问题

目标 - 编写一个名为PhoneBookEntry的类，该类具有存储人名和电话号码的字段。该类应包含一个构造函数以及适当的访问器和修改器方法。然后编写一个程序，创建至少五个PhoneBookEntry对象，并将它们存储在一个ArrayList中。使用循环来显示ArrayList中每个对象的内容。

代码 -

package phonebook;
import java.util.ArrayList;

public class PhoneBookEntry {
    private String personName;
    private int phoneNumber;

    public PhoneBookEntry(String personName, int phoneNumber) {
        this.personName = personName;
        this.phoneNumber = phoneNumber;
    }

    public String getPersonName() {
        return personName;
    }

    public void setPersonName(String personName) {
        this.personName = personName;
    }

    public int getPhoneNumber() {
        return phoneNumber;
    }

    public void setPhoneNumber(int phoneNumber) {
        this.phoneNumber = phoneNumber;
    }

    @Override
    public String toString() {
        return "Name: " + personName + ", Phone Number: " + phoneNumber;
    }

    public static void main(String[] args) {
        ArrayList<PhoneBookEntry> phoneBook = new ArrayList<PhoneBookEntry>();

        PhoneBookEntry Jack = new PhoneBookEntry("Jack Daniel", 6784395823L);
        PhoneBookEntry Dave = new PhoneBookEntry("Dave Daniel", 3662631363L);
        PhoneBookEntry John = new PhoneBookEntry("John Daniel", 4046428642L);
        PhoneBookEntry Judy = new PhoneBookEntry("Judy Daniel", 2329529142L);
        PhoneBookEntry Jennifer = new PhoneBookEntry("Jennifer Daniel", 5631248246L);

        phoneBook.add(Jack);
        phoneBook.add(Dave);
        phoneBook.add(John);
        phoneBook.add(Judy);
        phoneBook.add(Jennifer);

        for (int i = 0; i < phoneBook.size(); i++) {
            System.out.println(phoneBook.get(i));
        }
    }
}

问题 - 该程序没有阻止其运行，但是它没有通过循环显示5个对象的内容。

package phonebook;
import java.util.ArrayList;
public class PhoneBookEntry {
public PhoneBookEntry(String personName, int phoneNumber) {
}
public static void main(String[] args) {
ArrayList<PhoneBookEntry> phoneBook = new ArrayList<PhoneBookEntry>();
PhoneBookEntry Jack = new PhoneBookEntry("Jack Daniel", 678-439-5823);
PhoneBookEntry Dave = new PhoneBookEntry("Dave Daniel", 366-263-1363);
PhoneBookEntry John = new PhoneBookEntry("John Daniel", 404-642-8642);
PhoneBookEntry Judy = new PhoneBookEntry("Judy Daniel", 232-952-9142);
PhoneBookEntry Jennifer = new PhoneBookEntry("Jennifer Daniel", 563-124-8246);
for (int i = 0; i < phoneBook.size(); i++) {
System.out.println(phoneBook.get(i));
}
}
}

答案1

得分: 2

你没有将你的对象添加到你的ArrayList中。
使用：phoneBook.add(对象)

public static void main(String[] args) {
    ArrayList<PhoneBookEntry> phoneBook = new ArrayList<PhoneBookEntry>();

    phoneBook.add(new PhoneBookEntry("Jack Daniel", 678-439-5823));
    //等等...
        
    for (int i = 0; i < phoneBook.size(); i++) {
        System.out.println(phoneBook.get(i));
    }
}

public static void main(String[] args) {
    ArrayList<PhoneBookEntry> phoneBook = new ArrayList<PhoneBookEntry>();

    phoneBook.add(new PhoneBookEntry("Jack Daniel", 678-439-5823));
    //etc..
        
    for (int i = 0; i < phoneBook.size(); i++) {
        System.out.println(phoneBook.get(i));
    }
}

答案2

得分: 0

你需要将所有元素添加到 ArrayList 中。为了简化操作，你可以使用 Arrays.asList。

ArrayList<PhoneBookEntry> phoneBook = new ArrayList<PhoneBookEntry>(
   Arrays.asList(new PhoneBookEntry("Jack Daniel", 678-439-5823),
        new PhoneBookEntry("Dave Daniel", 366-263-1363),
        new PhoneBookEntry("John Daniel", 404-642-8642),
        new PhoneBookEntry("Judy Daniel", 232-952-9142),
        new PhoneBookEntry("Jennifer Daniel", 563-124-8246)
   )
);  

如果你想保留变量名：

ArrayList<PhoneBookEntry> phoneBook = new ArrayList<PhoneBookEntry>(
   Arrays.asList(Jack, Dave, John, Judy, Jennifer)
);

ArrayList<PhoneBookEntry> phoneBook = new ArrayList<PhoneBookEntry>(
Arrays.asList(new PhoneBookEntry("Jack Daniel", 678-439-5823),
new PhoneBookEntry("Dave Daniel", 366-263-1363),
new PhoneBookEntry("John Daniel", 404-642-8642),
new PhoneBookEntry("Judy Daniel", 232-952-9142),
new PhoneBookEntry("Jennifer Daniel", 563-124-8246)
)
);  

ArrayList<PhoneBookEntry> phoneBook = new ArrayList<PhoneBookEntry>(
Arrays.asList(Jack, Dave, John, Judy, Jennifer)
);