集合框架學(xué)生選課提示數(shù)組下標(biāo)越界
按照老師說的輸入的提示：
這個(gè)提示是數(shù)組下標(biāo)越界的意思吧，但是我是按照視頻里代碼輸入的，包括導(dǎo)入包都沒有錯(cuò)誤，不知道為什么出現(xiàn)這個(gè)提示。
Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 0, Size: 0 ? ?
不知道為什么？
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2017-05-25
Course cr1 = new Course("1","數(shù)據(jù)結(jié)構(gòu)");
Course temp = (Course) coursesToSelect.get(0);
coursesToSelect.add(cr1);
順序錯(cuò)了，代碼執(zhí)行是按照寫的順序來的，你還沒加進(jìn)去就要取出來，肯定不對(duì)，把?coursesToSelect.add(cr1); 跟
Course temp = (Course) coursesToSelect.get(0);調(diào)換一下順序就可以了。
2017-05-19
寫的代碼如下：
package com.imooc.collection;
/**
?* 課程類
?* @author Administrator
?*
?*/
public class Course {
public String id;
public String name;
public Course(String id,String name){
this.id = id;
this.name = name;
}
}
=================================================
package com.imooc.collection;
import java.util.HashSet;
import java.util.Set;
/**
?* 學(xué)生類
?* @author Administrator
?*
?*/
public class Student {
public String id;
public String name;
public Set courses;
public Student(String id,String name){
this.id = id;
this.name = name;
this.courses = new HashSet();
}
}
======================================
package com.imooc.collection;
import java.util.List;
import java.util.ArrayList;
/**
?* 備選課程類
?* @author Administrator
?*
?*/
public class ListTest {
/**
* 用于存放備選課程的list
*/
public List coursesToSelect;
public ListTest(){
this.coursesToSelect = new ArrayList();
}
/**
* 用于往coursesToSelect中添加備選課程
*/
public void testAdd(){
//創(chuàng)建一個(gè)課程對(duì)象，并且通過調(diào)用add方法，添加到備選課程list中
Course cr1 = new Course("1","數(shù)據(jù)結(jié)構(gòu)");
Course temp = (Course) coursesToSelect.get(0);
coursesToSelect.add(cr1);
System.out.println("添加了課程:"+temp.id+":"+temp.name);
Course cr2 = new Course("2","C語言");
coursesToSelect.add(0,cr2);
Course temp2 = (Course)coursesToSelect.get(0);
System.out.println("添加了課程:"+temp2.id+":"+temp2.name);
}
public static void main(String[] args){
ListTest lt = new ListTest();
lt.testAdd();
}
}