JAVA Stream Filter 使用

14 min read

1.定义一个实体体

public class Customer {
    private String name;
    private int points;
    //Constructor and standard getters
}

2.创建一个实体类集合

Customer john = new Customer("John P.", 15);
Customer sarah = new Customer("Sarah M.", 200);
Customer charles = new Customer("Charles B.", 150);
Customer mary = new Customer("Mary T.", 1);

List<Customer> customers = Arrays.asList(john, sarah, charles, mary);

3. 数据筛选

List<Customer> customersWithMoreThan100Points = customers
  .stream()
  .filter(c -> c.getPoints() > 100)
  .collect(Collectors.toList());

附录

  • Arrays.asList 源码

public static <T> List<T> asList(T... a) {
    return new ArrayList<>(a);
}

  • Stream collect 转换stream对象为指定的类型

public static <T>
    Collector<T, ?, List<T>> toList() {
        return new CollectorImpl<>((Supplier<List<T>>) ArrayList::new, List::add,
                                   (left, right) -> { left.addAll(right); return left; },
                                   CH_ID);
    }