Using scanner nextLine

Question

I have been having trouble while attempting to use the nextLine   method from java util Scanner    Here is what I tried   import java util Scanner   class TestRevised       public void menu             Scanner scanner   new Scanner System in            System out print  Enter a sentence  t            String sentence   scanner nextLine             System out print  Enter an index  t            int index   scanner nextInt             System out println   nYour sentence  t    sentence           System out println  Your index  t    index             Example  1  This example works as intended  The line String sentence   scanner nextLine    waits for input to be entered before continuing on to System out print  Enter an index  t      This produces the output   Enter a sentence    Hello  Enter an index  0  Your sentence   Hello  Your index  0        Example  2 import java util Scanner   class Test       public void menu             Scanner scanner   new Scanner System in            while  true                System out println   nMenu Options n                System out println   1  - do this                System out println   2  - quit                 System out print  Please enter your selection  t                int selection   scanner nextInt                 if  selection    1                    System out print  Enter a sentence  t                    String sentence   scanner nextLine                     System out print  Enter an index  t                    int index   scanner nextInt                     System out println   nYour sentence  t    sentence                   System out println  Your index  t    index                             else if  selection    2                    break                                    Example  2  This example does not work as intended  This example uses a while loop and and if - else structure to allow the user to choose what to do  Once the program gets to String sentence   scanner nextLine     it does not wait for input but instead executes the line System out print  Enter an index  t      This produces the output   Menu Options   1  - do this  2  - quit  Please enter your selection     1 Enter a sentence    Enter an index     Which makes it impossible to enter a sentence     Why does example  2 not work as intended  The only difference between Ex  1 and 2 is that Ex  2 has a while loop and an if-else structure  I don t understand why this affects the behavior of scanner nextInt

User · Answer

Don t try to scan text with nextLine    AFTER using nextInt   with the same scanner  It doesn t work well with Java Scanner  and many Java developers opt to just use another Scanner for integers  You can call these scanners scan1 and scan2 if you want

User · Answer

I think your problem is that  int selection   scanner nextInt      reads just the number  not the end of line or anything after the number   When you declare  String sentence   scanner nextLine      This reads the remainder of the line with the number on it  with nothing after the number I suspect    Try placing a scanner nextLine    after each nextInt   if you intend to ignore the rest of the line

User · Answer

or  int selection   Integer parseInt scanner nextLine

User · Answer

It s because when you enter a number then press Enter  input nextInt   consumes only the number  not the  end of line   Primitive data types like int  double etc do not consume  end of line   therefore the  end of line  remains in buffer and When input next   executes  it consumes the  end of line  from buffer from the first input  That s why  your String sentence   scanner next   only consumes the  end of line  and does not wait to read from keyboard   Tip  use scanner nextLine   instead of scanner next   because scanner next   does not read white spaces from the keyboard   Truncate the string after giving some space from keyboard  only show string before space

User · Answer

Rather than placing an extra scanner nextLine   each time you want to read something  since it seems you want to accept each input on a new line  you might want to instead changing the delimiter to actually match only newlines  instead of any whitespace  as is the default   import java util Scanner   class ScannerTest       public static void main String   args            Scanner scanner   new Scanner System in           scanner useDelimiter    n             System out print  Enter an index              int index   scanner nextInt             System out print  Enter a sentence              String sentence   scanner next             System out println   nYour sentence      sentence           System out println  Your index      index             Thus  to read a line of input  you only need scanner next   that has the same behavior delimiter-wise of next Int  Double         The difference with the  nextLine   every time  approach  is that the latter will accept  as an index also  lt space gt 3  3 lt space gt  and 3 lt space gt whatever while the former only accepts 3 on a line on its own

[java] Using scanner.nextLine()

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