I have a HOMEWORK assignment that involves users inputs.
I want to ask the user for three integer inputs in the range 1-7 and store them in an array.
What I have so far seems to validate properly if all inputs are over 7 and rules out strings etc inputs and but still allows for a single input to be over 7.
Any help is appreciated.
Scanner in = new Scanner(System.in);
boolean valid = false;
int[] inputRange = new int[3];
while(!valid)
{
System.out.println("enter three numbers: ");
if(in.hasNextInt())
{
for(int i = 0; i< inputRange.length; i++)
{
inputRange[i] = in.nextInt();
if(inputRange[i] >= 1 && inputRange[i] <= 9){
valid = true;
}
}
}else{
in.next();
}
}
Your logic is fine, but you need to restart valid to false again each time user is going to enter a new digit.
Here's how you can validate user input to be between 1-9 with a do-while using your same logic just a little bit different.
Also next time be sure to post a valid MCVE and not just "snippets" (it should include a main method and imports)
import java.util.Scanner;
public class ValidationOfNumbers {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
boolean valid = false;
int[] inputRange = new int[3];
int counter = 0;
int number = 0;
System.out.println("Enter 3 digits between 1-9"); //Ask for digits, numbers can have multiple digits, while digits are numbers from 0-9
for (int i = 0; i < inputRange.length; i++) {
valid = false; //Restart "valid" variable for each new user input
do {
number = in.nextInt();
if (number >= 1 && number <= 9) {
valid = true; //If valid, it will exit do-while
} else {
System.out.println("Enter a valid digit between 1-9");
}
} while (!valid);
inputRange[i] = number; //We know it's valid because it went out of do-while, so we can now store it in the array
}
for (int i = 0; i < inputRange.length; i++) {
System.out.println(inputRange[i]);
}
}
}
Here is the code
Scanner in = new Scanner(System.in);
int count = 0;
int data[] = new int[3];
while(count < 3) {
if(in.hasNextInt()) {
int val = in.nextInt();
if(val>=1 && val <=7) {
data[count] = val;
count++;
}
}
else {
in.next();
}
}
Related
I am a beginner and have a simple piece of code that works - it is designed to ask a user for seven numbers and store them in an array then print out what they entered
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
int[] inputs = new int[7];
System.out.println("Enter 6 numbers and a bonus ball");
for (int i = 0; i < 7; i++) {
inputs[i] = in .nextInt();
}
System.out.println("You have entered the numbers:");
for (int i: inputs) {
System.out.println(i);
}
}
What I want to do is add an error trap to make sure the number is not greater than 49 - I have added the following code and there are no errors and it runs fine but I have to add two numbers for each loop as it only stores the second input - can anyone help tell me why?
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
int[] inputs = new int[7];
System.out.println("Enter 6 numbers and a bonus ball");
for (int i = 0; i < 7; i++) {
if ( in .nextInt() > 49) {
System.out.println("please enter a number less than 49");
inputs[i] = in .nextInt();
} else
inputs[i] = in .nextInt();
}
System.out.println("You have entered the numbers:");
for (int i: inputs) {
System.out.println(i);
}
}
when you do in.nextInt() it give you the "next" integer in the input, so you are doing this twice for each loop cycle, once in the if statement and the other in the if or else body. so you need invoke that function only once. something like this:
public static void main(String[] args)
{
Scanner in = new Scanner(System.in);
int [] inputs = new int [7];
System.out.println("Enter 6 numbers and a bonus ball");
for (int i = 0; i < 7; i++)
{
int current_input = in.nextInt()
if ( current_input > 49)
{
System.out.println("please enter a number less than 49");
inputs [i] = in.nextInt();
}
else
inputs [i] = current_input;
}
System.out.println("You have entered the numbers:");
for (int i : inputs)
{
System.out.println(i);
}
}
I don't test the code but you have the idea.
here you have another problem still, and is that when the user types a number over 49, the second time you ask the number to the user, you don't test again that it's below 49 so the user can enter any number.
