So i'm supposed to collect data from user inputs for a game
int[] player1 = new int[4];
try {
player1[4] = Integer.parseInt(keyin.nextLine());
}
catch(NumberFormatException e) {
System.out.println("Player 2 : "); }
The try-catch is to skip to the next player when player1 presses Enter, but the problem I'm getting is I can't seem to find a way to use the variables the player1 has inputted. I need those values to compare with another, but using int player1[0] does not work.
Where can I find the values the person has entered?
An example of the program running:
Player 1: 12 1 5 // these numbers are user inputted
Player 2: 12 4 3
[...]
You need to setup a loop to both read in the inputs, as well as to display those inputs.
Your code below does not work; you are trying to access data that is beyond the bounds of your array.
player1[4] = Integer.parseInt(keyin.nextLine());
If you declare you array like this: int[] player1 = new int[4];
Then you have the following indexes to use:
| 0 | 1 | 2 | 3 |` //This gives you 4 indexes! But player1[3] is the last usable index
Remember that when you are trying to access elements of arrays or any element in programming, computers begin numbering at zero! Any attempt to access data beyond this can result in undesired behavior, casuing the program to terminate abruptly.
I encourage you to examine the following resources:
http://docs.oracle.com/javase/tutorial/java/nutsandbolts/arrays.html
http://www.tutorialspoint.com/java/java_loop_control.htm
http://www.programmingsimplified.com/java/tutorial/java-while-loop
Scanner input = new Scanner(System.in);
System.out.println("Input an integer");
while ((n = input.nextInt()) != 0) {
System.out.println("You entered " + n);
System.out.println("Input an integer");
}
System.out.println("Out of loop");
}
String string = keyin.nextLine();
String[] parts = string.split("[ ]+");
Then check the size of parts and loop through that.
Related
I am new to JAVA and this is what I have to do:
Accept a set of marks (out of 100). The user should press the Enter button after each mark is entered and the mark should then be added to an ArrayList of Integers.
This is what I have so far:
int score = Integer.parseInt(marksinput.getText());
ArrayList<Integer> marks = new ArrayList();
Collections.addAll(marks, score);
String out = "";
String Out = null;
int[] studentmarks = {score};
for (int item : studentmarks) {
marksoutput.setText(""+item);
}
if (score > 100) {
marksoutput.setText("Enter marks\n out of 100");
}
This only adds one mark in the arraylist and I need user to input as many marks he wants. I know that my arraylist is wrong, which is why it only takes 1 number but I do not know how to make all the input numbers go in arraylist. What I have is that it takes the number and if user inputs another number, it just replaces the older number. I want it to display both the numbers not just one. Any help is appreciated and thank you in advance!☻☻
(This is not a duplicate even though others have the same title)
In case what you are after is a program that adds any integer typed by the user into an ArrayList, what you would have to do is the following:
Scanner scanner = new Scanner(System.in);
List<Integer> ints = new ArrayList<Integer>();
while(true)
ints.add(scanner.nextInt());
What this program will do, is let the user input any number and automatically puts it into an ArrayList for the user. These integers can then be accessed by using the get method from the ArrayList, like so:
ints.get(0);
Where the zero in the above code sample, indicates the index in the ArrayList from where you would like to retrieve an integer.
Since this website is not there to help people write entire programs, this is the very basics of the ArrayList I have given you.
The ArrayList is a subclass of List, which is why we can define the variable using List. The while loop in the above example will keep on going forever unless you add some logic to it. Should you want it to end after executing a certain amount of times, I would recommend using a for loop rather than a while loop.
Best regards,
Since it seems you are really new,
What you are looking for is a for-loop
From the Java documentation, he is the syntax of a for-loop in Java
for (initialization; termination; increment) {
statement(s)
}
Initialization: Obviously you want to start from 0
Termination: you want to stop after 100 inputs, so that's 99 (starting from zero)
Increment: you want to "count" one by one so count++
for(int counter = 0; counter < 100; counter++) {
//Ask user for input
//read and add to the ArrayList
}
So before you enter the for-loop you need to initialize the ArrayList, and a Scanner to read input:
Scanner sc = new Scanner(System.in);
ArrayList<Integer> list = new ArrayList();
for(int counter=0; counter < 100; counter++) {
System.out.println("please enter the " + counter + " number");
int x = sc.nextInt();
list.add(x);
}
I have an assignment to make a program which allows the user to enter an unlimited
set of numbers until 0 is entered, to print the smallest and largest number, and to say if they are odd or even.
