i have some problems here.
I want to user only can input as an integer. I have tried by many code, but still doesn't work. Btw, this is my code
import java.util.Scanner;
public class test {
public static void main (String []args){
Scanner scan = new Scanner(System.in);
int number = scan.nextInt();
}
}
When error, the message will shown as
Exception in thread "main" java.util.InputMismatchException
at java.util.Scanner.throwFor(Unknown Source)
at java.util.Scanner.next(Unknown Source)
at java.util.Scanner.nextInt(Unknown Source)
at java.util.Scanner.nextInt(Unknown Source)
at test.main(test.java:6)
Please help me (Beginner Programmer);
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
while (!scan.hasNextInt()) {
System.out.println("Input is not a number.");
scan.nextLine();
}
int number = scan.nextInt();
}
This code will check if the input is an Integer, if it is then it will continue.
Try this:
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
while (true) {
System.out.print("Enter a number -> ");
String input = sc.next();
int intInputValue = 0;
try {
intInputValue = Integer.parseInt(input);
break;
} catch (NumberFormatException ne) {
System.out.println("This is not a number");
}
}
}
This program will end when the user enter a integer input value.
Output
Such an error only occurs if the user did not enter an integer.For such a situation, you could create a try-catch block, that catches the exception, like this:
String input = sc.next();
int number = 0;
try {
number = Integer.valueOf(input);
} catch (NumberFormatException ne) {
System.out.println("Invalid input!");
}
To optimize the solution even more, put this all in a loop, and break out of it in the try-block, and keep polling for input if the user enters a bad number.
Related
public class Solution {
public static void main(String args[])
Scanner sc=new Scanner(System.in);
for(int i=0;i<5;i++){
int input1=sc.nextInt();
sc.nextLine();
String str1=sc.nextLine();
Double input2=sc.nextDouble();
}
}
}
This is my code. I only got this exception in "int" and "double" input only in for loop. IF I write it out-side of for loop it working fine. Please any one can help me solve this problem, because I am getting this error in my TCS exam.
Unfortunately your question does no give me much information, however I will try to answer anyway (need that rep). Im assuming the issue you run into is a InputMismatchException ? This is probably something to do with you trying to pass a double (i.e. 12.0) into an int. Using something like System.out.println("Enter Int Input:") can help you highlight which input type you should be providing on the line. try/catch blocks can stop the error being thrown.
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
try {
for (int i = 0; i < 5; i++) {
System.out.println("i: " + i);
System.out.println("Enter Int Value:");
int input1 = sc.nextInt();
sc.nextLine();
System.out.println("Enter String Value:");
String str1 = sc.nextLine();
System.out.println("Enter Double Value:");
Double input2 = sc.nextDouble();
}
} catch (InputMismatchException e) {
System.out.println("Invalid input entered for variable type.");
}
}
I have written a JAVA program that takes input from the user and check if the user has entered the correct thing or not. I have taken the input from the Scanner class. If the user enters an invalid character like a String, I want to display 'Invalid Input'.
public class Main {
public static void main(String[] args) {
Scanner takeInteger = new Scanner(System.in);
System.out.println("Enter a number");
int enteredNumber = takeInteger.nextInt();
}
}
Just ask the Scanner whether the next input is a valid int value, e.g.
Scanner takeInteger = new Scanner(System.in);
System.out.println("Enter a number");
while(!takeInteger.hasNextInt()) {
System.out.println("Invalid Input: " + takeInteger.next());
}
int enteredNumber = takeInteger.nextInt();
This will retry the operation until the user entered a number. If you just want a single attempt, use something like
Scanner takeInteger = new Scanner(System.in);
System.out.println("Enter a number");
if(!takeInteger.hasNextInt()) {
System.out.println("Invalid Input: " + takeInteger.next());
}
else {
int enteredNumber = takeInteger.nextInt();
// ... proceed with the input
}
You will get an Exception that is InputMismatchException when an invalid input is passed.(i.e except integer value),you can use a try-catch block to hold the exception and inform the user about the invalid input. Try block , Catch block
import java.util.*;
Scanner takeInteger = new Scanner(System.in);
System.out.println("Enter a number");
try{
int enteredNumber = takeInteger.nextInt();
}
catch(InputMismatchException e) {
System.out.println("Enter a valid input");
}
You can use Exception handling for the same.
public class Main {
public static void main(String[] args) {
Scanner takeInteger = new Scanner(System.in);
System.out.println("Enter a number");
try {
int enteredNumber = takeInteger.nextInt();
}
catch (Exception e) {
System.out.println("Invalid Input");
}
}
}
You can add a try-catch block in your program to check if the user's input is a number or not.
Scanner takeInteger = new Scanner(System.in);
System.out.println("Enter a number");
String input = takeInteger.next();
int enteredNumber;
try
{
enteredNumber = Integer.parseInt(input); // Input is a number
}
catch(NumberFormatException ex)
{
System.out.println("Wrong Input!"); // Invalid input
}
You need to call the .nextLine method of the Scanner class and then parse to the desired type.
