Question

我的while或for循环中是否存在问题，或者我错过了什么？第一次运行正常，但在第二次我得到这个：

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();可以正常工作，但是我只能从用户那里取一个单词，它会在翻转时从nextInt中抛出错误。

   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()会读下一个字。 input.nextLine()会在下次按Enter键时读取。

这意味着当你写“y”并点击回车时，你输入了一个单词“y”，以及下一个输入，同时填写两个提示并导致下一个提示被写入

当您要求继续时，您只需将next()替换为nextLine()：

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

变为

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

从而读取“y”和输入。现在，下一个提示可以自由接受新输入。

Answer 2

输入成绩时，例如12.3并输入“input.nextFloat（）;”只会选择“12.3”而不是“输入”，所以“输入”将由下一个扫描仪拍摄。

在我看来，

首先，将“s = input.next（）”更改为“s = input.nextLine（）”，但它将采用先前扫描仪的“enter”“grade [i] = input.nextFloat（）;” ，所以，第二，把它作为条件放入while循环。像这样

while((s = input.nextLine()).equals("")) {}

因此，它不会停止直到获得期望输入。

试试这个..

System.out.print("Do you want to continue:");
while((s = input.nextLine()).equals("")) {}
if (s.equals("y") || s.equals("Y")) { // open if statement
    repeat = true;
} else { // close if and open else
    break outerloop;
} // close else statement

为什么我的for循环打印使用（扫描仪）.nextLine（）;

2 个答案: