感觉最后多了个 }

你把testForEachForSet方法放到main方法前面试试

package com.test.collection;

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

public class SetTest {

    public List<Course> coursesToSelect;
    //构造器
    public SetTest(){
        coursesToSelect=new ArrayList<Course>();
    }

/*    public static class List_Test {
        //用于存放备选课程的List
        public List coursesToSelect;

        public List_Test(){
            this.coursesToSelect=new ArrayList();
        }
        }*/
        //用于网coursesToSelet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，添加到备选课程中
            Course cr1=new Course("1","数据结构");
            coursesToSelect.add(cr1);
            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："+temp.id+";"+temp.name);

            //下面方法会抛出数组下标越界异常
            // Course cr3=new Course("3","test");
            //coursesToSelect.add(4,cr3);

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

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

            Course[] courses2={new Course("5","高等数学"),new Course("6","大学英语")};
            coursesToSelect.addAll(2,Arrays.asList(courses2));
            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);

        }


        /*
        for each方法访问集合元素  更好
         */
        public void testForEach(){
            System.out.println("有如下课程待选（通过foreach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) {
            SetTest st=new SetTest();
            st.testAdd();
            st.testForEach();
            Student student=new Student("1","小埋");
        System.out.println("欢迎学生 "+student.name+"选课");
        //创建一个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("输入课程ID");
            String courseId=console.next();
            for (Course cr:st.coursesToSelect){
                if (cr.id.equals(courseId)){
                    student.courses.add(cr);
                }
            }
        }
        st.testForEachForSet(student);
    }
    public void testForEachForSet(Student student){
            //打印输出 学生所选的课程
        System.out.println("xuanle" +student.courses.size()+"ke");
        for (Course cr:student.courses){
            System.out.println("选择了课程 "+cr.id+":"+cr.name);
        }
    }
    }