java - 循环数组列表并将与两个数组列表匹配的值添加到新的数组列表中

Question

我正在尝试制作一个将客户兴趣与假期的各个方面相匹配的程序，我有一个假期数组列表和一个客户兴趣字符串数组列表，我想创建一个新的数组列表，它将添加两者中包含的所有元素。这就是我所拥有的，但它出现了空指针异常，有什么想法我哪里出错了吗？调试器指向不相交的“int c1size = c1.size();”相关代码部分...

主要...

ClientExt1 marina = new ClientExt1("Marina",14321,"marina.calder1@btinternet.com");
ArrayList<String> interests = new ArrayList<>();
interests.add("History");
interests.add("Music");
marina.setInterests(interests);
holidaySeller.getHolidayMatches(marina);

客户端...

public class ClientExt1 {

private String name;
private int id;
private String email;
private HolidayExt1 holidayBooked;
private ArrayList<String> interests;

public ClientExt1(String name, int id, String email){
    this.name=name;
    this.id=id;
    this.email=email;


}

public void setInterests(ArrayList interests) {
    this.interests=interests;
}

public ArrayList<String> getInterests(){
    return interests;

公司类别...

public class CompanyExt1 {
    protected ArrayList<StaffExt1> staffMembers;                  
    protected ArrayList<HolidayExt1> holidays;
    protected ArrayList<GuideExt1> holidayGuides;
    protected ArrayList<AdventureExt1> adventureHolidays;
    protected ArrayList<CultureExt1> cultureHolidays;
    private ArrayList<String> matchedHolidays;


    public ArrayList<String> findHolidayMatch(ClientExt1 client) {
        ArrayList interests = client.getInterests();
        int i;
        for (i = 0; i < holidays.size() && i< interests.size(); i++) {
            if (!Collections.disjoint(holidays.get(i).getAspects(), interests)) {
                matchedHolidays.add(holidays.get(i).getName());

            }
        }
        return matchedHolidays;
    }

    public void getHolidayMatches(ClientExt1 client){
        System.out.println(client.getName() + ", the holidays recommended to you based on your interests from this company are:" + findHolidayMatch(client));
    }
}

Answer 1

您需要在使用之前初始化 holidays，并在 findHolidayMatch 中向其添加值之前初始化 matchedHolidays

我实际上会将matchedHolidays设置为局部变量而不是类成员，因为它仅在findHolidayMatch方法的范围内使用。