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為何會越界異常

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>();

}

public void testAdd() {

/*

* 創建一個課程對象,并通過調用add方法,添加到備選課程List中

*/

Course cr1 = new Course("1","數據結構");

coursesToSelect.add(cr1);

Course temp = (Course) coursesToSelect.get(0);

// 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(1);?

// System.out.println("添加了課程:" + temp2.id + ":" +temp2.name);

// coursesToSelect.add(cr1);

// Course temp0 = (Course) coursesToSelect.get(0);

// System.out.println("添加了課程:" + temp.id + temp.name);

//以下方法會拋出數組下標越界異常

// Course cr3 = new Course("3","test");

// coursesToSelect.add(4, cr3);

Course course[] = {new Course("3","離散數學"), new Course("4","匯編語言")};

coursesToSelect.addAll(Arrays.asList(course));

Course temp3 = (Course) coursesToSelect.get(3);

Course temp4 = (Course) coursesToSelect.get(4);

// System.out.println("添加了2門課程" + temp3.id + ":" +

// temp3.name + ";" + temp4.id + ":" + temp4.name);

Course course2[]= {new Course("5","高等數學"), new Course("6","大學英語")};

coursesToSelect.addAll(2, Arrays.asList(course2));

Course temp5 = (Course) coursesToSelect.get(2);

Course temp6 = (Course) coursesToSelect.get(3);


// System.out.println("添加了兩門課程"+ temp5.id + ":" +temp5.name +

// temp6.id + ":" + temp6.name);

}


public void testForEach() {

System.out.println("有以下課程待選(通過for each返回):");

for(Object obj:coursesToSelect) {

Course cr = (Course) obj;

System.out.println("課程:" + cr.id + ":" + cr.name);

}

}


public static void main(String[] args) {

// TODO Auto-generated method stub

SetTest st = new SetTest();

st.testAdd();

st.testForEach();

//創建一個新的學生對象

Student student = new Student("1","小明");

System.out.println("歡迎學生:" + student.name + "選課");

//創建一個scanner對象,用來接收用鍵盤輸入的課程ID

Scanner console = new Scanner(System.in);

for(int i = 0; i < 3; i++) {

System.out.println("請輸入課程ID:");

String courseId = console.next();

for (Course cr : st.coursesToSelect) {

if(cr.id.equals(courseId)) {

student.courses.add(cr);

}

}

}

st.testForEachForSet(student);

}

public void testForEachForSet(Student student) {

//打印輸出學生所選課程

for(Course cr : student.courses) {

System.out.println("選擇了課程" + cr.id + cr.name);

}

}

}


正在回答

1 回答

把這句注釋掉就好了~?

Course temp4 = (Course) coursesToSelect.get(4);



0 回復 有任何疑惑可以回復我~

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