java - 从方法创建另一个类的实例并将其输出添加到 map

Question

我是 Java 的新手，正在构建一个小型提醒应用程序，让人们跟踪 Activity 。

该应用程序有 2 个类 Activity 和 WhatsOn。

我试图了解如何在 WhatsOn 中的 addActivity 方法范围内创建 Activity.java 类的实例。 java类，它将输出通过管道传输到创建的名为 activities 的 map 中。

public class WhatsOn {
    //instance variables for WhatsOn class
    private static String today;
    private static int nextId;
    private Map<Integer, Activity> activities;

    // the constructor for the WhatsOn class
    public WhatsOn(Map<Integer, Activity> activities) {
        this.activities = activities;
        today = "010117";
        nextId = 1;
    }

    // This method should create an instance of Activity class  and then add it to the map referenced by the current value of nextId as the key
    public void addActivity (String aName, String aDate, String aTime) {
    // method required
    }
}

Activity .java

public class Activity {

    private String name;
    private String date;
    private String time;

    //constructor
    Activity(String name, String date, String time) {
        this.name = name;
        this.date = date;
        this.time = time;
    }

    //getters and setters
    public void setDate(String aDate) {
        this.date = aDate;
    }

    public void setTime(String aTime) {
        this.time = aTime;
    }

    public void setName(String aName) {
        this.name = aName;
    }

    public String getDate() {
        return this.date;
    }

    public String getTime() {
        return this.time;
    }

    public String getName() {
        return this.name;
    }
}

Answer 1

在您的 add 方法中，创建一个 Activity 实例。然后将其添加到您的 map 。最后增加nextId。它应该看起来像这样:

public void addActivity (String aName, String aDate, String aTime) {
    Activity actToAdd = new Activity(aName, aDate, aTime); //create an instance of Activity
    activities.put(nextId, actToAdd); //Add this intance to your Map
    nextId++; //increase the nextId
}