我创建了一个包含“Student”对象的ArrayList的类，并且我有一个toString方法，用于打印Students测试分数，名称等。但是我一直得到“java.lang.IndexOutOfBoundsException：Index：0，Size：0”这里是我的代码，如果你需要看到更多的代码只是评论
public class School2 {
ArrayList <Student2> studentArray;// array of Student's
/**
* Constructor for School, creates an array of for ten Student's.
*/
public School2() {
final int NUMSTUDENTS = 10;
studentArray = new ArrayList <Student2> (NUMSTUDENTS);
}// end constructor
/**
* Method adds a student 'newStudent' to the array of Student's.
* @param newStudent - Student to be added
*/
public void add(Student2 newStudent) {
studentArray.add(newStudent);
}// end method
/**
* Method adds a Student whose name and test scores are passed in parameter.
* @param name - name of newly added Student
* @param tests - array of test scores belonging to newly added Student
*/
public void add(String name, ArrayList <Integer> testScores) {
Student2 studentAdded = new Student2(name, testScores);
studentArray.add(studentAdded);
}// end method
/**
* Method adds a Student whose name is passed in parameter.
* @param name - name of newly added Student
*/
public void add(String name) {
Student2 studentAdded = new Student2(name);
studentArray.add(studentAdded);
}// end method
/**
* Method adds a Student whose name is an empty String and test scores are 0.
*/
public void add() {
Student2 studentAdded = new Student2();
studentArray.add(studentAdded);
}// end method
/**
* Method removes all Student object 's' from array of Student's
* @param s - Student to be removed from array of Student's
*/
public void remove(Student2 s) {
for (int i = 0; i < studentArray.size(); i++) {
if (studentArray.get(i) == s) {
studentArray.remove(i);
}// end if statement
}// end for loop
}// end method
/**
* Method removes the Student whose index is passed in the parameter
* @param index - index at which the Student is located
*/
public void remove(int index) {
studentArray.remove(index);
}// end method
/**
* Method removes the Student whose name is passed in the parameter
* @param name - name of Student to be removed
*/
public void remove(String name) {
for (int i = 0; i < studentArray.size(); i++) {
if (studentArray.get(i).getName() == name) {
studentArray.remove(i);
}// end if statement
}// end for loop
}// end method
/**
* Method replaces the Student whose index is passed in the parameter with a
* different Student object 'newStudent'
* @param index - index of Student to be replaced
* @param newStudent - Student object to replace other Student
*/
public void replace(int index, Student2 newStudent) {
studentArray.set(index, newStudent);
}// end method
/**
* Method returns the student with the highest test score
* @return - Student with the highest test score
*/
public Student2 getHighScore() {
int index = 0;
int highScore = 0;
for (int i = 0; i < studentArray.size(); i++) {
if (studentArray.get(i).getHighScore() > highScore) {
index = i;
highScore = studentArray.get(i).getHighScore();
}// end if statement
}// end for loop
return studentArray.get(index);
}// end method
/**
* Method returns the class average
*
* @return - class average of test scores
*/
public int getClassAverage() {
int totalScores = 0;
int numTests = 0;
for (int i = 0; i < studentArray.size(); i++) {
for (int x = 1; x <= 3; x++) {
totalScores += studentArray.get(i).getScore(x);
}
numTests += 3;
}// end for loop
return (totalScores / numTests);
}// end method
/**
* Getter method returns a Student whose index is passed in the parameter
* @param index - index of Student object
* @return - Student object
*/
public Student2 getStudent(int index) {
return (studentArray.get(index));
}// end method
/**
* Getter method returns a Student whose name is passed in the parameter
* @param name - name of Student
* @return - Student object
*/
public Student2 getStudent(String name) {
int index = 0;
for (int i = 0; i < studentArray.size(); i++) {
if (studentArray.get(i).getName() == name) {
index = i;
}// end if statement
}// end for loop
return (studentArray.get(index));
}// end method
/**
* Method returns a string containing the names and test scores of all
* students, the class average, and the highest score and the name of the
* student with the highest score.
*/
public String toString() {
String school = "";
for (int i = 0; i < studentArray.size(); i++) {
school += "Name: " + studentArray.get(i).getName() + ":";
//nested for loop gets all 3 tests and concatenates the scores to 'school' string
for (int test = 1; test <= 3; test++) {
school += " test " + test + ": ";
school += studentArray.get(i).getScore(test);
}// end nested for loop
school += " Average: " + studentArray.get(i).getAverage();
school += " High Score: " + studentArray.get(i).getHighScore()
+ "\n";
}// end nested for loop
school += "Class Average: " + getClassAverage() + "\n";
school += "Highest score\n";
school += getHighScore() + "\n";
return school;
}// end method
}//end class
public class Student2
{
String studentName;// name of Student
ArrayList <Integer> studentScores;// test scores of student
final int NUMTESTS = 3;//Student has 3 different test scores
/**
* Constructor for Student2 class, sets name of student to an empty String
* and test scores to 0.
*/
public Student2(){
studentName = "";
studentScores = new ArrayList <Integer> (NUMTESTS);
}//end constructor
/**
* Constructor for Student2 class, sets name to String passed in parameter
* and test scores to 0.
* @param name - name of student
*/
public Student2(String name){
studentName = name;
studentScores = new ArrayList <Integer> (NUMTESTS);
}//end constructor
/**
* Constructor for Student2 class, sets name and test scores to the String
* and array passed in the parameter
*/
public Student2(String name, ArrayList<Integer> testScores){
studentName = name;
studentScores = testScores;
}//end constructor
/**
* Constructor for Student2 class, sets the name and test scores to Student2 's'.
