使用构造函数名称的变量创建一个小型数据库
使用构造函数名称的变量创建一个小型数据库
提问于 2014-01-10 10:42:05
我正在尝试创建一个应用程序，它可以让您
1-将人员添加到小型数据库
2-将它们的名称附加到数组中
3-检索之前输入的信息时，该数组将用于选择人员
4-检索所选人员的唯一信息
我有两个类，Person()和PeopleManager()，person ()用给定的变量构造一个新的person，并存储该信息供以后读取。
Person类：
public class Person extends Object
{
private static int theNumPersons = 0; // initialize num
private String itsFirstName;
private String itsLastName;
private int itsBirthYear;
public Person (String first, String last, int year)
{
super();
theNumPersons++; // update num
itsFirstName = first;
itsLastName = last; // initialize last name
itsBirthYear = year;
}
/** Tell how many different Persons exist. */
public static int getNumPersons() // access num
{
return theNumPersons;
}
/** Return the birth year. */
public int getBirthYear()
{
return itsBirthYear;
}
/** Return the first name. */
public String getFirstName()
{
return itsFirstName;
}
/** Return the last name. */
public String getLastName() // access last name
{
return itsLastName;
}
/** Replace the last name by the specified value. */
public void setLastName (String name) // update last name
{
itsLastName = name;
}
}PeopleManager类：
import java.util.*;
import javax.swing.*;
public class PeopleManager
{
static ArrayList names = new ArrayList();
static int selection;
public static void main()
{
askSelection();
}
public static void askSelection()
{
Object[] options = { "Add to Database", "Retrieve Info" };
selection = JOptionPane.showOptionDialog(null, "What would you like to do?", "People Database Application", JOptionPane.DEFAULT_OPTION, JOptionPane.QUESTION_MESSAGE, null, options, options[0]);
executeSelection();
}
public static void executeSelection()
{
if (selection == 0)
{
addPerson();
askSelection();
}
if (selection == 1)
{
Object[] nameArray = names.toArray();
Object person = JOptionPane.showInputDialog(null, "Select person to grab info from.", "People Database Application", JOptionPane.DEFAULT_OPTION, null, nameArray, nameArray[0]);
getInfo(person);
askSelection();
}
}
public static void addPerson()
{
String newFirst = JOptionPane.showInputDialog (null, "Enter the first name.", "John");
String newLast = JOptionPane.showInputDialog (null, "Enter the last name.", "Doe");
String sNewYear = JOptionPane.showInputDialog (null, "Enter that person's birth year.", "1965");
String newFullName = (newFirst + " " + newLast);
int iNewYear = Integer.parseInt(sNewYear);
names.add(newFullName);
Person newFullName = new Person (newFirst, newLast, iNewYear);
JOptionPane.showMessageDialog (null, "Person successfully added.");
}
public static void getInfo(Object p)
{
String infoFirst = p.getFirstName;
String infoLast = p.getLastName;
String infoYear = p.getBirthYear;
String databaseSize = getNumPersons();
JOptionPane.showMessageDialog(null, "First Name: " + infoFirst + "\nLast Name: " + infoLast + "\nBirth Year: " + infoYear + "\n\nTotal people in database: " + databaseSize);
}
}我知道我做得不对，而且我非常确定这与我试图通过使用变量创建一个新的Person()的方式有关。问题是，如果我不能使用一个变量来创建一个新的Person()，我怎么能给应用程序用户提供特定于他们输入的人的统计数据呢？
Stack Overflow用户
发布于 2014-01-10 10:48:03
您正在创建一个新的Person对象
names.add(newFullName);
Person newFullName = new Person (newFirst, newLast, iNewYear);但是您并没有保留该引用(通过添加数组或其他方法)，而是拥有跟踪名称的names数组。此外，您应该将变量重命名为其他名称，因为您有2个变量的名称相同。
编辑:正如你所问的，这里有一个简单的例子。
class1：
public class Person
{
public String name;
public String lastname;
public Person(String name, String lastname)
{
this.name = name;
this.lastname = lastname;
}
public String toString()
{
return this.name + " " + this.lastname;
}
}第二类：
import java.util.*;
public class PersonManager{
//array list to keep track of all the Person objects that will be created
public static ArrayList<Person>peoples = new ArrayList<Person>();
//assume this function takes input from user and returns a new
//person object
public static Person getPerson(String name, String last)
{
Person p = new Person(name, last);
return p;
}
//this function removes a person with the first name
public static boolean removePerson(String name)
{
//we should loop through the array and find the object we want to delete
Person objectToRemove = null;
for (Person p : peoples)
{
if (p.name.equals(name))
{
//this is the object we want to remove
//because the name matched
objectToRemove = p;
break;
}
}
//we will actually remove the object outside of the loop
//so we don't run into errors...
if (objectToRemove != null)
{
//tell array list to remove the object we wanted to delete
peoples.remove(objectToRemove);
System.out.println("\nRemoving person = "+objectToRemove);
}
return objectToRemove != null;
}
public static void printInfo()
{
System.out.println("\n\nPrinting info");
//loop through all the object in the peoples array and print out their names
for (Person p : peoples)
{
System.out.println(p);
}
System.out.println("In total, there are "+ peoples.size() +" objects saved in the array");
}
public static void main(String []args)
{
//creating 3 different people and adding them to the array list
peoples.add(getPerson("John", "Doe"));
peoples.add(getPerson("Jane", "Doe"));
peoples.add(getPerson("Will", "Smith"));
//print all the users in the array and the size of the array
printInfo();
//remove the person with first name = John.
removePerson("John");
//print all the users in the array and the size of the array
printInfo();
}
}页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/21035295
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