Set集合

package com.imooc.collection;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Scanner;

public class SetTest {
    public List<Course> coursesToSelect;

    public SetTest(){
        coursesToSelect = new ArrayList<Course>();
    }
    /** * 用于往coursesToSelect中添加备选课程 */
    public void testAdd(){
        //创建一个课程对象，并通过调用add方法，添加到备选课程List中
        Course cr1 = new Course("1","数据结构");
        coursesToSelect.add(cr1);
        //取出元素  get方法
        Course temp = (Course)coursesToSelect.get(0);
        //System.out.println("添加了课程："+temp.id+":"+temp.name);

        Course cr2 = new Course("2","C语言");//提供索引位置，插入元素
        coursesToSelect.add(0, cr2);
        Course temp2 = (Course)coursesToSelect.get(0);
        //System.out.println("添加了课程："+temp2.id+":"+temp2.name);

        coursesToSelect.add(cr1);
        //取出元素  get方法
        Course temp0 = (Course)coursesToSelect.get(2);
        //System.out.println("添加了课程："+temp.id+":"+temp.name);

        //以下方法会抛出数组下标越界异常
        //Course cr3 = new Course("3","Test");
        //coursesToSelect.add(4,cr3);数组越界

        Course[] course = {new Course("3","离散数学"),new Course("4","汇编语言")};
        coursesToSelect.addAll(Arrays.asList(course));
        Course temp3 = (Course)coursesToSelect.get(3);
        Course temp4 = (Course)coursesToSelect.get(4);

        //System.out.println("添加了两门课程："+temp3.id+":"+temp3.name+";"+temp4.id+":"+temp4.name);

        Course[] course2 = {new Course("5","高等数学"),new Course("6","大学英语")};
        coursesToSelect.addAll(2,Arrays.asList(course2));
        Course temp5 = (Course)coursesToSelect.get(2);
        Course temp6 = (Course)coursesToSelect.get(3);

        //System.out.println("添加了两门课程："+temp5.id+":"+temp5.name+";"+temp6.id+":"+temp6.name);

    }
    /** * 通过for each方法访问集合元素 * @param args */
    public void testForEach(){
        System.out.println("有如下课程待选（通过for each访问）：");
        for(Object obj:coursesToSelect){
            Course cr = (Course)obj;
            System.out.println("课程："+cr.id+":"+cr.name);
        }
    }
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        SetTest st = new SetTest();
        st.testAdd();
        st.testForEach();
        //创建一个学生对象
        Student student = new Student("1","小王");
        System.out.println("欢迎学生："+student.name+"选课！");
        //创建要给Scanner对象，用来接收从键盘输入的课程ID 
        Scanner console = new Scanner(System.in);
        for(int i=0;i<3;i++){
    
            System.out.println("请输入课程ID");
            String courseId = console.next();
            for(Course cr:st.coursesToSelect){
                if(cr.id.equals(courseId)){
                    student.courses.add(cr);
                    /** * Set中，添加某个对象，无论添加多少次 * 最终只会保留一个该对象(的引用）, * 并且，保留第一次添加的那一个 */
                    //student.courses.add(cr);
                    //student.courses.add(null);
                }
            }
        }
        st.testForEachForSet(student);
    }
    public void testForEachForSet(Student student){
        //打印输出，学生所选的课程！
        System.out.println("供选择了："+student.courses.size());
        for(Course cr:student.courses){
            System.out.println("选择了课程："+cr.id+":"+cr.name);
        }
    }

}