Using scanner.nextLine() [duplicate]

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 

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// 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.

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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().

Answer 1

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.