I am comfortable with everything except on how to allow the user to enter as many numbers as desired and am unsure on how to start this. Should I be using loops or another method?
Please note I only began learning Java last week and so am unfamilliar with the language
Many thanks!
I am comfortable with everything except on how to allow the user to enter as many numbers as desired and am unsure on how to start this. Should I be using loops or another method?
Since this is a homework, and you probably do not want us to do your homework for you. This is what you can do:
do{
//prompt user for input
//prompt user to continue (y/n)
//if 'n' was given
//proceed = false;
}while(proceed);
You can use a do-while or while loop. You can now prompt user for input infinitely till they decide to stop.
Update 1: (According to changes in question)
Terminating condition: when 0 is received as input:
do{
//prompt user for integer input
//if (input == 0)
//break; (exit loop)
//store input
}while(input != 0);
***Try to do it on your own.Use this for reference only.
I know its not right to give away the code as it is for your assignment.Just use (understand and learn)this if you didn't get the output.
int n=0,temp=0,z=0,i=0,j=0;
int []a=new int[1000]; //as size is not given by user assign the array with a much greater value
BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); //Object for BufferedReader class used for reading elements
do{
System.out.print("Enter the number:");
a[n]=Integer.parseInt(br.readLine()); //String to integer conversion
n++;
System.out.println("Do you want to enter more numbers(0/1):");
z=Integer.parseInt(br.readLine());
}while(z!=0);
//Sorting
for(i=0;i<n;i++){
for(j=i+1;j<n;j++){
if(a[i]>a[j])
{
temp=a[i];
a[i]=a[j];
a[j]=temp;
}
}
}
//Now after sorting the smallest number will be in the first location ie;
//"0" so inorder to check it is even or odd we take check its remainder when it is divided by 2.
if(a[0]%2==0){
System.out.println("The smallest number is : "+ a[0] + " & the number is even");}
else{
System.out.println("The smallest number is : "+ a[0] + " & the number is odd");}
if(a[n-1]%2==0){
System.out.println("The largest number is : "+ a[n-1] + " & the number is even");}
else{
System.out.println("The largest number is : "+ a[n-1] + " & the number is odd");}
A sample output is as follows :
I have an issue for creating an array based on the total amount of numbers entered into the array.
Essentially the program is expected to work as the following: the user is prompted for n numbers to enter into an array. So until the user types '000' as their input, the user will be prompted for a new number.
Note: for this array, I do not want the user to input the amount of numbers they want to enter for the array size. Instead, I want the user to continue inputting random numbers until '000' has been inputted, then, the total amount of numbers that has been entered into the array, is the size of such array.
For example: this would work if we have int array[] = {1, 2, 4, 6}, this will automatically set array size to 4, without actually explicitly declaring the array size as 4 elements. Similarly, with my code, I want it where the numbers that the user enters is added to the array, and then the array size is automatically given from the amount of numbers the user has entered like above.
It is important to note that we do not know the length of the array until the user has entered all n numbers.
I have attempted a skeleton, but it returns a cannot find symbol error:
Code:
//Array Code
import java.util.*;
class setArray {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
int stopInput = 000;
int number;
System.out.print("Enter a number: ");
number = input.nextInt();
while(number != stopInput) {
System.out.print("Enter a number: ");
number = input.nextInt();
int array[] = {number};
}
System.out.print("Array size: " + array.length);
} // Main brace
} // Class brace
setArray.java:19: error: cannot find symbol
System.out.print("Array Size: " + array.length);
symbol: variable array
location: class setArray
1 error
You have a few errors here. The first is understanding why you get your immediate error. The variable array is declared within the scope of the while loop. It can not be seen outside of this loop. That is why the compiler is complaining.
