Java String Scanner input does not wait for info, moves directly to next statement. How to wait for info? [duplicate]

Question

I am writing a simple program that prompts a user to enter a number of students, then asks the user to enter each student's name and score in order to determine which student has the highest score.

I have written the program code and it compiles. First line asks for a number of students and waits for input. The second line is supposed to ask for a student name and wait for input, then a third line should print ans ask for that student's score, and wait for input but after the second line prints, the third line is immediately called (2nd line does not wait for input) and then I get a runtime error when trying to enter the requested information after the third line.

How do I adjust the code so that the second line prints and waits for a string to be entered before printing the third line?

import java.util.Scanner;  public class HighestScore {     public static void main(String[] args) {         Scanner input = new Scanner(System.in);          System.out.print("Enter the number of students: ");         int numOfStudents = input.nextInt();          System.out.print("Enter a student's name: ");         String student1 = input.nextLine();          System.out.print("Enter that student's score: ");         int score1 = input.nextInt();          for (int i = 0; i <= numOfStudents - 1; i++) {              System.out.println("Enter a student's name: ");             String student = input.nextLine();              System.out.println("Enter that student's score: ");             int score = input.nextInt();              if (score > score1) {             student1 = student;             score1 = score;             }         }         System.out.println("Top student " +         student1 + "'s score is " + score1);     } } 

Answer 1

That's why I don't didn't like using a Scanner, because of this behavior. (Once I understood what was happening, and felt comfortable with it, I like Scanner a lot).

What is happening is that the call to nextLine() first finishes the line where the user enters the number of students. Why? Because nextInt() reads only one int and does not finish the line.

So adding an extra readLine() statement would solve this problem.

System.out.print("Enter the number of students: "); int numOfStudents = input.nextInt();  // Skip the newline input.nextLine();  System.out.print("Enter a student's name: "); String student1 = input.nextLine(); 

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As I already mentioned, I didn't like using Scanner. What I used to do was to use a BufferedReader. It's more work, but it's slightly more straightforward what is actually happening. Your application would look like this:

BufferedReader input = new BufferedReader(new InputStreamReader(System.in));  System.out.println("Enter the number of students: "); int numOfStudents = Integer.parseInt(input.readLine());  String topStudent = null; int topScore = 0; for (int i = 0; i < numOfStudents; ++i) {     System.out.print("Enter the name of student " + (i + 1) + ": ");     String student = input.nextLine();      // Check if this student did better than the previous top student     if (score > topScore)     {          topScore = score;          topStudent = student;     } } 

Answer 2

    System.out.print("Enter the number of students: ");     int numOfStudents = input.nextInt();     // Eat the new line     input.nextLine();     System.out.print("Enter a student's name: ");     String student1 = input.nextLine();