out.println("n to Enter the number");
System.out.println("s to Show the number ");
System.out.println("c to Close the Phone book");
read = keyboard.nextLine();
choice = read.charAt(0);
switch (choice) {
case 'n': enterNumber;
system.out.println();
case 's':showNumber;
system.out.println();
case 'c': closeBook;
break;
default: System.out.println("Invalid Entry");
}
}
}
}
When I compile it i get errors on lines 37, 39, and 41 saying "Error: not a statement". I feel like something is missing. If anyone can help it would be greatly appreciated.

I am assuming that with the following lines you want to achieve to print the letter n for enterNumber in the console?
case 'n': enterNumber;
system.out.println();
This is not correct Java syntax. You will have to pass the variable value to the System.out.println method call:
case 'n': System.out.println(enterNumber);
Also note that Java is case sensitive, so you have to spell System with a capital letter.
On a side note, you will want to break; after each of your case statements, otherwise the code of the following cases will be executed as well:
switch (choice) {
case 'n': System.out.println(enterNumber);
break;
case 's': System.out.println(showNumber);
break;
case 'c': System.out.println(closeBook);
break;
default: System.out.println("Invalid Entry");
}

you do not have to write variable after 'cast' statement.
Refer below code.
import java.util.Scanner;
public class PhoneBook {
public static void main (String[] args){
options();
/*This method prompts the user to enter phone number
String s;
Scanner in = new Scanner(System.in);
System.out.println("Enter Phone Number");
s = in.nextLine();
System.out.println("You entered phone number ");
System.out.println(s);*/
}
public static void options (){
//This method gives the user choices on what to do
char choice;
char enterNumber = 'n';
char showNumber = 's';
char closeBook = 'c';
String read;
String freeLine = "error";
Scanner keyboard = new Scanner(System.in);
while (true){
System.out.println("Please select from the following");
System.out.println("n to Enter the number");
System.out.println("s to Show the number ");
System.out.println("c to Close the Phone book");
read = keyboard.nextLine();
choice = read.charAt(0);
switch (choice) {
case 'n':
System.out.println();
case 's':
System.out.println();
case 'c':
break;
default: System.out.println("Invalid Entry");
}
}
}
}

