嘿我正在尝试在我的主代码中找出一种方法，将类DVD的age属性与该对象的所有其他实例进行比较，以查看哪个属性是最大和最小的。任何人都可以引导我朝着正确的方向前进。如果有帮助，我可以发布主方法和其他类吗？
DVD类：
public class DVD
{
private String id;
private String title;
private String genre;
private int age;
public DVD(String id, String title, String genre, int age)
{
this.id = id;
this.title = title;
this.genre = genre;
this.age = age;
}
public String getId()
{
return id;
}
public String getTitle()
{
return title;
}
public String getGenre()
{
return genre;
}
public int getAge()
{
return age;
}
//Setters
public void setID(String idIn)
{
id = idIn;
}
public void setTitle(String titleIn)
{
title = titleIn;
}
public void setGenre(String genreIn)
{
genre = genreIn;
}
public void setAge(int ageIn)
{
age = ageIn;
}
public String toString()
{
//Building string here
String x = "The id is: "+id+
"\nThe title is: "+title+
"\nThe genre is: "+genre+
"\nThe age is: "+age;
return x;
}
}//end of class
DVDShop课程：
public class DVDShop
{
//attributes (instance variables)
private DVD[] dvdList;
private int total;
//Constructors
public DVDShop (int maxNum)
{
dvdList = new DVD[maxNum];
total=0;
}
//accessor
public int getTotal()
{
return total;
}
// check if the list is full
public boolean isFull()
{
if (total == dvdList.length)
{
return true; // list is full
}
else
{
return false; // list is empty
}
}
// check if the list is empty
public boolean isEmpty()
{
if (total == 0)
{
return true; // list is empty
}
else
{
return false; // list is not empty
}
}
// add an item to the array
public boolean add(DVD DVDIn)
{
if (!isFull()) // check if list is full
{
dvdList[total] = DVDIn; // add item
total++; // increment total
return true; // indicate success
}
else
{
return false; // indicate failure
}
}
// helper method to find the id of a specified account
public int search(String dvdNumIn)
{
for(int i = 0; i < total; i++)
{
DVD tempDVD = dvdList[i]; // find the account at index i
String tempNumber = tempDVD.getId(); // get dvd number
if(tempNumber.equals(dvdNumIn))
{
return i;
}
}
return -999;
}
public boolean delete(String numberIn)
{
int index;
index = search(numberIn); // call the search method first
// if it could find the DVD it will return the element in the array that it is stored
// if not it will return a dummy value of -999
if(index == -999)
{
return false; // remove was unsuccessful
}
else
{
for(int i = index; i<= total-2; i++)
{
dvdList[i] = dvdList[i+1];
}
total--; // decrement total number of DVDs
return true; // remove was successful
}
}
public DVD getItem(String numIn)
{
int index;
index = search(numIn);
if(index == -999)
{
return null; // indicate invalid index
}
else
{
return dvdList[index];
}
}
}
主要方法：
public class Question1
{
public static void main (String args[])
{
//creation of instance of DVDs called myDVDshop size 10
DVDShop myDVDshop = new DVDShop(10);
int choice;
int i;
//start of do while() loop for repetition
do{
System.out.println();
System.out.println("Shop System");
System.out.println("1. Add DVD");
System.out.println("2. Search for DVD");
System.out.println("3. Show number of DVDs in shop");
System.out.println("4. Delete a DVD");
System.out.println("5. Show Details of a DVD");
System.out.println("6. Exit System");
System.out.print("Please enter your choice: ");
choice = EasyScanner.nextInt();
System.out.println();
//Start of switch()
switch(choice)
{
case 1:
addDVD(myDVDshop);
break;
case 2:
searchDVD(myDVDshop);
break;
case 3:
Stock(myDVDshop);
break;
case 4:
deleteDVD(myDVDshop);
break;
case 5:
showDetails(myDVDshop);
break;
case 6:
System.out.println("Goodbye...");
break;
default:
System.out.println("Invalid entry, please reenter valid selection");
}//end of switch()
}while(choice!=6);
}//end of class
//start of methods
private static void showDetails(DVDShop myDVDshop)
{
String number;
// get details from user
System.out.print("Enter Id of DVD: ");
number = EasyScanner.nextString();
DVD theDVD = myDVDshop.getItem(number);
if (theDVD == null)
{
System.out.println();
System.out.println("No such DVD exists");
}
else
{
System.out.println();
System.out.println("DVD Id: " + theDVD.getId());
System.out.println("DVD title: " + theDVD.getTitle());
System.out.println("DVD genre: " + theDVD.getGenre());
System.out.println("DVD age category: " + theDVD.getAge());
System.out.println();
}
}
private static void deleteDVD(DVDShop myDVDshop)
{
String id;
boolean toDelete;
System.out.print("Please enter the id number of the DVD you would like to delete: ");
id = EasyScanner.nextString();
System.out.println();
toDelete = myDVDshop.delete(id);
if (toDelete == true)
{
System.out.println("The DVD has been deleted from the system");
}
else
{
System.out.println("The DVD could not be deleted from the system");
}
System.out.println();
}
private static void addDVD(DVDShop myDVDshop)
{
String id, title, genre;
int age;
boolean ok;
// DVDs myDVDshop = new DVDs(10);
// Entering required data
System.out.print("Enter id number: ");
id = EasyScanner.nextString();
System.out.print("Enter title of DVD: ");
title = EasyScanner.nextString();
System.out.print("Enter genre of DVD: ");
genre = EasyScanner.nextString();
System.out.print("Enter age category of DVD: ");
age = EasyScanner.nextInt();
System.out.println();
DVD DVD1 = new DVD(id,title,genre,age);
ok = myDVDshop.add(DVD1);
if (ok == false)
{
System.out.println("The list is full");
}
else
{
System.out.println("DVD added");
}
System.out.println();
}
private static void searchDVD(DVDShop myDVDshop)
{
//Requesting value from the user to search for.
System.out.print("Which DVD id do you want to search for: ");
String idIn=EasyScanner.nextString();
System.out.println();
int search1 = myDVDshop.search(idIn);
if(search1 == -999)
{
System.out.println("DVD not in the system");
}
else
{
System.out.println("The DVD is in the system at position number "+search1+ " in the array.");
}
System.out.println();
}
private static void Stock(DVDShop myDVDshop)
{
System.out.println("Total stock is: "+myDVDshop.getTotal());
}
}//end of class
答案 0 :(得分：2)
在Comparable<T>类上实现DVD接口，如下所示：
public class DVD implements Comparable<DVD>
这需要您定义一个新方法; compareTo
这允许您定义两个对象相对于彼此的排序方式。在这种情况下，对于较旧的DVD来说，更大的＆＃34;更有意义。比较新的DVD，所以compareTo的（非常基本的）实现看起来像这样：
public int compareTo(DVD that) {
if (age > that.getAge()) {
// this is older than that
return 1;
} else if (age < that.getAge()) {
// this is newer than that
return -1;
}
// this is the same age as that
return 0;
}
完成后，您可以使用Arrays.sort(dvdList)将您的收藏分类为年龄顺序。从那里开始，需要选择集合中的第一个和最后一个元素，这些元素将分别是您最早和最新的DVD。
在实践中，您可能希望为compareTo添加一些空值检查，以避免在that为null时出现问题。
答案 1 :(得分：0)
Can any one steer me in the right direction.
添加查找最大和最小的东西的方法到DVDShop类如下。
public class DVDShop
{
private DVD[] dvdList;
---snip---
public int largestAge()
{
//find and return largest age from dvdList.
}
public int smallestAge()
{
//find and return smallest age from dvdList.
}
}