Trying to design a simple lottery program. Everything works except checking if the numbers entered are between 1 to 59.
Exercise says the numbers must be stored in a String variable.
so
if(num<0 || num>59) //wont work for me
Tried making another variable
int numConverted = Integer.parseInt(num)
We haven't covered converting String to int in class though so I don't think this is what expected. Got confused trying that way anyway so probably this is wrong.
Here is the code I have currently.
{
Scanner scan = new Scanner(System.in);
String num=""; //num variable is empty untill user inputs numbers
for(int i =0; i<6; i++)
{
System.out.println("Enter your number between 1-59");
num = num +" "+ scan.nextLine();
}
System.out.println("Ticket printed £2. Your numbers are " + num);
}
In your posted code it's obvious that you want the User to supply 6 specific numerical values. These values are appended to the String variable named num (space delimited). You need to obviously do a few things here:
1) Make sure the value supplied by the user is indeed a numerical value;
2) Make sure the numerical values supplied fall within the minimum and maximum scope of the lottery itself (which you have stated is: 1 to 59);
3) Make sure the number entered by the User hasn't been supplied already.
You've been tasked to store the entered values into a String data type variable and that is all fine but at some point you want to carry out value comparisons to make sure that all the entered values actually play within the limits of the lottery.
When the User completes his/her entries, you end up with a space delimited string held in the num string variable. You now need to make sure that these values entered are indeed....numbers from 1 to 59 and none contain alpha characters.
In my opinion (and this is only because you need to store entered values into a String variable), it's best to use your String variable to gather User input, then test the input to make sure it is indeed a string representation of an actual integer number. Once this is established then we test to make sure if falls within the value min/max limits (1-59). Now we need to test to make sure the number entered hasn't already been entered before for this ticket.
Of course with each test described above, if one fails then the User should be prompted to re-enter a proper value. You can do this by utilizing a while loop. Plenty examples of this in StackOverflow but here's a quick example:
Scanner scan = new Scanner(System.in);
String ticketNumbers = "";
for(int i = 0; i < 6; i++) {
Boolean isOK = false;
while (!isOK) {
System.out.println("\nPlease enter your desired 6 ticket numbers:\n"
+ "(from 1 to 59 only)");
String num = scan.nextLine();
//Is the string entered an actual integer number?
//We use the String.matches() method for this with
//a regular expression.
if(!num.matches("\\d+")) {
System.out.println("You must supply a numerical value! "
+ "Try Again...");
continue;
}
if (ticketNumbers.contains(num + " ")) {
System.out.println("The number you supplied has already been chosen!"
+ " Try Again...");
continue;
}
if (Integer.parseInt(num) >= 1 && Integer.parseInt(num) <= 59) {
ticketNumbers+= num + " ";
isOK = true;
}
else {
System.out.println("The number you supply must be from "
+ "1 to 59! Try Again...");
}
}
}
System.out.println("Ticket printed £2. Your numbers are " + ticketNumbers);
How about -
if(Integer.parseInt(num) < 0 || Integer.parseInt(num) > 59)
This should work, place it after the input.
If it works, please mark this as correct, I need the rep!!!
Easy way would be add available numbers (suppose it wont grow more than 60. You can use a loop to add to this as well)
String numbers[] = {"1","2","3", "..."};
Then inside the loop
Arrays.asList(numbers).contains(num);
You can remove prefixing zero in order avoid conflicts with values like '02'
Here everything is String related.
If you don't want to explicitly convert to int, you could use a regular expression.
if (num.matches("[1-5]?[0-9]")) {
...
This checks whether the String consists of (1) maybe a digit from 1 to 5, followed by (2) definitely a digit from 0 to 9. That'll match any number in the range 0-59.
If you've got a whole series of numbers separated by spaces, you could expand this to cover a whole series like this.
if (num.matches("([1-5]?[0-9]\\s+)*[1-5]?[0-9]")) {
This matches any number of repetitions (including zero) of "a number followed by spaces", followed by a single repetition without a space. The "\\s" means "any whitespace character", the "+" after it means "one or more of what precedes", and the "*" means "zero more of what precedes" - which in this case is the term in parentheses.
Oh I see what you are trying to do
This is what you want
Scanner scan = new Scanner(System.in);
String allNums = "";
for(int i =0; i<6; i++)
{
System.out.println("Enter your number between 1-59");
int num = scan.nextInt();//Take the number in as an int
if(num >0 && num < 59)//Check if it is in range
{
allNums += num + " ";//if it is add it to a string
}
else
{
System.out.println("Number not in range");
i--;//go back one iteration if its not in range
}
}
System.out.println("Ticket printed £2. Your numbers are " + allNums);
Related
I am stuck in this program that is string method, my issue is that I cannot get the loop to stop and the program to print the output that is currently stored after the keyword has been entered. I am not trying to compare strings, I am trying to input multiple strings and add a word, in this case, "not" to the strings until the word "stop" is entered. Once "stop" has been entered. the system will output the entire string stored.
