Java：Scanner和ArrayList

Question

我正在进行编码练习以模拟手机中的联系人列表，您可以搜索现有联系人并从系统输入添加新联系人，但是，我遇到了一些处理扫描仪的问题而且不知道原因：（I真的很感谢你的帮助，所以提前谢谢！）

这是我的代码： 首先是联系人课程：

public class Contacts {

private String contactName;
private String phoneNumber;

public Contacts(){

}

public Contacts(String contactName, String phoneNumber) {
    this.contactName = contactName;
    this.phoneNumber = phoneNumber;
}

public String getContactName() {
    return contactName;
}

public String getPhoneNumber() {
    return phoneNumber;
}
}

然后我创建了一个MobilePhone类来保存联系人ArrayList，使用addContact（）和searchContactByName（）方法：

public class MobilePhone {

private ArrayList<Contacts> contactList = new ArrayList<Contacts>();

//searchContactByName() method takes the contact name you want to search and 
//return the contact object with that contact name if it's in the list, and return null if the contact is not on the list

public Contacts searchContactByName(String contactName){
        Contacts returnContact = new Contacts();
        boolean contactExist = false;
        for(int i = 0; i < contactList.size(); i++){
            if(contactList.get(i).getContactName() == contactName){
                System.out.println("Contact " + contactName + " found");
                contactExist = true;
                returnContact = contactList.get(i);
                break;
            }
        }

        if(contactExist == true){
            return returnContact;
        }else{
            System.out.println("not found");
            return null;
        }
    }

//addContact2() method use the searchContactByName() method to make sure
//that the contact you add does not already exists in the list

public void addContact2(String contactName, String phoneNumber){
        Contacts newContact = new Contacts(contactName,phoneNumber);
        if(searchContactByName(contactName) != null){
            System.out.println("This contact is already in the contact list.");
        }else{
            contactList.add(newContact);
            System.out.println(contactName + " has been added to the list");
        }
    }

但是，在我尝试实现该功能的主要方法中：

public class TestMain {
    public static Scanner myScanner = new Scanner(System.in);
    public static void main(String[] args) {

    MobilePhone jolenePhone = new MobilePhone();
    //First add a contact object with contactName "Rish" in the list:
    jolenePhone.addContact2("Rish","1234");

    //Then use searchContactByName() function to search the contact object with name "Rish" in the list:
    jolenePhone.searchContactByName("Rish");
    }
    }

这可以正常使用控制台的输出：

但是，如果我使用扫描仪功能：

MobilePhone jolenePhone = new MobilePhone();
        //First add a contact object with contactName "Rish" in the list:

        jolenePhone.addContact2("Rish","1234");
        System.out.println("Please enter search name: ");
        String searchName = myScanner.nextLine();
        jolenePhone.searchContactByName(searchName);

然后，我通过控制台输入的联系人名称“Rish”找不到searchFunction：

我不明白为什么我会直接传递contactName参数“Rish”，或者我使用scanner.nextLine（）函数从控制台输入，我在这里错过了什么？< / p>

Answer 1

将if(contactList.get(i).getContactName() == contactName)改为= equals()。 ==用于引用相等，equals用于对象相等。

Answer 2

请勿使用==使用equals()或equalsIgnoreCase()来忽略案例敏感