為什么課程添加不進去
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>();
????}
????/**
?????*?添加備選課程
?????*/
????public??void?testAdd(){
????????//創建課程對象,并通過調用add方法添加到備選課程List
????????Course?course01?=?new?Course("002","c語言");
????????coursesToSelect.add(course01);
????????//對象存入集合時都變成Object類型,取出時也是object需要轉換類型
????????Course?temp?=?(Course)?coursesToSelect.get(0);
????????System.out.println("添加了課程:"?+?temp.id?+?":"?+temp.name);
????????Course?course02?=?new?Course("001","高等數學");
????????coursesToSelect.add(0,course02);
????????Course?temp01?=?(Course)?coursesToSelect.get(0);
????????Course?temp03?=?(Course)?coursesToSelect.get(0);
????????Course[]?courses?=?{new?Course("003","近代詩"),new?Course("004","計算機導論")};
????????coursesToSelect.addAll(Arrays.asList(courses));
????????Course?temp02?=?(Course)?coursesToSelect.get(2);
????}
????/**
?????*?通過for?each方法訪問集合元素
?????*
?????*?@param
?????*/
????public?void?testForEachForSet(Student?student){
????????//?打印輸出,學生所選的課程!
????????System.out.println("共選擇了:"?+?student.courses.size()?+?"門課程!");
????????for?(Course?cr?:?student.courses)?{
????????????System.out.println("選擇了課程:"?+?cr.id?+?":"?+?cr.name);
????????}
????}
????public?static??void?main(String[]?args)?{
????????SetTest?st?=?new?SetTest();
????????st.testAdd();
????????st.testForEach();
????????Student?student?=?new?Student("1","水水");
????????System.out.println("歡迎學生:"+student.name?+"選課");
????????Scanner?console?=?new?Scanner(System.in);
????????for?(int?i?=0?;?i<3;i++){
???????????System.out.println("輸入課程ID");
???????????String?courseId?=?console.next();
????????????for?(Course?cr:st.coursesToSelect)?{
????????????????if?(cr.id.equals(courseId)){
????????????????????student.courses.add(cr);
????????????????}
????????????}
????????????st.testForEachForSet(student);
????????}
????}
????public?void?testForEach()?{
????????System.out.println("有如下課程待選(通過for?each訪問):");
????????for?(Object?obj?:?coursesToSelect)?{
????????????Course?cr?=?(Course)?obj;
????????????System.out.println("課程:"?+?cr.id?+?":"?+?cr.name);
????????}
????}
}提示選擇了0門課程
2019-07-19
這頁ADD好像沒什么問題 是不是其他類設置出了問題
2019-03-19
編號問題
2018-11-21
會不會是你在定義coursesToSelect變量時已經定義為Course泛型變量了,后面不需要轉換類型了,試試