Java 从LinkedList中检索特定数据

我想通过使用streams找到性别为女性的学生

学生

班级

public class Student {
    private String first;
    private String last;
    private int ID;
    private Gender gender;

    int next=0;

    List<Course> courses=new LinkedList<>();
    List<Student> students=new LinkedList<>();

    public Student(String first, String last, int iD, Gender gender) {
        this.first = first;
        this.last = last;
        ID = iD;
        //this.gender = gender;
    }

    public void enroll(Course c) {
        courses.add(c);
    }

    public void isFemale(){
        Student s;
        return s.gender=Gender.F;
    }
}

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

        List<Student> studentsOfClass=new LinkedList<>();

        studentsOfClass.add(new Student("john","smith",01,Gender.M));
        studentsOfClass.add(new Student("mick","tayson",05,Gender.M));
        studentsOfClass.add(new Student("sara","conor",04,Gender.F));
        studentsOfClass.add(new Student("Tana","smith",02,Gender.F));

        Course c1=new Course("fiologiya","anna",0234);
        Course c2=new Course("mathematics","maria",1134);
        Course c3=new Course("phisics","luisa",0534);

        studentsOfClass.stream().limit(3).forEach(s->s.enroll(c1));

        Collection<Student> femaleStudents= studentsOfClass.stream().filter(Student::isFemale).collect(Collectors.toList());

    }
}

main

class

public class Student {
    private String first;
    private String last;
    private int ID;
    private Gender gender;

    int next=0;

    List<Course> courses=new LinkedList<>();
    List<Student> students=new LinkedList<>();

    public Student(String first, String last, int iD, Gender gender) {
        this.first = first;
        this.last = last;
        ID = iD;
        //this.gender = gender;
    }

    public void enroll(Course c) {
        courses.add(c);
    }

    public void isFemale(){
        Student s;
        return s.gender=Gender.F;
    }
}

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

        List<Student> studentsOfClass=new LinkedList<>();

        studentsOfClass.add(new Student("john","smith",01,Gender.M));
        studentsOfClass.add(new Student("mick","tayson",05,Gender.M));
        studentsOfClass.add(new Student("sara","conor",04,Gender.F));
        studentsOfClass.add(new Student("Tana","smith",02,Gender.F));

        Course c1=new Course("fiologiya","anna",0234);
        Course c2=new Course("mathematics","maria",1134);
        Course c3=new Course("phisics","luisa",0534);

        studentsOfClass.stream().limit(3).forEach(s->s.enroll(c1));

        Collection<Student> femaleStudents= studentsOfClass.stream().filter(Student::isFemale).collect(Collectors.toList());

    }
}

公共类主{
公共静态void main（字符串[]args）{
列出studentsOfClass=new LinkedList（）；
添加（新学生（“约翰”，“史密斯”，01，性别M））；
添加（新学生（“mick”，“tayson”，05，性别M））；
添加（新学生（“sara”，“conor”，04，性别F））；
添加（新学生（“塔娜”，“史密斯”，02，性别F））；
课程c1=新课程（“fiologiya”，“anna”，0234）；
课程c2=新课程（“数学”，“玛丽亚”，1134）；
课程c3=新课程（“物理”、“路易莎”，0534）；
studentsOfClass.stream（）.limit（3.forEach（s->s.enroll（c1））；
Collection FemalesStudents=studentsOfClass.stream（）.filter（Student:：isFemale.collect（Collectors.toList（））；
}
}

您正确地使用了流方法，但您的isFamele方法是错误的。它应该返回布尔值并检查当前学生的性别

应该是：

public boolean isFemale() 
{
    return gender==Gender.F;
}

您还应该取消标记此构造函数行-

//this.gender=gender-并可能删除
私人性别来自性别枚举

此外，您可以将
femaleStudents
的类型从
Collection
更改为
List
，这更准确。
为什么您的性别枚举有性别字段？？