集合题目1

集合题目：
1，定义一个Course类，代表课程；定义一个Student类，代表学生，在Student类中包含一个属性是一个HashSet的对象，用来存储该学生所选的所有课程，并提供相应的addCourse(Course c)方法
2，定义一个类SchoolClass代表班级，该类中包含一个属性是一个HashSet的对象，用来存储该班级中所有的Student,并提供相应的addStudent(Student s)方法
3，在主方法中生成一个SchoolClass对象，添加若干个学生，并且为每个学生添加若干门课程，最后要统计出每门课程的选课人数。（随机）

Course类：

package exercise3;

public class Course {
	private String cname;

	public String getCname() {
		return cname;
	}

	public void setCname(String cname) {
		this.cname = cname;
	}

	public Course(String cname) {
		this.cname = cname;
	}

	public boolean equals(Object o) {
		if (o instanceof Course) {
			Course c = (Course) o;
			if (c.cname.equals(this.cname)) {
				return true;
			}
		}
		return false;
	}

	public int hashCode() {
		return this.cname.hashCode();
	}

	@Override
	public String toString() {
		StringBuffer sb = new StringBuffer();
		return sb.append(cname).toString();
	}
}

 Student类：

package exercise3;

import java.util.HashSet;

public class Student {
	private String sname;
	private HashSet<Course> courses;

	// 构造方法
	public Student(String sname) {
		this.sname = sname;
		courses = new HashSet<Course>();
	}

	// 增加课程
	public boolean addCourse(Course c) {
		return courses.add(c);
	}

	public String getSname() {
		return sname;
	}

	public void setSname(String sname) {
		this.sname = sname;
	}

	public HashSet<Course> getCourses() {
		return courses;
	}

	public void setCourses(HashSet<Course> courses) {
		this.courses = courses;
	}

	public boolean equals(Object o) {
		if (o instanceof Student) {
			Student s = (Student) o;
			if (s.sname.equals(this.sname)) {
				return true;
			}
		}
		return false;
	}

	public int hashCode() {
		return this.sname.hashCode();
	}

	@Override
	public String toString() {
		StringBuffer sb = new StringBuffer();
		return sb.append("Student [Sname=").append(sname).append(courses)
				.append("]").toString();
	}

}

 

 

SchoolClass类：

package exercise3;

import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

public class SchoolClass {
	private String name;
	private HashSet<Student> students;// 班级中所有的学生

	public SchoolClass(String name) {
		this.name = name;
		students = new HashSet<Student>();
	}

	public boolean addStudent(Student s) {
		return students.add(s);
	}

	public Map<Course, Integer> account() {// 统计每门课程的选课人数,key代表课程，value代表人数。
		Map<Course, Integer> map = new HashMap<Course, Integer>();
		Iterator<Student> it = students.iterator();
		while (it.hasNext()) {// 遍历所有学生
			Student stu = it.next();
			Iterator<Course> is = stu.getCourses().iterator();
			while (is.hasNext()) {// 遍历每个学生所选的课程
				Course c = is.next();
				map.put(c, map.get(c) == null ? 1 : map.get(c) + 1);
			}
		}
		return map;
	}

	public void printCount() {
		Set<Course> set = account().keySet();
		Iterator<Course> it = set.iterator();
		while (it.hasNext()) {
			Object key = it.next();
			System.out.println(key + "," + account().get(key));
		}
	}
}

 

Test测试类：

package exercise3;

import java.util.HashSet;
import java.util.Iterator;
import java.util.Random;

public class Test {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		Course[] course = { new Course("Java语言"), new Course("高数"),
				new Course("英语"), new Course("数据库") };

		SchoolClass class1 = new SchoolClass("Class1");
		for (int i = 0; i < 20; i++) {
			Student stu = new Student("Student-" + (i + 1));
			int num = (int) (Math.random() * course.length);
			for (int j = 0; j < num; j++) {
				stu.addCourse(course[(int) (Math.random() * course.length)]);
			}
			class1.addStudent(stu);
			System.out.println(stu);
		}
		System.out.println("==================================");

		class1.printCount();
	}
}

 

运行结果：

Student [Sname=Student-1[]]
Student [Sname=Student-2[]]
Student [Sname=Student-3[Java语言]]
Student [Sname=Student-4[数据库]]
Student [Sname=Student-5[Java语言, 英语, 高数]]
Student [Sname=Student-6[英语, 数据库]]
Student [Sname=Student-7[]]
Student [Sname=Student-8[Java语言, 英语]]
Student [Sname=Student-9[数据库]]
Student [Sname=Student-10[高数]]
Student [Sname=Student-11[英语, 高数]]
Student [Sname=Student-12[Java语言]]
Student [Sname=Student-13[]]
Student [Sname=Student-14[英语]]
Student [Sname=Student-15[数据库, 英语]]
Student [Sname=Student-16[英语, Java语言, 数据库]]
Student [Sname=Student-17[]]
Student [Sname=Student-18[]]
Student [Sname=Student-19[英语]]
Student [Sname=Student-20[英语]]
==================================
数据库,5
Java语言,5
英语,9
高数,3