I have made a special answer for you. I don't add additional explanation. It's a large answer. I tell more than you ask, but I've done my best to make a readable code, so that you can analyse step-by-step to understand what you need at least when trying to make a Phone Book (console test drive application). If you need more explanation, write under comments.
First make a PhoneEntry class:
import java.util.Objects;
public class PhoneEntry implements Comparable<PhoneEntry> {
// https://jex.im/regulex/#!embed=false&flags=&re=%5E%5Ba-zA-Z%5D%7B2%2C%7D((-%7C%5Cs)%5Ba-zA-Z%5D%7B2%2C%7D)*%24
private static final String NAME_PATTERN = "^[a-zA-Z]{2,}((\\-|\\s)[a-zA-Z]{2,})*$";
// https://jex.im/regulex/#!embed=false&flags=&re=%5E%5C%2B%3F%5Cd%2B((%5Cs%7C%5C-)%3F%5Cd%2B)%2B%24
private static final String NUMBER_PATTERN = "^\\+?\\d+((\\s|\\-)?\\d+)+$"; //^\+?\d+((\s|\-)?\d+)+$
private final String name;
private final String number;
public PhoneEntry(String name, String number) {
if (!name.matches(NAME_PATTERN) || !number.matches(NUMBER_PATTERN)) {
throw new IllegalArgumentException();
}
this.name = name;
this.number = number;
}
public String getName() {
return name;
}
public String getNumber() {
return number;
}
public boolean nameContainsIgnoreCase(String keyword) {
return (keyword != null)
? name.toLowerCase().contains(keyword.toLowerCase())
: true;
}
#Override
public boolean equals(Object obj) {
if (obj == null) {
return false;
}
if (!(obj instanceof PhoneEntry)) {
return false;
}
PhoneEntry phoneEntry = (PhoneEntry) obj;
return name.equalsIgnoreCase(phoneEntry.name)
&& number.equalsIgnoreCase(phoneEntry.number);
}
#Override
public int hashCode() {
int hash = 5;
hash = 17 * hash + Objects.hashCode(this.name.toLowerCase());
hash = 17 * hash + Objects.hashCode(this.number.toLowerCase());
return hash;
}
#Override
public int compareTo(PhoneEntry phoneEntry) {
return name.compareToIgnoreCase(phoneEntry.name);
}
}
Then the test drive
public class TestDrive {
private static final String choices = "nspc";
enum Choice {
CREATE, READ, PRINT, CLOSE;
static Choice getChoice(char c) {
switch (c) {
case 'n':
return Choice.CREATE;
case 's':
return Choice.READ;
case 'p':
return Choice.PRINT;
case 'c':
return Choice.CLOSE;
}
return null;
}
}
// Main
public static void main(String[] args) {
Scanner kbd = new Scanner(System.in);
final Set<PhoneEntry> entries = new TreeSet<>();
Choice choice;
while ((choice = getChoice(kbd)) != Choice.CLOSE) {
switch (choice) {
case CREATE:
PhoneEntry entry = getPhoneEntry(kbd);
if (entry != null) {
entries.add(entry);
}
break;
case READ:
print(readEntries(entries, kbd));
break;
case PRINT:
print(entries);
break;
}
}
}
private static Choice getChoice(Scanner kbd) {
System.out.println("\nPlease select from the following");
System.out.println("\tn to Enter the number");
System.out.println("\ts to Show numbers by keyword ");
System.out.println("\tp to Show all numbers ");
System.out.println("\tc to Close the Phone book");
System.out.print("> ");
String input = kbd.nextLine();
Choice choice = null;
if (!input.isEmpty()
&& choices.contains(input.toLowerCase())
&& ((choice = Choice.getChoice(input.toLowerCase().charAt(0))) != null)) {
return choice;
}
System.out.println("ERR: INVALID ENTRY. TRY AGAIN");
return getChoice(kbd);
}
private static PhoneEntry getPhoneEntry(Scanner kbd) {
System.out.print("Type contact name: ");
String name = kbd.nextLine();
System.out.print("Type phone number: ");
String number = kbd.nextLine();
try {
return new PhoneEntry(name, number);
} catch (IllegalArgumentException ex) {
System.out.println("\nERR: WRONG ENTRY");
}
return null;
}
private static void print(Set<PhoneEntry> entries) {
System.out.println("\nPHONE NUMBERS\n");
entries.stream().forEach(entry -> {
System.out.printf("Name: %s%nPhone: %s%n%n",
entry.getName(), entry.getNumber());
});
}
private static Set<PhoneEntry> readEntries(Set<PhoneEntry> entries, Scanner kbd) {
System.out.print("Type keyword: ");
return entries.stream().filter(entry
-> entry.nameContainsIgnoreCase(kbd.nextLine()))
.collect(Collectors.toCollection(TreeSet::new));
}
}

Instead of enterNumber;, you have to write enterNumber();.
The parentheses mean: Call the method.

How to validate the selection menu using a loop

Can someone edit my code to make it loop the selection menu. If the choice is not one of the 5 options it will prompt the user to re-enter until it is a valid option. If possible an explanation would be helpful as well. Thanks
Here is my code.
import java.util.*;
public class ShapeLoopValidation
{
public static void main (String [] args)
{
chooseShape();
}
public static void chooseShape()
{
while (true){
Scanner sc = new Scanner(System.in);
System.out.println("Select a shape number to calculate area of that shape!");
System.out.print("Circle = 1. \nRectangle = 2. \nTriangle = 3. \nExit = 4. \nINPUT : ");
int shapeChoice = sc.nextInt();
//while (true) {
if (shapeChoice >= 1 && shapeChoice <=4)
{
if (shapeChoice == 1)
{
circle();
}
else if (shapeChoice == 2)
{
rectangle();
}
else if (shapeChoice == 3)
{
triangle();
}
else if (shapeChoice == 4)
{
return;
}
}
else
{
System.out.print("Error : Choice " + shapeChoice + "Does not exist.");
}
}
class Test {
int a, b;
Test(int a, int b) {
this.a = a;
this.b = b;
}
}
}

