在Java中,我們可以使用Collectors類來創(chuàng)建自定義的收集器實(shí)現(xiàn)方法。以下是一個(gè)示例,展示了如何創(chuàng)建一個(gè)自定義的收集器,用于計(jì)算一組數(shù)字的平均值:
import java.util.List;
import java.util.stream.Collector;
import java.util.stream.Collectors;
public class CustomCollector {
public static void main(String[] args) {
List<Integer> numbers = List.of(1, 2, 3, 4, 5);
double average = numbers.stream()
.collect(averageCollector());
System.out.println("Average: " + average);
}
public static Collector<Integer, AverageAccumulator, Double> averageCollector() {
return Collector.of(
AverageAccumulator::new,
AverageAccumulator::accumulate,
AverageAccumulator::combine,
AverageAccumulator::getAverage
);
}
static class AverageAccumulator {
private int sum;
private int count;
public AverageAccumulator() {
this.sum = 0;
this.count = 0;
}
public void accumulate(int number) {
sum += number;
count++;
}
public AverageAccumulator combine(AverageAccumulator other) {
this.sum += other.sum;
this.count += other.count;
return this;
}
public double getAverage() {
if (count == 0) {
return 0;
}
return (double) sum / count;
}
}
}
在這個(gè)示例中,我們創(chuàng)建了一個(gè)名為averageCollector
的自定義收集器方法,該方法返回一個(gè)Collector對(duì)象,該對(duì)象將使用AverageAccumulator
來計(jì)算一組數(shù)字的平均值。AverageAccumulator
類用于跟蹤累加的總和和數(shù)量,并提供計(jì)算平均值的方法。最后,我們將這個(gè)自定義的收集器應(yīng)用到一個(gè)整數(shù)列表上,以計(jì)算其平均值并輸出結(jié)果。