How to check the input is an integer or not in Java

Question

In my program I want an integer input by the user  I want an error message to be show when user inputs a value which is not an integer  How can I do this   My program is to find area of circle  In which user will input the value of radius  But if user inputs a character I want a message to be shown saying Invalid Input    This is my code   int radius  area  Scanner input new Scanner System in   System out println  Enter the radius  t    radius input nextInt    area 3 14 radius radius  System out println  Area of circle  t  area

User · Answer

String input               int inputInteger   0          BufferedReader br      new BufferedReader new InputStreamReader  System in             System out println  Enter the radious              try               input   br readLine                inputInteger   Integer parseInt input             catch  NumberFormatException e                System out println  Please Enter An Integer                e printStackTrace              catch  IOException e                e printStackTrace                      float area    float   3 14 inputInteger inputInteger           System out println  Area     area

User · Answer

You can try this way   String input        try      int x   Integer parseInt input          You can use this method to convert String to int  But if input       is not an int  value then this will throws NumberFormatException      System out println  Valid input      catch NumberFormatException e       System out println  input is not an int value           Here catch NumberFormatException       So input is not a int

User · Answer

Using Integer parseIn String   you can parse string value into integer  Also you need to catch exception in case if input string is not a proper number   int x   0   try              x   Integer parseInt  100       Parse string into number   catch  NumberFormatException e        e printStackTrace

User · Answer

You can use try-catch block to check for integer value  for eg   User inputs in form of string  try      int num Integer parseInt  Some String Input      catch NumberFormatException e        If number is not integer you wil get exception and exception message will be printed   System out println e getMessage

User · Answer

If the user input is a String then you can try to parse it as an integer using parseInt method  which throws NumberFormatException when the input is not a valid number string   try        int intValue   Integer parseInt stringUserInput      NumberFormatException e        System out println  Input is not a valid integer

User · Answer

If you are getting the user input with Scanner  you can do   if yourScanner hasNextInt          yourNumber   yourScanner nextInt        If you are not  you ll have to convert it to int and catch a NumberFormatException   try      yourNumber   Integer parseInt yourInput    catch  NumberFormatException ex          handle exception here

[java] How to check the input is an integer or not in Java?

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