The second is that the size of the array (if declared outside of the loop) will always be 1. From my understanding of what you have written as an attempt to solve the problem you have describe shows that you are not tackling the problem correctly.
While you don't known the the final length of the array to be entered; you do need to store the values entered (my inference) to populate the final array. To store the value entered by the user you need a list that will grow with the input.
List<Integer> values = new ArrayList<>();
while (number != stopInput) {
System.out.print("Enter a number: ");
values.add(Integer.valueOf(input.nextInt()));
}
Integer[] array = values.toArray(new Integer[values.size()]);
Firstly, the compilation error is because the array variable is not visible from the System.out.println line. This is because it's declared inside the while loop, so is only visible inside the while loop.
To make it visible to the whole method, declare it before the while loop.
Secondly, arrays cannot be resized. You declare an array to be a certain size, and you cannot add or remove elements.
My suggestion would be to use an ArrayList. Declare one before your loop, and add the new number inside the loop. After the loop, the size should be how many numbers were entered.
Finally, there's no difference between 000 and 0. Is 0 a valid input number?
You can use
List<Integer> array=new ArrayList<Integer>();
while(number != stopInput) {
System.out.print("Enter a number: ");
number = input.nextInt();
array.add(number);
}
This sounds like a job for java.util.ArrayList - this is the array that doesn't have a fixed size and is growing as you add values to it automatically under the covers.
The error is caused because you are creating the array only within the scope of the while loop. You need to create it outside the loop. Secondly, standard arrays are not dynamic, so you would need to either set the size and increase it as needed, or just simply use an ArrayList.
Psuedo:
ArrayList<Integer> list = new ArrayList<Integer>()
...
while(not stop number)
list.add(number)
...
print(list.size())
If you really want to use an Array, here is how you can do it
public static void main(String[] args){
STOP_ENTRY = "000";
scan = new Scanner(System.in);
entry = "";
while(true){
System.out.print("Enter #: ");
String tempS = scan.nextLine();
if(tempS.equals(STOP_ENTRY)) break;
else entry += tempS + ":";
}
String[] split = entry.split(":");
int[] intArray = new int[split.length];
System.out.println("Length of created intArray = " + intArray.length); //length of created array
for(int i = 0; i < intArray.length; i++){
intArray[i] = Integer.parseInt(split[i]);
System.out.println("intArray[" + i + "] => " + String.valueOf(intArray[i]));
}
}
I would recommend an ArrayList, as it dynamically changes is size when you add an element, but do whatever you'd like.
An important note, this does not handle any malicious entry that you might not want (characters, symbols), and will error if they are entered, something you can easily add if you need
I am trying to have a method that takes the a five-dice random roll (int [] dice) and allows the user to say which dice they want to throw again (1st, 2nd, 3rd, 4th , or 5th die) like in the game Yahtzee. I also have to validate that the user picked a number between 1 and 5, that they don't put a duplicate number, and that they don't enter more than 4 numbers to roll again. If the requirements aren't satisfied, I need to out print "Illegal die!" and ask the user to enter again. Whichever die/ dice they choose needs to be randomized again and be assigned to the dice[] array. This is what I have so far that basically takes the user string input and changes it to integers and I can't figure out how to do the other things I mentioned above. Any help would be greatly appreciated!
public static void throwAgain(int[] dice) {
Scanner keyboard = new Scanner(System.in);
System.out.print("List which die to throw again: ");
String line = keyboard.nextLine();
String [] strArray = line.split(" ");
int [] intArray = new int[strArray.length];
for (int i = 0; i < intArray.length; i++){
intArray[i] = Integer.parseInt(strArray[i]); // Changes user's string input to an array of integers
}
// Arrays.sort(intArray);
}
I also have to validate that the user picked a number between 1 and 5
Check each int as you are looping. > and < are useful.
that they don't put a duplicate number
Make a subloop that will check each previous value. = is useful.
and that they don't enter more than 4 numbers to roll again.
.length and > are useful.
If the requirements aren't satisfied, I need to out print "Illegal die!"
