是System.out.println；你試一下；不是System.err.println；

附上代碼

package?com.集合類;
import?java.lang.reflect.Array;
import?java.util.ArrayList;
import?java.util.Arrays;
import?java.util.List;
//備選課程
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?textAdd(){
//創(chuàng)建一個(gè)課程對(duì)象，并通過調(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)");
coursesToSelect.add(cr1);
Course?temp?=?(Course)?coursesToSelect.get(0);
System.err.println("添加一個(gè)課程:"+temp.id+":"+temp.name);
Course?cr2?=?new?Course("2",?"c語音");
coursesToSelect.add(0,cr2);
Course?temp2?=?(Course)?coursesToSelect.get(0);
System.out.println("添加一個(gè)課程:"+temp2.id+":"+temp2.name);
//一下方法會(huì)拋出數(shù)組下標(biāo)越界異常
//Course?cr3?=?new?Course("3",?"text");
//coursesToSelect(4,cr3);
Course[]?course?=?{new?Course("3",?"離散數(shù)學(xué)"),new?Course("4",?"匯編語言")};
coursesToSelect.addAll(Arrays.asList(course));
Course?temp3?=?(Course)?coursesToSelect.get(2);
Course?temp4?=?(Course)?coursesToSelect.get(3);
System.err.println("添加兩個(gè)課程:"+temp3.id+":"+temp3.name+temp4.id+":"+temp4.name);
Course[]?course2?=?{new?Course("5",?"大學(xué)數(shù)學(xué)"),new?Course("6",?"大學(xué)語言")};
coursesToSelect.addAll(2,Arrays.asList(course2));
Course?temp5?=?(Course)?coursesToSelect.get(2);
Course?temp6?=?(Course)?coursesToSelect.get(3);
System.err.println("添加兩個(gè)課程:"+temp5.id+":"+temp5.name+temp6.id+":"+temp6.name);
}
//取得List中的元素的方法
public?void?testGet(){
int?size?=?coursesToSelect.size();
System.out.println("有如下課程待選:");
for(int?i=0;i<size;i++){
Course?cr?=?(Course)?coursesToSelect.get(i);
System.err.println("課程:"+cr.id+":"+cr.name);
}
}
public?static?void?main(String[]?args)?{
ListTest?lt?=?new?ListTest();
lt.textAdd();
lt.testGet();
}
}