应用 OR 谓词 Java 8

Question

我有员工对象

public class Employee {

    public Employee(Integer id, Integer age, String gender, String fName, String lName) {
        this.id = id;
        this.age = age;
        this.gender = gender;
        this.firstName = fName;
        this.lastName = lName;
    }

    private Integer id;
    private Integer age;
    private String gender;
    private String firstName;
    private String lastName;

我有两个谓词

public static Predicate<Employee> firstNameLike(final String name) {
        return p -> p.getFirstName().contains(name);
    }


    public static Predicate<Employee> isAdultFemale() {
        return p -> p.getAge() > 18 && p.getGender().equalsIgnoreCase("F");
    }

我正在对员工应用多个过滤器，例如

public class TestEmployeePredicates {
    public static void main(String[] args) {

        Employee e2 = new Employee(2, 13, "F", "Martina", "Hengis");
        Employee e5 = new Employee(5, 19, "F", "Cristine", "Maria");
        Employee e7 = new Employee(7, 68, "F", "Melissa", "Roy");
        Employee e9 = new Employee(9, 15, "F", "Neetu", "Singh");


        Employee e1 = new Employee(1, 23, "M", "Rick", "Beethovan");
        Employee e3 = new Employee(3, 43, "M", "Ricky", "Martin");
        Employee e4 = new Employee(4, 26, "M", "Jon", "Lowman");
        Employee e6 = new Employee(6, 15, "M", "David", "Feezor");
        Employee e8 = new Employee(8, 79, "M", "Alex", "Gussin");
        Employee e10 = new Employee(10, 45, "M", "Naveen", "Jain");


        List<Employee> employees = new ArrayList<Employee>();
        employees.addAll(Arrays.asList(new Employee[]{e1, e2, e3, e4, e5, e6, e7, e8, e9, e10}));


        List<Predicate<Employee>> predicates = new ArrayList<>();


        predicates.add(EmployeePredicates.isAdultFemale());
        predicates.add(EmployeePredicates.firstNameLike("J"));


        final Predicate<Employee> employeePredicate = predicates.stream().reduce(Predicate::and).get();

        //OR adult male
        employeePredicate.or(EmployeePredicates.isAdultMale());


        final List<Employee> collect = employees.stream().filter(employeePredicate).collect(Collectors.toList());

        System.out.println(collect.size());

按照我的逻辑，它应该检查列表

如果它的 AdultFemale 和 firstname like "J" 或者它的 Adult Male

但这并不符合逻辑。我在这里做错了什么？即使员工是 Adult MALE，它也会被过滤掉。

Answer 1

or 不会改变它所使用的 Predicate 对象，它 returns a Predicate 具有该逻辑.在这里，由于您没有在任何地方分配 return 值，您只是丢失了它，并且 or 调用什么也不做。相反，您应该将其保存到一个变量中。例如：

final Predicate<Employee> employeePredicate = 
    predicates.stream().reduce(Predicate::and).get();

// OR adult male
// Note that the result is saved back to employeePredicate
employeePredicate = employeePredicate.or(EmployeePredicates.isAdultMale());

应用 OR 谓词 Java 8

Applying OR predicate Java 8

java

predicate

filter

java-8