Scanner scanner = new Scanner(System.in);
int grade[] = new int[3];
for (int i = 0; i < grade.length; i++) {
System.out.println("Enter your test score:");
grade[i] = scanner.nextInt();
}
I've been trying to figure out how to make it so if the user input is below 0 or above 100 it will ask again. I'm very new to Java and this is the first language I'm learning. I would appreciate any pointers. Do I need to use a do-while loop instead of a for loop for this? Or do I implement an if statement into the for loop?
You can validate the input by putting an if block inside the for loop.
However, since your loop will only execute three times, you should change your increment condition only when user enters correct input or else not.
You also can use while loop here.
Here is some example code:
for (int i = 0; i < grade.length; i++)
{
System.out.println("Enter your test score:");
if(grade[i] < 0 || grade > 100)
{
i--;
continue;
}
grade[i] = scanner.nextInt();
}
The if block will check that if the input is outside boundaries, decrement i and restart the loop.
What I suggest is, instead of incrementing i in loop, you can increase the value in if condition. Like below,
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
int grade[] = new int[3];
for (int i = 0; i < grade.length;) {
System.out.println("Enter your test score:");
int temp = scanner.nextInt();
if (temp >= 0 && temp <= 100) {
grade[i] = temp;
i++;
}else {
System.out.println("Please enter valid score");
}
}
scanner.close();
}
This basically gets a input value from user, if the value is greater or equal to 0 && lesser or equal to 100,then adds it to the Array and increments the loop count(array index value we can call it), else, prints message asking for valid input.
Instead of shoving the validation logic somewhere within the loop, you could also write a small utility method which neatly asks for valid input, and continues to do so until the user finally inputs something valid:
int promptInt(Scanner scanner, int min, int max, String errorMessage) {
while (true) {
int input = scanner.nextInt();
if (min <= input && input <= max) {
return input;
}
else {
System.out.println(errorMessage);
}
}
}
You could then simplify the loop:
int grade[] = new int[3];
for (int i = 0; i < grade.length; i++) {
System.out.println("Enter your test score:");
grade[i] = promptInt(0, 100, "Please enter a valid number");
}
I am a new-bee in java, I have a problem that i cant figure out to compare previous entered number(int) with next one continuously and I need to write a program that repeatedly reads numbers from the user’s keyboard. The program stops looping when the user types the same number twice in a row.
Thanks in advance for your kind guidance.
Here’s a sample run of the program:
5
13
21
5
4
5
5
Done!
Following was my unsuccessful effort :)
Scanner input = new Scanner(System.in);
System.out.println("Enter Numbers");
int x = 0;
int y = 0;
x = input.nextInt();
y = input.nextInt();
while (x != y) {
x = input.nextInt();
y = input.nextInt();
}
System.out.println("Done!!!!!!!");
input.close();
You can use loop to read number from console and stop if previous nubmer equals to current one. As marker of first number you can use e.g. null value of Integer prv (as alternative, you can use boolean isFirstLine flag for first line or res.isEmpty()).
public static List<Integer> receiveNumbers() {
List<Integer> res = new LinkedList<>();
Integer prv = null;
try (Scanner scan = new Scanner(System.in)) {
while (true) {
int num = scan.nextInt();
if (prv != null && prv == num)
break;
res.add(num);
prv = num;
}
}
return res;
}
import java.util.Scanner;
public class OngoingPractice {
public static void main(String[] args) {
Scanner keyboard = new Scanner(System.in);
int previous, current;
previous = keyboard.nextInt();
current = keyboard.nextInt();
while (current != previous) {
previous = current;
current = keyboard.nextInt();
}
System.out.println("Done!");
Just use an infinite while loop and break if the new int is equal to previous one. As a suggestion you should show how you tried.
Scanner sc = new Scanner(System.in);
int i;
Integer j = null;
boolean flag = false;
while(true) {
i = sc.nextInt();
if(j==null) {j=i; flag = true;}
if(j==i&&!flag) {
System.out.println("Done");
break;}
j=i;
flag = false;
}
Edited : if first one is -1, it won't work as in the comment. so I modified some.
