聚合操作例子(oracle甲骨文官网示例)
import java.lang.Iterable;import java.lang.Number;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.function.BinaryOperator;
import java.util.function.Consumer;
import java.util.function.Function;
import java.util.function.Predicate;
public class BulkDataOperationsExamples {
public static void main(String... args) {
// Create sample data
List<Person> roster = Person.createRoster();
// 1. Print names of members, for-each loop
System.out.println("Members of the collection (for-each loop):");
for (Person p : roster) {
System.out.println(p.getName());
}
// 2. Print names of members, forEach operation
System.out.println("Members of the collection (bulk data operations):");
roster
.stream()
.forEach(e -> System.out.println(e.getName()));
// 3. Print names of male members, forEach operation
System.out.println(
"Male members of the collection (bulk data operations):");
roster
.stream()
.filter(e -> e.getGender() == Person.Sex.MALE)
.forEach(e -> System.out.println(e.getName()));
// 4. Print names of male members, for-each loop
System.out.println("Male members of the collection (for-each loop):");
for (Person p : roster) {
if (p.getGender() == Person.Sex.MALE) {
System.out.println(p.getName());
}
}
// 5. Get average age of male members of the collection:
double average = roster
.stream()
.filter(p -> p.getGender() == Person.Sex.MALE)
.mapToInt(Person::getAge)
.average()
.getAsDouble();
System.out.println(
"Average age of male members (bulk data operations): " +
average);
}
}
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