我在这里把SSCCE扔到了一起：
House.java：
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
public class House {
private Status currentStatus;
private String city;
private Date date;
public enum Status { AVAILABLE,
SOLD,
CONTINGENT
}
public House(Status s, String c, String d) throws ParseException {
currentStatus = s;
city = c;
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
date = sdf.parse(d);
}
}
SortingTest.java：
import java.text.ParseException;
import java.util.HashSet;
import sortingtest.House.Status;
public class SortingTest {
public static void main(String[] args) throws ParseException {
HashSet<House> houses = new HashSet<House>();
houses.add(new House(Status.AVAILABLE, "New York City", "2007-11-11"));
houses.add(new House(Status.SOLD, "Los Angeles", "2005-06-11"));
houses.add(new House(Status.AVAILABLE, "Chicago", "2012-05-03"));
houses.add(new House(Status.CONTINGENT, "Portland", "2007-10-11"));
//Sort HashSet of House objects by criteria listed below
//sort by Status.AVAILABLE
//call sort
//System.out.println("Sorted by available");
//iterate set and print out sorted houses
//sort by Status.SOLD
//call sort
//System.out.println("Sorted by sold");
//iterate set and print out sorted houses
//sort by Status.CONTINGENT
//call sort
//System.out.println("Sorted by contingent");
//iterate set and print out sorted houses
//sort by City
//call sort
//System.out.println("Sorted alphabetically by City");
//iterate set and print out sorted houses
//sort by City
//call sort
//System.out.println("Sorted reverse alphabetically by City");
//iterate set and print out sorted houses
//sort by Date (newest)
//call sort
//System.out.println("Sorted by newest date (fewest days on market)");
//iterate set and print out sorted houses
//sort by Date (oldest)
//call sort
//System.out.println("Sorted oldest date (most days on market)");
//iterate set and print out sorted houses
}
}
所以最终我想要创建一个SetSorter类，我可以调用一个方法来返回以特定格式排序的Set。
如果您不想阅读代码中的注释，我想根据以下内容进行排序：
我已经对它进行了一些阅读，看起来人们建议将其放入TreeSet进行排序和使用比较器。我已经看过多个例子，人们要么为比较器创建一个单独的类，要么使指定的类实现可比较。
我没有看到的是有人写了一个额外的类来处理所有的排序。这可能吗？如果是这样，有人可以告诉我从哪里开始？这些似乎比典型的整数比较稍微复杂一些。
编辑以澄清
按 Status.AVAILABLE 排序时，我希望Set能够按以下方式显示对象：
按 Status.CONTINGENT 排序时，我希望该集按如下方式排序：
按 Status.SOLD 排序时，我希望按以下方式排序：
编辑＃2终极目标：
我想有一个类，我可以简单地调用方法来对集合进行排序。
即：
//sort by date
SetSorter.sortByData(treeSet); //returns TreeSet sorted by date
//sort by city
SetSorter.sortByCity(treeSet); //returns TreeSet sorted by City
//sort by other criteria
编辑＃3
class SortByCity implements Comparator<House> {
@Override
public int compare(House h1, House h2) {
return h1.getCity().compareTo(h1.getCity());
}
}
houses = new TreeSet(new SortByCity());
我认为这是一种简单的方法，但这些都是小班，而且（在我看来）看起来很混乱。谁想在.java中有7个迷你课？
有人可以为我提供一些替代示例吗？
答案 0 :(得分：1)
以下是一些有关排序的示例。我没有执行日期或反向字母排序（这是一项任务）。请注意有关将两个房屋比较为值0的内联评论！
public class HouseSorter {
enum Status {
SOLD, AVAILABLE, CONTINGENT;
}
/**
* Immutable house (if a house is sold or not does not change a house, use a
* Map instead).
*/
private static class House {
private final String city;
House(String city) {
this.city = city;
}
public String getCity() {
return city;
}
@Override
public String toString() {
return "House in " + city;
}
@Override
public boolean equals(Object obj) {
if (obj == null) {
return false;
}
if (!House.class.isAssignableFrom(obj.getClass())) {
return false;
}
return this.city.equalsIgnoreCase(((House) obj).city);
}
@Override
public int hashCode() {
return city.hashCode();
}
}
public static SortedSet<House> sortAlphabetically(Set<House> houses) {
TreeSet<House> sortedHouses = new TreeSet<House>(
new Comparator<House>() {
@Override
public int compare(House o1, House o2) {
return o1.getCity().compareTo(o2.getCity());
}
});
sortedHouses.addAll(houses);
return sortedHouses;
}
public static SortedSet<House> sortByStatus(
final Map<House, Status> houseStatusMap) {
TreeSet<House> sortedHouses = new TreeSet<House>(
new Comparator<House>() {
@Override
public int compare(House o1, House o2) {
int compareByStatus = houseStatusMap.get(o1).compareTo(
houseStatusMap.get(o2));
if (compareByStatus != 0) {
return compareByStatus;
}
// you need an additional compare, until none of the
// houses compare with result 0
// otherwise the houses would be equal and therefore
// removed from the set
return o1.getCity().compareTo(o2.getCity());
}
});
sortedHouses.addAll(houseStatusMap.keySet());
return sortedHouses;
}
/**
* @param args
*/
public static void main(String[] args) {
final Map<House, Status> houseStatusMap = new HashMap<House, Status>();
House house0 = new House("Beverwijk");
houseStatusMap.put(house0, Status.SOLD);
House house1 = new House("Opmeer");
houseStatusMap.put(house1, Status.SOLD);
House house2 = new House("Amstelveen");
houseStatusMap.put(house2, Status.AVAILABLE);
House house3 = new House("Haarlem");
houseStatusMap.put(house3, Status.CONTINGENT);
System.out.println(sortAlphabetically(houseStatusMap.keySet()));
System.out.println(sortByStatus(houseStatusMap));
}
}