Example:
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.println("Enter a number");
String line = sc.nextLine();
try {
int enteredNumber = Integer.parseInt(line);
System.out.println("You have entered: " + enteredNumber);
} catch (Exception e) {
System.out.println("Invalid Input");
}
}
}
Result with a number:
Enter a number
12
You have entered: 12
Result a text:
Enter a number
abcd
Invalid Input
I am taking input using java Scanner by writing following code:
import java.util.Scanner;
class main{
public static void main(String args[]){
Scanner scan=new Scanner(System.in);
System.out.println("Enter number");
int i=scan.nextInt();
}
}
but above code in throwing following exception:
Enter number
Exception in thread "main" java.util.NoSuchElementException
at java.base/java.util.Scanner.throwFor(Scanner.java:937)
at java.base/java.util.Scanner.next(Scanner.java:1594)
at java.base/java.util.Scanner.nextInt(Scanner.java:2258)
at java.base/java.util.Scanner.nextInt(Scanner.java:2212)
at main.main(main.java:7)
Tool completed with exit code 1
import java.util.Scanner;
class Input {
public static void main(String[] args) {
Scanner input = new Scanner(System.in); System.out.print("Enter an integer: ");
int number = input.nextInt();
System.out.println("You entered " + number);
}
}
Try this code.....
Here, input object of Scanner class is created. Then, the nextInt() method of the Scanner class is used to get integer input from the user.
To get long, float, double and Stringinput from the user, you can use nextLong(), nextFloat(), nextDouble() and next() methods respectively.
You are almost there. One note is you expect int value and if user enter e.g. string, then you get an exception.
public static int askIntNumber(Scanner scan) {
while(true) {
try {
System.out.print("Enter number: ");
return scan.nextInt();
} catch (Exception e) {
System.err.println("This is not an integer number");
}
}
You should try this:
import java.util.Scanner;
public class main {
public static void main(String[]args) {
Scanner sc=new Scanner(System.in);
System.out.println("Enter number: ");
int i=sc.nextInt();
}
}
The block of code sc.nextInt scans the entire input and then puts it into play. This should solve your problem.
i run the code it gives an these errors:
Exception in thread "main" java.util.InputMismatchException
at java.util.Scanner.throwFor(Unknown Source)
at java.util.Scanner.next(Unknown Source)
at java.util.Scanner.nextInt(Unknown Source)
at java.util.Scanner.nextInt(Unknown Source)
at Main.start(Main.java:15)
at Main.main(Main.java:9)
this code is ment to take the input out of the main then put the data in the save and let the text you add to the file safe the words and keeps updating but i keep getting errors whit wrong user input if some1 can help me fix the error i would apprecieet it here the code there in the directionary and the files are connect (no package needed)
Main java
import java.util.Scanner;
public class Main{
Save option = new Save();
public static void main(String[] args) {
Main main = new Main();
main.start();
}
public void start(){
Scanner scanner = new Scanner(System.in);
System.out.println("1. Add random words to file");
int result = scanner.nextInt();
scanner.nextLine();
if (result == 1 ) {
try{
String safeWordsString = "";
System.out.println("Type some words");
safeWordsString = scanner.nextLine();
option.safeWords(safeWordsString);
} catch (Exception e) {
start();
}
}
}
}
Save java
import java.util.*;
import java.io.*;
public class Save
{
public void safeWords(String saveTekst)
{
try{
//USER INPUT BINNEHALEN
// Scanner userInput = new Scanner(System.in);
// System.out.println("Welke regel wil je toevoegen");
// String regel = userInput.nextline();
// ORIGINELE DATA VERZAMELEN
File original = new File("test.txt");
Scanner scanner = new Scanner(original);
StringBuilder temp = new StringBuilder();
while (scanner.hasNext()){
temp.append(scanner.nextLine() + "\n");
}
// NIUEWE DATA APPENDEN
PrintWriter pw = new PrintWriter(original);
pw.println(temp);
pw.println(new Date() + " " + saveTekst);
pw.close();
System.out.println("End");
} catch (Exception e) {
System.out.println("Error");
}
}
}
You should accept your input as String
public void start(){
Scanner scanner = new Scanner(System.in);
System.out.println("1. Add random words to file");
String result = scanner.nextLine();
if("1".equals(result)){
...
}
}
In the program itself, you are trying to get the integer from Scanner..
if the integer is 1, then you are proceeding further to add random words, it is just like choosing an option from list of options..
Here you have only 1 option, so please choose it first(type 1 and enter), then proceed further to add your random words..
I need int num to only accept numbers. If I input letters I get an error. Is there a way to immediately flag letters, or do I have to take num in as a string and run loops?
import java.util.Scanner;
public class Test
{
public static void main(String[] args)
{
Scanner input = new Scanner(System.in);
System.out.println("Input a number.");
int num = input.nextInt();
}
}
You must use Scanner.hasNextInt():
It Returns true if the next token in this scanner's input can be interpreted as an int value in the default radix using the nextInt() method. The scanner does not advance past any input.
public static void main(String[] args)
{
System.out.println("Input a number.");
Scanner sc = new Scanner(System.in);
System.out.print("Enter number 1: ");
while (!sc.hasNextInt()) sc.next();
int num = sc.nextInt();
System.out.println(num);
}
You probably want to do something like this:
import java.util.InputMismatchException
import java.util.Scanner;
public class Test {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.println("Input an integer.");
int num = 0; // or any other default value
try {
num = input.nextInt();
} catch (InputMismatchException e) {
System.out.println("You should've entered an integer like I told you. Fool.");
} finally {
input.close();
}
}
}
If the user enters something that is not an integer, the code within the catch block will be executed.