java - 填充对象数组时 readInt() 上的扫描仪错误

Question

我正在尝试迭代对象数组，并使用扫描仪设置其中一个实例变量。这是引发错误的代码:

 public void populate(){
    int participantID = 0;
    Scanner pop = new Scanner(System.in);
    while(participantID < participants.length){
        participants[participantID] = new Participant();
        System.out.println("Time in Seconds?");
        int time = pop.nextInt();
        participants[participantID].setTotalTime(time);
        participantID++;
    }
    pop.close();
}

这会导致 int time = pop.nextInt(); 行出现错误。即

Exception in thread "main" java.util.NoSuchElementException
Time in Seconds?    at java.util.Scanner.throwFor(Scanner.java:862)

这真的让我很困惑，因为这个方法工作得很好:

    public void create(){
    Scanner scan = new Scanner(System.in);

    System.out.println("What is the name of the triathlon?");
    raceName = scan.nextLine();

    System.out.println("How many participants were there?");
    participants = new Participant[scan.nextInt()];

    scan.close();
}

<小时/>

应用程序.java

    public class Application {
    public static void main(String[] args){
        Race mainRace = new Race();
        mainRace.create();
        System.out.println(mainRace.toString());
        mainRace.populate();
        System.out.println(mainRace.toString());
    }
}

Race.java

import java.util.Scanner;

public class Race {
    private String raceName;
    private Participant participants[];

    public Race(){

    }

    public String toString() {
        return "Race{" +
                "raceName='" + raceName + '\'' +
                ", participants=" + participants.length +
                '}';
    }

    public void create(){
        Scanner scan = new Scanner(System.in);

        System.out.println(Colours.getAnsiYellow() + "What is the name of the triathlon?" + Colours.getAnsiReset());
        raceName = scan.nextLine();

        System.out.println(Colours.getAnsiYellow() + "How many participants were there?" + Colours.getAnsiReset());
        participants = new Participant[scan.nextInt()];

        scan.close();
    }

    public void populate(){
        int participantID = 0;
        Scanner pop = new Scanner(System.in);
        while(participantID < participants.length){
            participants[participantID] = new Participant();

            System.out.println(Colours.getAnsiYellow() + "Time in Seconds?" + Colours.getAnsiReset());
            int time = pop.nextInt();
            participants[participantID].setTotalTime(time);
            System.out.println(participants[participantID]);
            participantID++;

        }
        pop.close();

    }

}

参与者.java

public class Participant {
    private int id;
    private int runTime;
    private int swimTime;
    private int bikeTime;
    private int totalTime;

    public Participant(){
    }

    public int getTotalTime() {
        return totalTime;
    }

    public void setTotalTime(int totalTime) {
        this.totalTime = totalTime;
    }
}

颜色.java

public class Colours {
    public static final String ANSI_RESET = "\u001B[0m";
    public static final String ANSI_YELLOW = "\u001B[33m";

    public static String getAnsiReset() {
        return ANSI_RESET;
    }


    public static String getAnsiYellow() {
        return ANSI_YELLOW;
    }

}

Answer 1

问题不在于您的 populate 方法。问题是，您在 create 方法中创建的 Participant 数组在您关闭扫描程序后将不再存在。因此，请在 create 方法中调用 populate 方法，而不是在 Application 类中调用。

主要:

public class Application {
    public static void main(String[] args) {
        Race mainRace = new Race();
        mainRace.create();
        System.out.println(mainRace.toString());
    }
}

创建方法:

public void create() {

    Scanner scan = new Scanner(System.in);

    System.out.println(Colours.getAnsiYellow() + "What is the name of the triathlon?" + Colours.getAnsiReset());
    raceName = scan.nextLine();

    System.out.println(Colours.getAnsiYellow() + "How many participants were there?" + Colours.getAnsiReset());
    participants = new Participant[scan.nextInt()];

    populate(); 

    scan.close();


}