Here is the question for the program:
(StringConcat.java) This program asks the user to repeatedly enter a String. It ,should concatenate those Strings together, but insert spaces and the word “not” between every pair of words the user enters. Stop when the user enters the String “stop”. Display the final String. For instance, the program output might look like:
Please enter some Strings:
"Such"
"eyes"
"you"
"have"
"stop"
"Such not eyes not you not have"
Here is my code so far:
import java.util.*;
public class StringConcat{
public static void main(String [] args){
Scanner sc = new Scanner(System.in);
String s = new String();
System.out.print("Please enter some Strings: ");
for(int x=0; x<s.length(); x++){
s = sc.nextLine();
s = s + "not ";
if(s == "stop"){
System.out.println(s);
break;
}
else{
continue;
}
}
}
}
Several issues with your code:
(1) Why do you use a for loop and iterate up to s.length() when the length of s (which is 0 at that point) has nothing to do with your problem?
You need a loop which has not predefined number of iterations like a while (true) from which you will exit with a break.
(2) In each iteration you get the user's input and store it in s, so you lose all previous values.
You need a separate variable to store the user's input.
(3) The continue statement is not needed as the last statement in a loop.
(4) Because at each iteration you append " not " at the end, after the loop has finished you must delete that last " not " from s
(5) Don't use == when you compare strings. There is the method equals() for this.
This is my solution:
Scanner sc = new Scanner(System.in);
String s = "";
System.out.print("Please enter some Strings: ");
while (true){
String input = sc.nextLine();
if(input.equalsIgnoreCase("stop"))
break;
s += input + " not ";
}
if (s.length() >= 5)
s = s.substring(0, s.length() - 5);
System.out.println(s);
Use while loop.
Why while loop?
Usually we have to use while loops always when we don't know the number of loops we will do. In this case only when the user inputs "stop".
So you need a String field to hold the user words. Also we can use a number field to track if is the first or the second word, thinkg in append the "not" word.
Then, take a look in this example:
Scanner s = new Scanner(System.in);
String currentAnswer = "";
String userWords = "";
int tracker = 0;
while (!currentAnswer.equals("stop")){
currentAnswer = s.nextLine();
userWords += currentAnswer + " ";
if (tracker % 2 != 0) {
userWords += "not ";
}
tracker++;
}
System.put.println(userWords);
This can be done using for loop too but I really recommend the while loop to this case.
EDIT:
As you saw, I used equals() instead == to compare two Strings because we are wiling to check for its value, not for its object equality.
When we use == operator we are trying to check if two objects target to the same memory adress, but we only want to know if two Strings have the same value.
For this case is valid to know that we can compare it using other ways, such as Objects.equals() or even contentEquals().
Check this discussion to learn more about comparing strings.
This question already has answers here:
Why Wont My Java Scanner Take In input?
(3 answers)
Closed 7 years ago.
When I run my code, it works right up until it asks the question "which operation do you want to use from ( sum , subst , multi , div )". No matter what the user picks, there is no response from my program!
Why is this happening?
import java.util.Scanner;
import java.io.*;
public class three3 {
public static void main (String[] args) {
int x;
int y;
int opera;
String oper;
Scanner in = new Scanner (System.in);
System.out.println(" write the first number ");
x = in.nextInt();
System.out.println(" write the second number ");
y = in.nextInt();
System.out.println(" which operation do you want to use from ( sum , subst , multi , div )");
oper = in.nextLine();
if (oper == "sum") {
opera=x+y;
System.out.println(" the sum of two numbers is " + opera );
}
if (oper == "subst") {
opera = x - y;
System.out.println(" the subtraction of two numbers is " + opera );
}
if (oper == "multi") {
opera = x * y;
System.out.println(" the multi of two numbers is " + opera );
}
if (oper == "div") {
opera = x / y;
System.out.println(" the division of two numbers is " + opera );
}
}
}
Because none of those if-clauses is executed.
You're comparing Strings with == which is wrong. Use oper.equals("sum") instead. See this question for reference. The conclusion for you is to always use equals for Strings.
You need to call in.nextLine() right after the last call to in.nextInt() The reason is that just asking for the next integer doesn't consume the entire line from the input, and so you need skip ahead to the next new-line character in the input by calling in.nextLine().
int y = in.nextInt();
in.nextLine();
This pretty much has to be done each time you need to get a new line after calling a method that doesn't consume the entire line, such as when you call nextBoolean() etc.