Remember the last entered data in one variable and check it with the current data. If both matches, break the loop.
Scanner scanner = new Scanner(System.in);
String previousNumber="";
while (scan.hasNextInt()) {
int number = scan.nextInt();
if(!previousNumber.equals("") && number==Integer.parseInt(previousNumber)) {
break;
}else {
System.out.println(number);
}
previousNumber=number+"";
}
I am trying to validate my code by error checking. I want to make sure the integer people enter does not contain a letter or more.
Here is my code. I am supposed to solve this problem using a one dimensional array. I got the code working but I am having problems with adding the error checking in.
Any help would be appreciated. Thanks
public void getNumbers() {
Scanner keyboard = new Scanner(System.in);
int array[] = new int[5];
int count = 0;
int entered = 0;
int k = -1;
while (entered < array.length) {
System.out.print("Enter a number ");
int number = keyboard.nextInt();
if (10 <= number && number <= 100) {
boolean containsNumber = false;
entered++;
for (int i = 0; i < count; i++) {
if (number == array[i]) // i Or j
{
containsNumber = true;
}
}
if (!containsNumber) {
array[count] = number;
count++;
} else {
System.out.println(number + " has already been entered");
}
} else {
System.out.println("number must be between 10 and 100");
}
//what does %d do?
for (int j = 0; j < count; j++) {
System.out.printf("%d ", array[j]);
}
System.out.println();
}
}
}
I'm assuming that you would want your program to ask the user to re-enter a number if they do not input a number the first time. In this scenario you might want to try something along the lines of this:
Scanner sc = new Scanner(System.in);
System.out.println("Enter a number: ");
while(!sc.hasNextInt()) {
//print some error statement
sc.nextLine();
}
int number = sc.nextInt();
System.out.println("Number is: " + number); // to show the value of number
// continue using number however you wish
Since hasNextInt() returns a boolean determining whether or not the input is an Integer, the program will never leave the while-loop until the program can confirm that the user has entered an integer.
keyboard.nextInt() will throw a InputMismatchException if you input a String.
If you want to check whether Scanner has an integer to read, you can use keyboard.hasNextInt().
Alternatively, you can read the input as
String s = keyboard.next() which will take the input as a String, and then use s.matches(".*\\d+.*") to detect whether or not it is an integer.
UPDATE: To answer questions -
keyboard.hasNextInt() will return a boolean. So for example, after System.out.print("Enter a number"), you could have an if statement checking to see if keyboard can receive numerical input, ie. if(keyboard.hasNextInt). If this is true, that means the user has entered numerical input, and you could continue with sayingint number = keyboard.nextInt(). If it is false, you would know that the user input is non-numerical.
I have tried various techniques to check the values of user input in this method. The user should only be able to enter a '1' or a '0'. If any other input is used there should be an error message and the program exits. Any ideas? I got it to work for the first digit but not the second through the tenth.
System.out.println("Enter a ten digit binary number. Press 'Enter' after each digit. Only use one or zero. :");
binary[0] = keyboard.nextInt();
for (index = 1; index < 10; index++)
binary[index] = keyboard.nextInt();// fill array with 10 binary
// digits from user. User
// must press 'Enter' after
// each digit.
Try this:
Scanner scanner = new Scanner(System.in);
if (scanner.hasNext())
{
final String input = scanner.next();
try
{
int num = Integer.parseInt(input, 2);
}
catch (NumberFormatException error)
{
System.out.println(input + " is not a binary number.");
//OR You may exit here, if you don't want to continue
}
}
Try this code part :
import java.util.Scanner;
public class InputTest
{
public static void main(String... args) throws Exception
{
Scanner scan = new Scanner(System.in);
int[] binary = new int[10];
for (int index = 0; index < 10; index++)
{
int number = scan.nextInt();
if (number == 0 || number == 1)
{
binary[index] = number;
System.out.println("Index : " + index);
}
else
System.exit(0);
}
}
}