如果你想同時基於區與Java 8
Streams位置值則價值distinct
行,它就是這麼簡單:
int countSimilar = (int) searchListList.stream().distinct().count();
或者,如果行的清晰度取決於區域唯一的價值:
int countSimilarByArea = searchListList
.stream()
.collect(
Collectors.toCollection(() -> new TreeSet<SearchList>((
p1, p2) -> p1.getArea().compareTo(p2.getArea()))))
.size();
或者,如果行的清晰度取決於位置唯一的價值:
int countSimilarByLocation = searchListList
.stream()
.collect(
Collectors.toCollection(() -> new TreeSet<SearchList>((
p1, p2) -> p1.getLocation().compareTo(
p2.getLocation())))).size();
用法:
import java.util.ArrayList;
import java.util.List;
import java.util.TreeSet;
import java.util.stream.Collectors;
final class SearchList {
private final String area;
private final String location;
public SearchList(String area, String location) {
this.area = area;
this.location = location;
}
public String getArea() {
return area;
}
@Override
public String toString() {
return "SearchList [area=" + area + ", location=" + location + "]";
}
public String getLocation() {
return location;
}
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + ((area == null) ? 0 : area.hashCode());
result = prime * result
+ ((location == null) ? 0 : location.hashCode());
return result;
}
@Override
public boolean equals(Object obj) {
if (this == obj)
return true;
if (obj == null)
return false;
if (getClass() != obj.getClass())
return false;
SearchList other = (SearchList) obj;
if (area == null) {
if (other.area != null)
return false;
} else if (!area.equals(other.area))
return false;
if (location == null) {
if (other.location != null)
return false;
} else if (!location.equals(other.location))
return false;
return true;
}
}
public class CountSimilar {
public static void main(String[] args) {
List<SearchList> searchListList = new ArrayList<>();
searchListList.add(new SearchList("A", "India"));
searchListList.add(new SearchList("B", "India"));
searchListList.add(new SearchList("A", "India"));
searchListList.add(new SearchList("A", "USA"));
searchListList.add(new SearchList("A", "USA"));
int countSimilar = (int) searchListList.stream().distinct().count();
System.out.println(countSimilar);
int countSimilarByArea = searchListList
.stream()
.collect(
Collectors.toCollection(() -> new TreeSet<SearchList>((
p1, p2) -> p1.getArea().compareTo(p2.getArea()))))
.size();
System.out.println(countSimilarByArea);
int countSimilarByLocation = searchListList
.stream()
.collect(
Collectors.toCollection(() -> new TreeSet<SearchList>((
p1, p2) -> p1.getLocation().compareTo(
p2.getLocation())))).size();
System.out.println(countSimilarByLocation);
}
}
我能看到的主要問題是您要添加的同一個實例'SearchList'到'list1'多次(你應該每次添加一個新的實例)。 ''不執行'是什麼意思? –
你的SearchList有hashCode並且等於overriden? –
你會得到什麼錯誤? – markus