In addition, you don't check for String equality with the == operator, use the .equals() String method instead.
The problem is that in.nextLine() consumes the \n inserted implicitly when you clicked enter after the int was entered. That means that the program doesn't expect any other input from the user. To fix this you could consume a new line with in.nextLine() before putting it int your actual variable, something like this:
System.out.println(" write the second number ");
y=in.nextInt();
System.out.println(" which operation do you want to use from ( sum , subst , multi , div )");
in.nextLine(); //New line consuming the \n
oper=in.nextLine();
if(oper.equals("sum")){//replace == by .equals
opera=x+y;
}
Apart from that, and as runDOSrun said, you should replace the comparisons of strings from a==b to a.equals(b)
Adding on to other people's points, you should also consider using else if{} and else{} statements so you can catch invalid input.
I'm very new to programming, especially Java. I need to create a program that counts how many orders each entry at a restaurant gets ordered. The restaurant carries 3 entries, hamburgers, salad, and special.
I need to set up my program so that the user inputs, say, "hamburger 3", it would keep track of the number and add it up at the end. If the user inputs "quit", the program would quit.
System.out.println("Enter the type (special, salad, or hamburger) of entrée followed by the number, or quit to exit the program.");
I'm thinking about using a while loop, setting it so if the user input != to "quit", then it would run.
What's difficult for me is I don't know how to make my program take into account the two different parts of the user input, "hamburger 3" and sum up the number part at the end.
At the end, I want it to say something like "You sold X hamburgers, Y salads, and Z specials today."
Help would be appreciated.
You'll probably want three int variables to use as a running tally of the number of orders been made:
public class Restaurant {
private int specials = 0;
private int salads = 0;
private int hamburger = 0;
You could then use a do-while loop to request information from the user...
String input = null;
do {
//...
} while ("quite".equalsIgnoreCase(input));
Now, you need some way to ask the user for input. You can use a java.util.Scanner easily enough for this. See the Scanning tutorial
Scanner scanner = new Scanner(System.in);
//...
do {
System.out.println("Enter the type (special, salad, or hamburger) of entrée followed by the number, or quit to exit the program.");
input = scanner.nextLine();
Now you have the input from the user, you need to make some decisions. You need to know if they entered valid input (an entree and an amount) as well as if they entered an available option...
// Break the input apart at the spaces...
String[] parts = input.split(" ");
// We only care if there are two parts...
if (parts.length == 2) {
// Process the parts...
} else if (parts.length == 0 || !"quite".equalsIgnoreCase(parts[0])) {
System.out.println("Your selection is invalid");
}
Okay, so we can now determine if the user input meets or first requirement or not ([text][space][text]), now we need to determine if the values are actually valid...
First, lets check the quantity...
if (parts.length == 2) {
// We user another Scanner, as this can determine if the String
// is an `int` value (or at least starts with one)
Scanner test = new Scanner(parts[1]);
if (test.hasInt()) {
int quantity = test.nextInt();
// continue processing...
} else {
System.out.println(parts[1] + " is not a valid quantity");
}
Now we want to check if the actually entered a valid entree...
if (test.hasInt()) {
int quantity = test.nextInt();
// We could use a case statement here, but for simplicity...
if ("special".equalsIgnoreCase(parts[0])) {
specials += quantity;
} else if ("salad".equalsIgnoreCase(parts[0])) {
salads += quantity;
} else if ("hamburger".equalsIgnoreCase(parts[0])) {
hamburger += quantity;
} else {
System.out.println(parts[0] + " is not a valid entree");
}
Take a look at The if-then and if-then-else Statements and The while and do-while Statements for more details.
You may also find Learning the Java Language of some help. Also, keep a copy of the JavaDocs at hand, it will make it eaiser to find references to the classes within the API
These two methods should be what you're looking for.
For splitting: String.split(String regex)
http://docs.oracle.com/javase/7/docs/api/java/lang/String.html#split(java.lang.String)
For parsing String into an Interger: Integer.parseInt(String s)
http://docs.oracle.com/javase/7/docs/api/java/lang/Integer.html#parseInt(java.lang.String)
You can split your strings using input.split(" "). This method gives you two strings - two parts of the main string. The character you splitted with (" ") won't be found in the string anymore.
To then get an integer out of your string, you can use the static method Integer.parseInt(inputPartWithCount).
I hope this helps!
I'm running a java program I created that stores data inputted by user. Specifically 4 array lists which are songName, songArtist, songYear & songAlbum.