Have a boolean flag error that starts out as false and set it to true when a validation check fails. At the end, check the flag. System.out.println is useful.
and ask the user to enter again.
while is useful. Set error as true at the top, and false as the loop starts. Loop while there is an error.
Whichever die/ dice they choose needs to be randomized again and be assigned to the dice[] array
Loop over the intArray, and assign new random values to the dice elements whose indices are one less than each element of intArray. [], - and java.util.Random are useful.
I want to make a program which keeps prompting the user to input integers(from CUI) until it receives a 'X' or 'x' from the user.
The program then prints out the maximum number, minimum number and average value of the input numbers.
I did manage to get the user to input numbers until someone types 'X', but I can't seem to get it to stop if someone types 'x' and the second bit.
This is the code that I have managed to work out:
Scanner in = new Scanner(System.in);
System.out.println("Enter a number")
while(!in.hasNext("X") && !in.hasNext("x"))
s = in.next().charAt(0);
System.out.println("This is the end of the numbers");
Any hints on how I proceed further?
You will need to do something like this:
Scanner in = new Scanner(System.in);
System.out.println("Enter a number")
while(!(in.hasNext("X") || in.hasNext("x")))
s = in.next().charAt(0);
System.out.println("This is the end of the numbers");
Whenever you use while loop you have to use the {} in case the arguments in the while block are more than 1 line, but if they are just of a line then you can just go on without using the {}.
But the problem, you had I suppose is the use of && instead of ||. What the && (AND) operator does is execute if both the statements are true but a || (OR) Operator works if any of the conditions are true.
If you say while(!in.hasNext("X") && !in.hasNext("x")) it makes no sense as the user input is not both at the same time, but instead if you usewhile(!in.hasNext("X") || !in.hasNext("x"))` it makes sense. Understood?
And about sorry, im really new at this. but ive added the code No problem, you need not say sorry but there are a few things to keep in mind before asking a question. You must read this https://stackoverflow.com/help/how-to-ask and yeah one more thing, you should use proper English Grammar while framing your question.
Last of all, about how to calculate the average..., for that what you need to do is store all the input variables into an array and then take out the mean of that or alternatively you could think about it and code something up yourself. Like to take out mean, you could make a variable sum and then keep adding the integers the user enters and also keep a variable count which will keep the count of the number of integers entered and then at last you could divide both of them to have your answer
Update: For checking the minimum and the maximum, what you can do is make 2 new variables like int min=0, max=0; and when the user enters a new variable you can check
//Note you have to change the "userinput" to the actual user input
if(min>userinput){
min=userinput;
}
and
if(max<userinput){
max=userinput;
}
Note: At stackoverflow we are there to help you out with the problems you are facing BUT you cannot exploit this. You cannot just post your homework here. But if you are trying to code something up and are stuck at it and cannot find a answer at google/stackoverflow then you can ask a new question and in that you need to tell what all you have already tried. Welcome to SO! :D Hope you have a nice time here
This would fit your needs:
public void readNumbers() {
// The list of numbers that we read
List<Integer> numbers = new ArrayList<>();
// The scanner for the systems standard input stream
Scanner scanner = new Scanner(System.in);
// As long as there a tokens...
while (scanner.hasNext()) {
if (scanner.hasNextInt()) { // ...check if the next token is an integer
// Get the token converted to an integer and store it in the list
numbers.add(scanner.nextInt());
} else if (scanner.hasNext("X") || scanner.hasNext("x")) { // ...check if 'X' or 'x' has been entered
break; // Leave the loop
}
}
// Close the scanner to avoid resource leaks
scanner.close();
// If the list has no elements we can return
if (numbers.isEmpty()) {
System.out.println("No numbers were entered.");
return;
}
// The following is only executed if the list is not empty/
// Sort the list ascending
Collections.sort(numbers);
// Calculate the average
double average = 0;
for (int num : numbers) {
average += num;
}
average /= numbers.size();
// Print the first number
System.out.println("Minimum number: " + numbers.get(0));
// Print the last number
System.out.println("Maximum number: " + numbers.get(numbers.size() - 1));
// Print the average
System.out.println("Average: " + average);
}