5.学生选课，课程修改

package com.imooc.collection;

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

/**
 * 备选课程类
 *
 * @author Administrator
 *
 */
public class ListTest {
    /*
     * 用于存放备选课程的List
     */
    public List coursesToSelect;

    public ListTest() {
        this.coursesToSelect = new ArrayList();
    }

    /*
     * 用于往coursesToSelect中添加备选课程
     */
    public void testAdd() {
        // 创建一个对象，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);
        // 注意：对象存入集合都变成Object类型，取出时需要类型转换，强转
        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");
        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);
        Course temp0 = (Course) coursesToSelect.get(2);
        System.out.println("添加了课程-->" + temp0.id + ":" + temp0.name);

        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);
    }

    /**
     * 取得List中的元素的方法
     *
     * @param args
     */

    public void testGet() {
        int size = coursesToSelect.size();
        System.out.println("有如下课程可选：");
        for (int i = 0; i < size; i++) {
            Course cr = (Course) coursesToSelect.get(i);
            System.out.println("课程-->" + cr.id + cr.name);
        }
    }

    /*
     * 通过迭代器来遍历List
     */

    public void testIterator() {
        // 通过集合的iterator方法，取得迭代器的实例
        Iterator it = coursesToSelect.iterator();
        System.out.println("有如下课程可以选择（通过迭代器访问）：");
        while (it.hasNext()) {
            Course cr = (Course) it.next();
            System.out.println("课程：" + cr.id + cr.name);
        }
    }

    /*
     * 通过for each方法访问集合元素
     */

    public void testForEach() {
        System.out.println("有如下课程可以选择（通过foreach访问）：");
        for (Object obj : coursesToSelect) {
            Course cr = (Course) obj;
            System.out.println("课程：" + cr.id + cr.name);
        }
    }

    /**
     * 修改List中的元素
     *
     * @param args
     */

    public void testModify() {
        coursesToSelect.set(4, new Course("7", "毛概"));
    }

    public static void main(String[] args) {
        ListTest lt = new ListTest();
        lt.testAdd();
        lt.testGet();
        lt.testIterator();
        lt.testForEach();
        lt.testModify();
        lt.testForEach();
    }
}