应用OR谓词Java 8

内容导读

互联网集市收集整理的这篇技术教程文章主要介绍了应用OR谓词Java 8，小编现在分享给大家，供广大互联网技能从业者学习和参考。文章包含2432字，纯文字阅读大概需要4分钟。

内容图文

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");
    }

我正在向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());

根据我的逻辑,它应该检查列表

如果它的AdultFemale和名字像“J”或其成年男性

但这不符合逻辑.我在这做错了什么？即使员工是成人MALE,也会将其过滤掉.

解决方法:

or不会改变它所使用的Predicate对象,它会返回带有该逻辑的Predicate.在这里,既然您没有在任何丢失它的地方分配返回值,那么或者呼叫什么都不做.相反,您应该将其保存到变量中.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());

内容总结

以上是互联网集市为您收集整理的应用OR谓词Java 8全部内容，希望文章能够帮你解决应用OR谓词Java 8所遇到的程序开发问题。 如果觉得互联网集市技术教程内容还不错，欢迎将互联网集市网站推荐给程序员好友。

内容备注

版权声明：本文内容由互联网用户自发贡献，该文观点与技术仅代表作者本人。本站仅提供信息存储空间服务，不拥有所有权，不承担相关法律责任。如发现本站有涉嫌侵权/违法违规的内容， 请发送邮件至 gblab@vip.qq.com 举报，一经查实，本站将立刻删除。

内容手机端