First: take a look at switch
Second: read a bit about do-while loops (they are usually a good fit for this kind of situations).
Now, how I would implement it (but you should really learn how to make a loop in this scenarios):
public static void chooseShape () {
boolean valid = false;
do {
Scanner sc = new Scanner(System.in);
System.out.println("Select a shape number to calculate area of that shape!");
System.out.print("Circle = 1. \nRectangle = 2. \nTriangle = 3. \nExit = 4. \nINPUT : ");
int shapeChoice = sc.nextInt();
switch (shapeChoice) {
valid = true;
case 1:
circle();
break;
case 2:
rectangle();
break;
case 3:
triangle();
break;
case 4:
return;
default:
valid = false;
System.out.println("Error : Choice " + shapeChoice + "Does not exist.");
System.out.println("Please select one that exists.")
}
} while (!valid)
}

Use do-while flow control until EXIT code entered:
int shapeChoice;
do {
System.out.println("Select a shape number to calculate area of that shape!");
System.out.print("Circle = 1. \nRectangle = 2. \nTriangle = 3. \nExit = 4. \nINPUT : ");
int shapeChoice = sc.nextInt();
// then use if-else or switch
} while (shapeChoice != 4);
OR
use break statement to loop break at your code as bellow:
else if (shapeChoice == 4)
{
break;
}

Adding words and checking in Arraylist Hangman

I'm having trouble with adding words and using do while in my code:
ArrayList<String> word = new ArrayList<>();
word.add("fish");
word.add("chicken");
word.add("icecream");
int lengthz = word.size();
Scanner sc = new Scanner(System.in);
System.out.println("Hangman");
System.out.println("1. 1 Player");
System.out.println("2. 2 Player");
System.out.println("3. Add word");
System.out.println("4. Quit");
System.out.print("Choice : ");
int opsi = sc.nextInt();
if (opsi == 3) {
boolean show = false;
boolean founded = false;
System.out.println("Input the words to be added : ");
boolean showall = true;
do {
String input = sc.next() + sc.nextLine();
for (int i = 0; i < lengthz; i++) {
if (!input.equals(word.get(i))) {
while (!founded) {
word.add(input);
System.out.println("Succeed!");
founded = true;
}
} else if (input.equals(word.get(i))) {
while (!show) {
System.out.println("Already Added");
show = true;
}
}
}
System.out.println("Want to add more words?");
String answer = sc.next() + sc.nextLine();
if (answer.equals("no")) {
System.out.println("Thanks for adding");
showall = false;
} else if (answer.equals("yes")) {
opsi = 3;
}
} while (showall);
for (int i = 0; i <= lengthz; i++) {
System.out.println(word.get(i));
}
}
My desired output will be like if the user wants to add more word with "yes" then it will repeat the program, and if the user types "no" then it will display all the words together with the addition, and then going back to show the menu 1-4 option. Please help me ... Thanks in advance !

Structure your code, e.g. as follows:
static final Scanner in = new Scanner(System.in);
static List<String> words = getStandardWords();
public static void main(String[] args) {
while (true) {
System.out.println("-- Hangman --");
System.out.println("1. 1 Player");
System.out.println("2. 2 Player");
System.out.println("3. Add word");
System.out.println("4. Quit");
System.out.print("Choice : ");
String choice = in.nextLine();
switch (choice) {
case "1":
//todo
break;
case "2":
//todo
break;
case "3":
addWord();
break;
case "4":
System.exit(0);
break;
default:
System.out.println("Invalid choice: " + choice);
break;
}
}
}
static List<String> getStandardWords() {
List<String> result = new ArrayList<>();
result.add("fish");
result.add("chicken");
result.add("icecream");
return result;
}
static void addWord() {
System.out.println("Input the word to be added: ");
String word = in.nextLine();
// add word
if (words.contains(word)) {
System.out.println("Already Added");
} else {
words.add(word);
System.out.println("Succeed!");
}
// add more words?
while (true) {
System.out.println("Want to add more words?");
String choice = in.nextLine();
switch (choice.toLowerCase(Locale.ROOT)) {
case "n":
case "no":
System.out.println("Thanks for adding");
// print all words
for (int i = 0; i < words.size(); i++) {
System.out.println(words.get(i));
}
return;
case "y":
case "yes":
addWord();
return;
default:
System.out.println("Invalid coice: " + choice);
break;
}
}
}

