Question

如何从两个单独的类中将一个数组添加到另一个数组，然后从主类访问它？总列表在打印时显示[]，但第二类显示所有名称。

public class Main {

    private static Plane fly = new Plane();
    private static Secondclass sec = new Secondclass();

    public static void main(String[] args) {

        sec.addPassenger("John");
        sec.addPassenger("Fatso");
        sec.addPassenger("Lisa");
        sec.addPassenger("Mike");
        sec.addPassenger("Randy");
        sec.addPassenger("Jonathan");

        System.out.println("Total list is "+fly.getTotalList());
        System.out.println("Second class is " + sec.getPassengerNames());
    }
}
________________________________________

public class Plane {
    private Secondclass sec;
    private ArrayList<String> totalList;

    public Plane() {
        this.totalList = new ArrayList<String>();
    }

    public void addTotalList() {
        this.totalList.addAll(sec.getPassengerNames());
    }

    public ArrayList<String> getTotalList() {
        return totalList;
    }

}
________________________________________

public class Secondclass{
    private ArrayList<String> passengerNames;

    public Secondclass() {
        this.passengerNames = new ArrayList<String>();
    }

    public ArrayList<String> getPassengerNames() {
        return passengerNames;
    }

    public void addPassenger(String name){
        passengerNames.add(name);
    }
}

Answer 1

您的代码中缺少两个重要的行。

用对象SecondClass的引用作为参数编写构造函数Plane。
在sec对象中添加值之后，使用sec对象作为参数传递来创建构造函数。

调用plane.addTotalList（）

import java.util.ArrayList;

public class Main {
private static Plane fly;
private static Secondclass sec = new Secondclass();

public static void main(String[] args) {

    sec.addPassenger("John");
    sec.addPassenger("Fatso");
    sec.addPassenger("Lisa");
    sec.addPassenger("Mike");
    sec.addPassenger("Randy");
    sec.addPassenger("Jonathan");

    fly = new Plane(sec);
    fly.addTotalList();

    System.out.println("Total list is " + fly.getTotalList());
    System.out.println("Second class is " + sec.getPassengerNames());
}
}

class Plane {
private Secondclass sec;
private ArrayList<String> totalList;

public Plane(Secondclass sec) {
    this.sec = sec;
    this.totalList = new ArrayList<String>();
}

public void addTotalList() {
    this.totalList.addAll(sec.getPassengerNames());
}

public ArrayList<String> getTotalList() {
    return totalList;
}

}

class Secondclass {
private ArrayList<String> passengerNames;

public Secondclass() {
    this.passengerNames = new ArrayList<String>();
}

public ArrayList<String> getPassengerNames() {
    return passengerNames;
}

public void addPassenger(String name) {
    passengerNames.add(name);
}
}`

输出：

总列表为[约翰，法索，丽莎，迈克，兰迪，乔纳森] 第二类是[约翰，法索，丽莎，迈克，兰迪，乔纳森]

从另一个类访问列表

1 个答案: