我想做两个不同的过滤器实现,它只返回那些至少有50%积分的学生。我的问题是如何正确地实现这两种方法,并且在第一次我不明白为什么它不起作用,因此我需要你的帮助。
具有两种实现的过滤器类:
package u7a1;
import java.util.ArrayList;
class Filter implements IFilter {
public ArrayList filterRaw(ArrayList groups)
{
ArrayList<Boolean> allstudents = new ArrayList();
ArrayList<Student> students = new ArrayList();
ArrayList pass = new ArrayList();
for (int i = 0; i < groups.size(); i++)
{
if ((Integer)groups.get(i) >= 50) allstudents.add(true);
else allstudents.add(false);
}
for (int i = 0; i < groups.size(); ++i)
{
if ((Boolean)allstudents.get(i) == true) pass.add(groups.get(i));
}
return pass;
}
public ArrayList<Student> filterGeneric(ArrayList<ArrayList<Student>> groups)
{
ArrayList<Boolean> allstudents = new ArrayList();
ArrayList<Student> students = new ArrayList();
ArrayList pass = new ArrayList();
/*for (int i = 0; i < groups.size(); i++)
{
Integer mystudentpoints = new Integer(0);
mystudentpoints = Student.getPoints();
if (Student.getPoints() >= 50) allstudents.add(true);
else allstudents.add(false);
}*/
for (int i = 0; i < groups.size(); ++i)
{
if ((Boolean)allstudents.get(i) == true) pass.add(groups.get(i));
}
return pass;
}
}
过滤器工厂已经正确:
package u7a1;
/**
* Factory for "Testat" filters
*/
public class FilterFactory {
/**
* Create a "Testat" filter
* @return a "Testat" filter
*/
public static IFilter create()
{
// TODO
return new Filter();
}
}
以下是由方法无法正常工作的类实现的接口:
package u7a1;
import java.util.ArrayList;
/**
* Filters for students who obtain the "Testat".
*
* The requirements for the testat are to have at least {@link IFilter#criteria} percent
* of {@link IFilter#maxNumberofPoints} points.
*/
public interface IFilter {
public final int maxNumberofPoints = 80;
public final double criteria = 50;
/**
* Filter all students that achieved enough points for the "Testat".
*
* @param groups an ArrayList of groups, where a group is an ArrayList of students
* @return the ArrayList of all students who achieved enough points for the "Testat".
*/
public ArrayList filterRaw(ArrayList groups);
/**
* Filter all students that achieved enough points for the "Testat".
*
* @param groups an ArrayList of groups, where a group is an ArrayList of students
* @return the ArrayList of all students who achieved enough points for the "Testat".
*/
public ArrayList<Student> filterGeneric(ArrayList<ArrayList<Student>> groups);
}
我没有进一步编辑主类:
/**
* Main class of the Java program.
*
*/
public class Main {
public static void main(String[] args) {
System.out.println("-- Array-Listen und Generics --");
/* you can make function calls from here*/
}
}
最后,我有一个不需要任何改变的学生课程:
package u7a1;
public class Student {
private String name;
private int legi;
private int points;
public Student(String name, int legi)
{
this.name = name;
this.legi = legi;
points = 0;
}
public int getLegi()
{
return this.legi;
}
public String getName()
{
return this.name;
}
public Student setPoints(int points)
{
this.points = points;
return this;
}
public int getPoints()
{
return points;
}
public String toString()
{
return String.format("%s (%d)", name, legi);
}
}
答案 0 :(得分:0)
你的项目的核心是一个Main.class,有一切将被执行。其他类只是声明,但从不使用它们。运行程序时,它会在main方法中使用命令启动行。目前您唯一拥有的是打印到控制台字符串,带有文本:“ - Array-Listen und Generics - ”
现在您需要准备一些要过滤的数据,例如
Student student1 = new Student("John", 1);
student1.setPoints(51);
Student student2 = new Student("Alice", 2);
student1.setPoints(48);
List<Student> studentList = new ArrayList<>();
studentList.add(student1, student2);
假设您有测试数据,现在需要使用过滤器 要使用您的过滤器,我们需要使用它的实现
IFilter myFilter = FilterFactory.create();
现在myFilter是你的实现的一个实例,要使用它你需要调用一个声明数据的方法
List<Student> result = myFilter.filterRaw(studentList);
该方法的示例实现将是
public List<Student> filteredStudents(List<Student> input) {
return input.stream().filter(s -> s.getPoints() > 50).collect(Collectors.toList());
}
但是您可能会注意到,接口声明中的更改也需要具有相同的类型。
答案 1 :(得分:0)
实现两种类型的过滤行,策略设计模式将有助于你这是一篇好文章http://www.oodesign.com/strategy-pattern.html 而且我认为你必须改变像
这样的填充物 public ArrayList filterRaw(ArrayList groups)
{
ArrayList pass = new ArrayList();
for (int i = 0; i < groups.size(); i++)
{
if ((Integer)groups.get(i) >= 50) pass.add(groups.get(i));
}
return pass;
}