Java 使用Stream()过滤(filter)筛选List<T>列表数据并记录过滤的值日志方法代码

示例代码：

List<Person> persons = Arrays.asList(new Person("John"), new Person("Paul"));

1､使用filter()进行过滤筛选数据

List<Person> filtered = persons.stream()
      .filter(p -> {
          if (!"John".equals(p.getName())) {
              return true;
          } else {
              System.out.println(p.getName());
              return false;
          }})
      .collect(Collectors.toList());

或

//使用包装器
private static <T> Predicate<T> andLogFilteredOutValues(Predicate<T> predicate) {
    return value -> {
        if (predicate.test(value)) {
            return true;
        } else {
            System.out.println(value);
            return false;
        }
    };
}
List<Person> persons = Arrays.asList(new Person("John"), new Person("Paul"));
List<Person> filtered = persons.stream()
  .filter(andLogFilteredOutValues(p -> !"John".equals(p.getName())))
  .collect(Collectors.toList());

2､collect()和Collectors.partitioningBy()进行过滤筛选数据

Map<Boolean,List<Person>> map = persons.stream()
    .collect(Collectors.partitioningBy(p -> "John".equals(p.getName())));
System.out.println("filtered: " + map.get(true));
List<Person> result = map.get(false);

或

List<Person> result = persons.stream()
    .collect(Collectors.collectingAndThen(
        Collectors.partitioningBy(p -> "John".equals(p.getName())),
        map -> {
            System.out.println("filtered: " + map.get(true));
            return map.get(false);
        }));