How to check if user input is not an int value

Question

I need to check if a user input value is not an int value  I ve tried different combinations of what I know but I either get nothing or random errors  For example   If the user inputs  adfadf 1324  it ll raise a warning message     What I have             Initialize a Scanner to read input from the command line        Scanner sc   new Scanner System in          int integer  smallest   0  input         boolean error   false          System out print  Enter an integer between 1-100             range   sc nextInt            if  sc hasNextInt                 error   true            System out println  Invalid input               System out print  How many integers shall we compare   Enter an integer between 1-100                sc next                  while error              for int ii   1  ii  lt   integer  ii                                         end for loop               System out println  The smallest number entered was      smallest

User · Answer

you have following errors which in turn is causing you that exception, let me explain it

this is your existing code:

if(!scan.hasNextInt()) {
        System.out.println("Invalid input!");
        System.out.print("Enter an integer: ");
        usrInput= sc.nextInt();
    }

in the above code if(!scan.hasNextInt()) will become true only when user input contains both characters as well as integers like your input adfd 123.

but you are trying to read only integers inside the if condition using usrInput= sc.nextInt();. Which is incorrect,that's what is throwing Exception in thread "main" java.util.InputMismatchException.

so correct code should be

 if(!scan.hasNextInt()) {
            System.out.println("Invalid input!");
            System.out.print("Enter an integer: ");
            sc.next(); 
            continue;
        }

in the above code sc.next() will help to read new input from user and continue will help in executing same if condition(i.e if(!scan.hasNextInt())) again.

Please use code in my first answer to build your complete logic.let me know if you need any explanation on it.

User · Answer

Try this one       for                if   sc hasNextInt                  System out println   enter only integers                   sc next       discard             continue                    choose   sc nextInt            if  choose  gt   0                System out print  no problem with input               else               System out print  invalid inputs                   break

User · Answer

Maybe you can try this  int function    Scanner input   new Scanner System in      System out print  quot Enter an integer between 1-100   quot       int range  while true          if input hasNextInt            range   input nextInt        if 0 lt  range  amp  amp  range  lt   100          break      else         continue            input nextLine       Comsume the garbage value     System out println  quot Enter an integer between 1-100  quot      return range

User · Answer

Taken from a related post   public static boolean isInteger String s        try            Integer parseInt s          catch NumberFormatException e             return false                only got here if we didn t return false     return true

User · Answer

Simply throw Exception if input is invalid  Scanner sc new Scanner System in   try     System out println  Please input an integer        nextInt will throw InputMismatchException     if the next token does not match the Integer     regular expression  or is out of range   int usrInput sc nextInt      catch InputMismatchException exception        Print  This is not an integer      when user put other than integer   System out println  This is not an integer

User · Answer

This is to keep requesting inputs while this input is integer and find whether  it is odd or even else it will end   int counter   1      System out println  Enter a number         Scanner OddInput   new Scanner System in           while OddInput hasNextInt                 int Num   OddInput nextInt                if  Num  2  0                   System out println  Number     Num     is Even                    System out println  Enter a number                               else                   System out println  Number     Num     is Odd                    System out println  Enter a number                                             System out println  Program Ended

User · Answer

try this code  updated    Scanner scan   null         int range  smallest   0  input        for               boolean error false          scan   new Scanner System in           System out print  Enter an integer between 1-100                     if  scan hasNextInt                      System out println  Invalid input                                           continue                         range   scan nextInt                if range  lt  1                    System out println  Invalid input                     error true                        if error                      do nothing                   else                  break                                    for int ii   1  ii  lt   range  ii                  scan   new Scanner System in               System out print  Enter value     ii                       if  scan hasNextInt                      System out println  Invalid input                     ii--                  continue

[java] How to check if user input is not an int value

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