I have a user input for "songYear" and I only want the program to accept a maximum of 4 digits in length and give an error otherwise, how can this be achieved?
here's the code I have for my add entry method:
public void addEntry(){
String newName = ui.getString("Enter the name of the track");
songName.add(newName);
String newArtist = ui.getString("Who performs this track");
songArtist.add(newArtist);
String newAlbum = ui.getString("What album is this track from");
songAlbum.add(newAlbum);
System.out.print("What year was the track released? ");
int newYear=input.nextInt(4);
songYear.add(newYear);
System.out.println("\n" + "Thank you, " +songName.get(songName.size()-1) + " has been added to the library.");
System.out.println("\n" + "Press 2 to view your library." + "\n");
}
You can use regex like: ^.{4}$
Means only if user typed 4 digits - return true, otherwise return false
To be sure that user used 4 numbers YYYY use something like:
^(?=[1-9]+)\d{4}$
Makes sure the year is 1 or 2 followed by three numbers; valid ranges in this case would be 1000-2999
^(?=[1-2][0-9]+)\d{4}$
Finally your code should be like:
if(inputUserStr.matches("^(?=[1-2][0-9]+)\d{4}$")){
// do some stuff
}
else{
// print error about valid input form [YYYY]
}
Depends entirely on the language but some approaches are:
check the string input using a len function; or
convert it to an integer and ensure it's less than 10,000; or
a regular expression like ^\d{1,4}.
No doubt there'll be other validation checks such as ensuring string input is all-numeric, and you're not trying to input a song that was written twenty years in the future, but they're added checks you should consider.
1) Accept the user's input and using the substring method, save only the first four characters (Specify to user that first 4 characters are considered).
2) You can ask the user to reenter the value if it is not 4 characters:
Scanner sc = new Scanner(System.in);
String a = sc.next();
if (a.matches("...."))
{
System.out.print(a);
}
else
{
System.out.print("Input again:" );
a = sc.next();
}
I've written a sample regex for 4 characters. But you can always change it.
I want to create a program to output the number of occurrences of a letter in a word. Basicaly the output has to look like this:
Please enter a word—howdy
The word howdy has five characters.
What letter would you like to guess? (enter zero to quit) a
There are 0 A’s.
What letter would you like to guess? (enter zero to quit) b
There are 0 B’s.
This is what I got so far:
import java.util.Scanner;
public class LetterOccurence
{
public static void main(String[]args)
{
Scanner input=new Scanner(System.in);
String word;
String letter;
int letterNumber;
boolean [] alphabet = new boolean [27];
System.out.println("Please enter a word- ");
word=input.next();
System.out.println("The word "+ word + " has " + word.length() + " letters\n");
String lower = word.toLowerCase();
for(letterNumber=0;letterNumber<lower.length();letterNumber++)
{
alphabet[lower.charAt(letterNumber) - 'a'] = true;
}
//do
//{
System.out.println("What letter would you like to guess? (enter 0 to quit) ");
letter = input.next();
if (alphabet[letter.charAt(0)-'a'] = true)
{
System.out.printf("There are %s's\n",letter.charAt(0));
}
else
{
System.out.printf("There are 0 %s's\n",letter.charAt(0));
}
//}while(Character.isLetter(letter.charAt(0)));
}
}
I am now stuck, any ideas on how to continue?
For a start, booleans only hold a true or false value, you can't count with them. Rather than in your loop setting each element in the array that maps to a certain character to true, you could simply increment the counter.
In this case you're going to require an int as opposed to a boolean. And to print out the amount of occurrences for a specific letter, you obviously just print out the int value at that specific index of the array.
An alternative is also a Map<Character,Integer>, rather than calculating the index for specific chars in your array.
EDIT: As Dave mentioned, your if statement is also broken.
If nothing else, that if statement in your commented-out do/while is using a single = (assignment) instead of == (comparison).
All you really need to do is keep a single count per guess, initialize it to zero, and each time you encounter the guessed letter, increment it.
If you're trying to do all that work "up front" before guessing, then you don't really need a map of booleans, you need a map of ints, one per lower-case letter, initialized to zero, and incremented each time its corresponding letter is guessed.
You're very close.
You don't want a boolean array for alphabet -- that only tells you what letters appear in the word, but not how many of each. Try this instead:
boolean [] alphabet = new boolean [27];
for(letterNumber=0;letterNumber<lower.length();letterNumber++)
{
++alphabet[lower.charAt(letterNumber) - 'a'];
}
Then later:
System.out.printf("There are %d %s's\n",alphabet[letter.charAt(0) - 'a'], letter.charAt(0));