java - 为什么我的 for 循环在使用 (scanner).nextLine(); 时一次打印 2 个提示

Question

我的 while 或 for 循环是否偶然出现问题，或者我遗漏了什么？第一次运行效果很好，但第二次我得到了这个:

Enter course NAME: class name
Enter course HOURS: 4
Enter course GRADE: 4.0
You have entered class: jeff graves, class hours: 4 and, class grade 4.0
Do you want to continue:
y
Enter course NAME: Enter course HOURS: 

使用 (scanner).next(); 工作得很好，但是我只能从用户那里获取一个单词，并且当它滚动时，它会从 nextInt 抛出一个错误。

   public class GetGrades { //open class GetGrades

    public static void main(String[] args)  {
/**creating new instance of scanner named input to read user input*/
        Scanner input = new Scanner(System.in);  // create new instance of scanner object
        boolean repeat = true;  //boolean value for while loop holding array input
        String s;  // create string to store user input value for exiting loops
/** create 3 arrays to store course name, hours, and grades*/
        String[] name = new String[20]; //type string array for class name
        int[] hours = new int[20]; // type int array for class hours
        float[] grade = new float[20]; //type float array for class grade


        outerloop:  // set break point for nested for loops exit on user input 
            while(repeat != false)  {// while loop with boolean value to let user exit array input
        for (int i=0; i<name.length; i++)  { //for loop for name array

            System.out.print("Enter course NAME: "); //prompt user for input
            name[i] = input.nextLine(); //read next line value and store in array name
            System.out.print("Enter course HOURS: "); //prompt user for input
            hours[i] = input.nextInt(); //read the next int and store in array hours
            System.out.print("Enter course GRADE: "); //prompt user for input
            grade[i] = input.nextFloat(); //read the next float value and store in array grade

        /**Print line to console summing um what the user has entered*/
            System.out.println("You have entered class: " + name[i] + ", class hours: " + hours[i] + 
                    " and, class grade " + grade[i]);

/**prompt user if wanted to enter more grades, break loop on n or N*/
            System.out.println("Do you want to continue:");
            s = input.next();
            if ( s.equals("y") || s.equals("Y"))  { //open if statement
                repeat = true;
            } else  { //close if and open else
                break outerloop;
            }  //close else statement


          }//close for loop with i as count
        }//close while

Answer 1

input.next() 将读取下一个单词。 input.nextLine() 将一直读取，直到您下次按 Enter 键。

这意味着当您输入“y”并按回车键时，您既输入了单词“y”，也输入了下一个回车键，同时填写了两个提示并导致写入下一个提示.

当您要求继续时，您只需将 next() 替换为 nextLine() 即可:

        System.out.println("Do you want to continue:");
        s = input.next();

变成了

        System.out.println("Do you want to continue:");
        s = input.nextLine(); 

从而读取“y”和回车键。下一个提示现在可以自由接受新输入。