本文目录导读：
我来介绍几种Java集合筛选的常用实现方法：
传统for循环筛选
import java.util.ArrayList;
import java.util.List;
public class TraditionalFilter {
public static void main(String[] args) {
List<Integer> numbers = new ArrayList<>();
for (int i = 1; i <= 10; i++) {
numbers.add(i);
}
// 筛选大于5的数
List<Integer> filtered = new ArrayList<>();
for (Integer num : numbers) {
if (num > 5) {
filtered.add(num);
}
}
System.out.println("大于5的数: " + filtered);
}
}
Java 8 Stream API筛选
import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;
public class StreamFilter {
public static void main(String[] args) {
List<String> names = Arrays.asList("Alice", "Bob", "Charlie", "David", "Eve");
// 筛选长度大于3的名字
List<String> filtered = names.stream()
.filter(name -> name.length() > 3)
.collect(Collectors.toList());
System.out.println("长度大于3的名字: " + filtered);
// 链式筛选：长度大于3且包含字母a
List<String> complexFilter = names.stream()
.filter(name -> name.length() > 3)
.filter(name -> name.contains("a") || name.contains("A"))
.collect(Collectors.toList());
System.out.println("复杂筛选结果: " + complexFilter);
}
}
对象筛选案例
import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;
class Person {
private String name;
private int age;
private String city;
public Person(String name, int age, String city) {
this.name = name;
this.age = age;
this.city = city;
}
// getters
public String getName() { return name; }
public int getAge() { return age; }
public String getCity() { return city; }
@Override
public String toString() {
return name + "(" + age + "岁," + city + ")";
}
}
public class ObjectFilter {
public static void main(String[] args) {
List<Person> people = new ArrayList<>();
people.add(new Person("张三", 25, "北京"));
people.add(new Person("李四", 30, "上海"));
people.add(new Person("王五", 20, "北京"));
people.add(new Person("赵六", 35, "广州"));
people.add(new Person("孙七", 28, "上海"));
// 筛选出所有年龄大于25岁的人
List<Person> adults = people.stream()
.filter(p -> p.getAge() > 25)
.collect(Collectors.toList());
System.out.println("年龄大于25岁: " + adults);
// 筛选出所有北京的人
List<Person> beijingPeople = people.stream()
.filter(p -> "北京".equals(p.getCity()))
.collect(Collectors.toList());
System.out.println("北京人: " + beijingPeople);
// 多条件筛选：北京且年龄大于22岁
List<Person> complexFilter = people.stream()
.filter(p -> "北京".equals(p.getCity()) && p.getAge() > 22)
.collect(Collectors.toList());
System.out.println("北京且年龄>22: " + complexFilter);
}
}
使用CollectionUtils工具类
import org.apache.commons.collections4.CollectionUtils;
import org.apache.commons.collections4.Predicate;
import java.util.ArrayList;
import java.util.List;
public class CollectionUtilsFilter {
public static void main(String[] args) {
List<Integer> numbers = new ArrayList<>();
for (int i = 1; i <= 10; i++) {
numbers.add(i);
}
// 使用Predicate筛选偶数
List<Integer> evens = new ArrayList<>(CollectionUtils.select(
numbers,
new Predicate<Integer>() {
@Override
public boolean evaluate(Integer n) {
return n % 2 == 0;
}
}
));
System.out.println("偶数: " + evens);
// 筛选大于5的数
List<Integer> greaterThan5 = new ArrayList<>(CollectionUtils.select(
numbers,
n -> n > 5
));
System.out.println("大于5: " + greaterThan5);
}
}
使用Google Guava
import com.google.common.base.Predicate;
import com.google.common.collect.Collections2;
import com.google.common.collect.Lists;
import java.util.Collection;
import java.util.List;
public class GuavaFilter {
public static void main(String[] args) {
List<String> cities = Lists.newArrayList("北京", "上海", "广州", "深圳", "杭州");
// 筛选包含"京"的城市
Collection<String> filtered = Collections2.filter(cities,
new Predicate<String>() {
@Override
public boolean apply(String city) {
return city.contains("京");
}
}
);
System.out.println("包含'京'的城市: " + filtered);
// Java 8 lambda表达式
Collection<String> filtered2 = Collections2.filter(cities,
city -> city.length() > 2
);
System.out.println("名称长度>2的城市: " + filtered2);
}
}
性能优化：并行流筛选
import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;
public class ParallelStreamFilter {
public static void main(String[] args) {
List<Integer> numbers = new ArrayList<>();
for (int i = 1; i <= 1000000; i++) {
numbers.add(i);
}
// 使用并行流提高大数据量筛选性能
List<Integer> filtered = numbers.parallelStream()
.filter(n -> n > 500000)
.filter(n -> n % 2 == 0)
.collect(Collectors.toList());
System.out.println("筛选结果数量: " + filtered.size());
}
}
自定义筛选方法
import java.util.ArrayList;
import java.util.List;
import java.util.function.Predicate;
public class GenericFilter {
// 通用的筛选方法
public static <T> List<T> filter(List<T> list, Predicate<T> predicate) {
List<T> result = new ArrayList<>();
for (T item : list) {
if (predicate.test(item)) {
result.add(item);
}
}
return result;
}
public static void main(String[] args) {
List<Integer> numbers = new ArrayList<>();
for (int i = 1; i <= 10; i++) {
numbers.add(i);
}
// 使用自定义筛选方法
List<Integer> evens = filter(numbers, n -> n % 2 == 0);
System.out.println("偶数: " + evens);
List<Integer> odds = filter(numbers, n -> n % 2 != 0);
System.out.println("奇数: " + odds);
}
}
推荐使用：对于Java 8及以上版本，Stream API是最简洁、最灵活的筛选方式，它支持链式操作、并行处理，代码可读性强。
