为什么私有化List后用get调用的时候调不了
荷包蛋的忧伤
2019-07-27 17:27
package com.student;
import java.util.ArrayList;
import java.util.List;
public class ListTest {
private List coursesToSelect;
public List getCoursesToSelect() {
return coursesToSelect;
}
public void setCoursesToSelect(List coursesToSelect) {
this.coursesToSelect = coursesToSelect;
}
public ListTest(){
this.coursesToSelect=new ArrayList();
}
public void testAdd(){
Course cr1=new Course("1", "人类起源学");
coursesToSelect.add(cr1);
Course temp=(Course) getCoursesToSelect();//这边输0会报错
System.out.println("输入进的课程："+temp.getId()+"-"+temp.getName());
}
public static void main(String[] args) {
// TODO 自动生成的方法存根
ListTest lt=new ListTest();
lt.testAdd();
}Exception in thread "main" java.lang.ClassCastException: java.util.ArrayList cannot be cast to com.student.Course at com.student.ListTest.testAdd(ListTest.java:20) at com.student.ListTest.main(ListTest.java:26)
3回答
-
- DE先森
- 2019-07-28 18:40:09
一开始以为你设了private属性，然后直接调用发生错误，但看代码，有用public方法返回列表，妥的；
发现，你没用get（）方法来获取录入的课程信息。多打代码，注意自己和老师代码是否一致。
-
- 荷包蛋的忧伤
- 2019-07-27 17:31:37
Exception in thread "main" java.lang.ClassCastException: java.util.ArrayList cannot be cast to com.student.Course
at com.student.ListTest.testAdd(ListTest.java:20)
at com.student.ListTest.main(ListTest.java:26)
-
- 荷包蛋的忧伤
- 2019-07-27 17:31:09
package com.student;
import java.util.ArrayList;
import java.util.List;
public class ListTest {
private List coursesToSelect;
public List getCoursesToSelect() {
return coursesToSelect;
}
public void setCoursesToSelect(List coursesToSelect) {
this.coursesToSelect = coursesToSelect;
}
public ListTest(){
this.coursesToSelect=new ArrayList();
}
public void testAdd(){
Course cr1=new Course("1", "人类起源学");
coursesToSelect.add(cr1);
Course temp=(Course) getCoursesToSelect();
System.out.println("输入进的课程："+temp.getId()+"-"+temp.getName());
}
public static void main(String[] args) {
// TODO 自动生成的方法存根
ListTest lt=new ListTest();
lt.testAdd();
}
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