How can I clear the Scanner buffer in Java

Question

I have something like this       Scanner in new Scanner System in       int rounds   0      while  rounds  lt  1    rounds  gt  3            System out print  How many rounds              if  in hasNextInt                  rounds   in nextInt              else               System out println  Invalid input  Please try again                 System out println                         Clear buffer           System out print rounds   rounds       How can I clear the buffer   Edit  I tried the following  but it does not work for some reason   while in hasNext        in next

User · Accepted Answer

You can t explicitly clear Scanner s buffer  Internally  it may clear the buffer after a token is read  but that s an implementation detail outside of the porgrammers  reach

User · Answer

Use the following command    in nextLine      right after  System out println  Invalid input  Please Try Again     System out println      or after the following curly bracket  where your comment regarding it  is    This command advances the scanner to the next line  when reading from a file or string  this simply reads the next line   thus essentially flushing it  in this case  It clears the buffer and readies the scanner for a new input  It can  preferably  be used for clearing the current buffer when a user has entered an invalid input  such as a letter when asked for a number     Documentation of the method can be found here  http   docs oracle com javase 7 docs api java util Scanner html nextLine    Hope this helps

User · Answer

Other people have suggested using in nextLine   to clear the buffer  which works for single-line input  As comments point out  however  sometimes System in input can be multi-line   You can instead create a new Scanner object where you want to clear the buffer if you are using System in and not some other InputStream   in   new Scanner System in    If you do this  don t call in close   first  Doing so will close System in  and so you will get NoSuchElementExceptions on subsequent calls to in nextInt    System in probably shouldn t be closed during your program    The above approach is specific to System in  It might not be appropriate for other input streams    If you really need to close your Scanner object before creating a new one  this StackOverflow answer suggests creating an InputStream wrapper for System in that has its own close   method that doesn t close the wrapped System in stream  This is overkill for simple programs  though

User · Answer

This should fix it     Scanner in new Scanner System in       int rounds   0      while  rounds  lt  1    rounds  gt  3            System out print  How many rounds              if  in hasNextInt                  rounds   in nextInt              else               System out println  Invalid input  Please try again                 in next       -- gt important             System out println                         Clear buffer           System out print rounds   rounds

User · Answer

Try this   in nextLine      This advances the Scanner to the next line

[java] How can I clear the Scanner buffer in Java?

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