1) You need to initialize the
founded = false;
inside do - while loop
2) use last printing for loop as below :
for(int i=0; i<word.size();i++)
{
System.out.println(word.get(i));
}

Hangman, exits the game without getting the user response (loop)

I got a couple issues with my code. I know it is not the best looking design/coding but I don't claim to be a good programmer yet. I have to other classes does their work correctly. Dictionary class which contains a word list and HangmanAnimation class which draws the hangman onto console.
Now, I want my game to ask to player if he/she wants to play again after the game finished. Actually, it does asking if player wants to play again but exits the game before the player can type anything.
I would appreciate any other suggestions aswell. Thanks in advance! You guys really rock! :)
public class HangmanGame {
public static void main(String[] args) {
HangmanUI ui = new HangmanUI();
ui.initialize();
String input = "";
if(ui.newGame(input).equalsIgnoreCase("yes"))
main(null);
}
}
public class HangmanUI {
private final Dictionary d = new Dictionary();
private final HangmanAnimation ha = new HangmanAnimation();
private String wordInProgress = d.getWordInProgress();
Scanner sc = new Scanner(System.in);
private int maxTries = 5;
String word;
public void initialize() {
int easyWords = 1;
int hardWords = 2;
System.out.println("Welcome to Hangman game.");
System.out.println("=========================");
System.out.println("Rules: You need to find the given word in 5 tries.");
System.out.println("You will continue guessing letters until you can either");
System.out.println("solve the word or all five body parts are on the gallows.");
System.out.println("In that case you will lose the game. Try not to enter");
System.out.println("same letter more than once. Those are counts too.");
System.out.println();
System.out.println("Choose your game level or Quit:");
System.out.println("1) Easy");
System.out.println("2) Hard");
System.out.println("3) Quit");
try {
int playersChoice = sc.nextInt();
switch (playersChoice) {
case 1:
d.wordList(easyWords);
break;
case 2:
d.wordList(hardWords);
break;
case 3:
System.out.println("Thank you for your time!");
System.exit(0);
default:
System.out.println("Invalid input. Try again!");
initialize();
}
word = d.pickRandomWord(d.getWordList());
hideWord(word);
while(maxTries > 0) {
if(wordInProgress.contains("-")) {
System.out.println(wordInProgress);
revealLetter(notifyGuess());
} else {
System.out.println("Good work! You found the word.");
}
}
} catch (InputMismatchException e) {
System.out.println("Invalid input. Use only digits!");
}
}
//TODO: Do not count same letter more than once & let player to know.
public char notifyGuess() {
ArrayList<Character> charSet = new ArrayList<>();
System.out.print("Please enter a letter: ");
char c = sc.next().charAt(0);
if(Character.isDigit(c)){
System.out.println("You can't use numbers. Please enter a letter.");
notifyGuess();
} else if(charSet.contains(c)) {
System.out.println("You already used '" + c + "' before.");
notifyGuess();
} else
charSet.add(c);
return c;
}
public void hideWord(String word) {
StringBuilder sb = new StringBuilder();
for(int i = 0; i < word.length(); i++) {
sb.append("-");
}
wordInProgress = sb.toString();
}
public void revealLetter(char c) {
try {
String temp = wordInProgress;
char[] charArray = wordInProgress.toCharArray();
for (int i = 0; i < word.length(); i++) {
if(c == word.charAt(i))
charArray[i] = word.charAt(i);
}
wordInProgress = new String(charArray);
if(temp.equals(wordInProgress)){
maxTries--;
ha.drawHanging(maxTries);
} else {
System.out.println("Good! There is '" + c + "' in the word.");
}
} catch (StringIndexOutOfBoundsException e) {
System.err.println("You have to enter a character!");
}
}
public String newGame(String input) {
System.out.println("Do you want to play again? (yes/no)");
input = sc.nextLine();
return input;
}
}

Try using this:
System.out.println("Do you want to play again? (yes/no)");
input = sc.next(); //<== here is the change
return input;