我以前曾使用此站点来帮助我完成许多编程任务,但找不到与我现在遇到的问题类似的东西。
我试图首先使用方法myHobbies
在person类的toString中打印printHobby
数组,并计算用户在printDuration
中进行Hobby的总时间。我不确定为什么我不能使它正常工作并且一直在挣扎一段时间。
任何帮助,将不胜感激。这是我的课。这是我第一次发布,因此如果我做错了什么,请告诉我。
//--------------------Person--------------------
public class Person {
String fName;
String lName;
String address;
int age;
String hobbyText;
private double durationH = 0;
private double totalDuration = 0;
Person(String f, String l, String a, int ag) {
fName = f;
lName = l;
address = a;
age = ag;
}
static Hobby[] myHobbies = new Hobby[5];
static int i = 0;
public static void setHobby(Hobby mh) {
myHobbies[i] = mh;
i++;
}
public String toString() {
return fName + " " + lName + " " + address + " " + age + " "
+ printDuration() + " ";
}
public double printDuration() {
for (int k = 0; k < myHobbies.length; k++)
totalDuration += myHobbies[k].getDuration();
return totalDuration;
}
public String printHobbies() {
for (int j = 0; j < myHobbies.length; j++)
hobbyText = myHobbies[j].toString();
return hobbyText;
}
}
//--------------------HobbyDriver--------------------
import java.util.Scanner;
public class HobbyDriver {
public static void main(String[] args) {
Hobby[] newHobby = {
new Hobby("Comics", "09/25/2012", "The Comic Store", 1),
new Hobby("Baseball", "09/30/2012", "Fenway Park", 3),
new Hobby("Programming", "09/212/2012", "Home", 6),
new Hobby("Board Games", "09/01/2012", "Tom's House", 3),
new Hobby("Watching Dr. Who", "09/27/2012", "Home", 1) };
String personChoice;
Scanner hobbyScan = new Scanner(System.in);
do {
String fName;
String lName;
int age;
String address;
String hobbyName;
String partDate;
String location;
double duration;
int userHobby;
String hobbyChoice;
System.out.println("What is your first name?");
fName = hobbyScan.nextLine();
System.out.println("What is your last name?");
lName = hobbyScan.nextLine();
System.out.println("What is your address?");
address = hobbyScan.nextLine();
System.out.println("What is your age?");
age = hobbyScan.nextInt();
hobbyScan.nextLine();
do {
System.out
.println("What hobbies would you like to do?\n"
+ "choose between Comics(0)\nBaseball(1)\nProgramming(2)\nBoard Games(3)\nWatching Dr.Who(4)\n"
+ "\nEnter the name of the hobby and then press enter");
userHobby = hobbyScan.nextInt();
hobbyScan.nextLine();
System.out
.println("Would you like to add another hobby? (enter yes/no)");
hobbyChoice = hobbyScan.nextLine();
Person.setHobby(newHobby[userHobby]);
} while (hobbyChoice.equals("yes"));
System.out
.println("Would you like to add another person? (enter yes/no)");
personChoice = hobbyScan.nextLine();
int i = 0;
Person[] newPerson = new Person[5];
newPerson[i] = new Person(fName, lName, address, age);
System.out.println(newPerson[i].toString());
i++;
} while (personChoice.equals("yes"));
}
}
//--------------------Hobby--------------------
public class Hobby {
private String hobbyName;
private String partDate;
private String location;
private double duration;
Hobby(String h, String p, String l, double d) {
hobbyName = h;
partDate = p;
location = l;
duration = d;
}
public String toString() {
return hobbyName + " " + partDate + " " + location + " " + duration;
}
public void setDuration(double d) {
d = duration;
}
public double getDuration() {
return duration;
}
}
最佳答案
问题如下:
public String printHobbies() {
for (int j = 0; j < myHobbies.length; j++)
hobbyText = myHobbies[j].toString();
return hobbyText;
}
首先,在每个循环中覆盖字符串。写
hobbyText += myHobbies[j].toString();
其次,如果不添加5个爱好,您将获得NPE,因为数组中的每个项目开头都是空。
因此,您将必须检查myHobbies [j]是否不为空:
public String printHobbies() {
for (int j = 0; j < myHobbies.length; j++) {
if(myHobbies[j] != null) {
hobbyText += myHobbies[j].toString();
}
}
return hobbyText;
}
您可能还需要看一下Collections:http://docs.oracle.com/javase/1.4.2/docs/api/java/util/Collections.html