我的代码说我没有 Main 方法，但我不确定为什么或在哪里实现一个？

Question

每当我尝试编译我的代码时，我都会收到一条错误消息，提示我没有 main 方法。我不确定我需要把它放在哪里或如何放。

import java.util.ArrayList;
import java.util.Scanner;
import java.io.*;
// Abstract Base class for Contacts
abstract class Contact {
private static int contactCount = 0;
private int contactID;
private String firstName;
private String lastName;
private String email;
private String phone;
private String contactType;

public Contact(String firstName, String lastName, String email, String phone, String contactType) {
    this.contactID = ++contactCount;
    this.firstName = firstName;
    this.lastName = lastName;
    this.email = email;
    this.phone = phone;
    this.contactType = contactType;
}

public int getContactID() {
    return contactID;
}

public String getFirstName() {
    return firstName;
}

public String getLastName() {
    return lastName;
}

public String getEmail() {
    return email;
}

public String getPhone() {
    return phone;
}

public String getContactType() {
    return contactType;
}

public void setFirstName(String firstName) {
    this.firstName = firstName;
}

public void setLastName(String lastName) {
    this.lastName = lastName;
}

public void setEmail(String email) {
    this.email = email;
}

public void setPhone(String phone) {
    this.phone = phone;
}

public void setContactType(String contactType) {
    this.contactType = contactType;
}

@Override
public String toString() {
    return "Contact{" +
            "contactID=" + contactID +
            ", firstName='" + firstName + '\'' +
            ", lastName='" + lastName + '\'' +
            ", email='" + email + '\'' +
            ", phone='" + phone + '\'' +
            ", contactType='" + contactType + '\'' +
            '}';
}
}
// Sub-class for Personal Contact
class PersonalContact extends Contact {
private String relationship;
private int age;
private String gender;
public PersonalContact(String firstName, String lastName, String email, String phone, String relationship, int age, String gender) {
    super(firstName, lastName, email, phone, "Personal");
    this.relationship = relationship;
    this.age = age;
    this.gender = gender;
}

public String getRelationship() {
    return relationship;
}

public int getAge() {
    return age;
}

public String getGender() {
    return gender;
}

public void setRelationship(String relationship) {
    this.relationship = relationship;
}

public void setAge(int age) {
    this.age = age;
}

public void setGender(String gender) {
    this.gender = gender;
}

@Override
public String toString() {
    return "PersonalContact{" +
            "relationship='" + relationship + '\'' +
            ", age=" + age +
            ", gender='" + gender + '\'' +
            "} " + super.toString();
}
}
// Sub-class for Family Contact
class FamilyContact extends PersonalContact {
private String relation;
public FamilyContact(String firstName, String lastName, String email, String phone, String relationship, int age, String gender, String relation) {
    super(firstName, lastName, email, phone, relationship, age, gender);
    this.relation = relation;
    super.setContactType("Family");
}

public String getRelation() {
    return relation;
}

public void setRelation(String relation) {
    this.relation = relation;
}

@Override
public String toString() {
    return "FamilyContact{" +"relation='" + relation + '\'';
}
}

我真的不明白为什么会出现错误，因为我认为不需要调用 main 方法。我尝试更改/添加一个主要方法，但我只会收到更多错误。任何帮助将不胜感激！

Answer 1

当我尝试做这样的事情时，我收到一条错误消息说

Error: Main method not found in the file, please define the main method as: public static void main(String[] args)

你确定 Java 不需要 main 方法还是我忘记了一些关于 Java 的东西。已经有一段时间了，如果没有，请告诉我。