* @param s - Student object
*/
public Student2(Student2 s){
studentName = s.getName();
studentScores = new ArrayList <Integer> (NUMTESTS);
for(int i = 0; i < studentScores.size(); i++){
studentScores.add(s.getScore(i + 1));
}//end for loop
}//end constructor
/**
* Sets name of Student to String passed in parameter
* @param name - name of Student
*/
public void setName(String name) {
studentName = name;
}// end method
/**
* Getter method for Student's name
* @return studentName - name of Student
*/
public String getName() {
return studentName;
}// end method
/**
* Setter method which re-intializes a Student's test score at a given index
* whose values are passed in the parameter
* @param whichTest - test to be set
* @param testScore - value of test to be set
*/
public void setScore(int whichTest, int testScore) {
if (whichTest >= 3) {
studentScores.set(2, testScore);
} else {
studentScores.set((whichTest - 1), testScore);
}
}// end method
/**
* Setter method, re-intializes all test scores to the array passed in the
* parameter
* @param testScores - array of test scores
*/
public void setScore(int[] testScores) {
for(int i = 0; i < testScores.length; i++){
studentScores.set(i, testScores[i]);
}//end for loop
}// end method
/**
* Getter method to get a Student's test score
* @param whichTest - test number
* @return score - score of the particular test number
*/
public int getScore(int whichTest) {
int score = 0;
if (whichTest >= 3) {
score = studentScores.get(2);
} else {
score = studentScores.get((whichTest - 1));
}
return score;
}// end method
/**
* Method calculates the average of the Student's test scores
* @return - average of Student's test scores
*/
public int getAverage() {
int total = 0;
int numTests = 0;
for (int i = 0; i < studentScores.size(); i++) {
total += studentScores.get(i);
numTests++;
}
return (total / numTests);
}// end method
/**
* Method to get the Student's highest test score
* @return highScore - Student's highest test score
*/
public int getHighScore() {
int highScore = 0;
for (int i = 0; i < studentScores.size(); i++) {
if (studentScores.get(i) > highScore) {
highScore = studentScores.get(i);
}//end if statement
}//end for loop
return highScore;
}// end method
/**
* Method returns a String containing the Student's name, test scores,
* average score and high score.
*/
public String toString() {
String student = "Name: " + getName() + ":";
for(int test = 1; test <= studentScores.size(); test++){
student += " test " + test + ": " + getScore(test);
}
student += " Average: " + getAverage();
student += " High Score: " + getHighScore();
return student;
}// end method
}//end class
驱动程序代码：
School2 mySchool = new School2();
ArrayList<Student2> studentArr = mySchool.studentArray;
Student2 s = new Student2("Olive Oyl", randomScores());
mySchool.add(s);
mySchool.add("Popeye", randomScores());
mySchool.add("Bluto");
mySchool.add();
System.out.println(mySchool);
异常消息：
Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
at java.util.ArrayList.rangeCheck(Unknown Source)
at java.util.ArrayList.get(Unknown Source)
at Student2.getScore(Student2.java:107)
at School2.toString(School2.java:176)
at java.lang.String.valueOf(Unknown Source)
at java.io.PrintStream.println(Unknown Source)
at Driver.main(Driver.java:25)`
答案 0 :(得分：0)
for (int test = 1; test <= 3; test++)
这应该是
for (int test = 0; test < 3; test++)
答案 1 :(得分：0)
可能你在这个循环中没有错误，但是在Student类中。 首先尝试这段代码
String school = "";
for (int i = 0; i < studentArray.size(); i++) {
school += "Name: " + studentArray.get(i).getName() + ":\n";
}
return school;
然后尝试将内循环更改为
for (int test = 1; test <= 3; test++) {
school += " test " + test + ": ";
school += studentArray.get(i-1).getScore(test);
}// end nested for loop
因为最有可能的错误就在这里
加。 错误就在这里
public Student2(){
studentName = "";
studentScores = new ArrayList <Integer> (NUMTESTS);
}
，因为
studentScores = new ArrayList <Integer> (NUMTESTS);
不要用4个空整数填充studentScores。 在此行之后，studentScores.size（）返回0 insted of 4
答案 2 :(得分：0)
您的代码中存在一些错误。
请将您的getClassAverage（）方法代码从School2类更新为
public int getClassAverage() {
int totalScores = 0;
int numTests = 0;
for (int i = 0; i < studentArray.size(); i++) {
for (int x = 1; x <= studentArray.get(i).studentScores.size(); x++) {
totalScores += studentArray.get(i).getScore(x);
}
numTests += 3;
}// end for loop
return (totalScores / numTests);
}// end method
还将School2类的toString（）方法改为
public String toString() {
String school = "";
for (int i = 0; i < studentArray.size(); i++) {
school += "Name: " + studentArray.get(i).getName() + ":";
//nested for loop gets all 3 tests and concatenates the scores to 'school' string
for (int test = 1; test <= studentArray.get(i).studentScores.size(); test++) {
school += " test " + test + ": ";
school += studentArray.get(i).getScore(test);
}// end nested for loop
school += " Average: " + studentArray.get(i).getAverage();
school += " High Score: " + studentArray.get(i).getHighScore()
+ "\n";
}// end nested for loop
school += "Class Average: " + getClassAverage() + "\n";
school += "Highest score\n";
school += getHighScore() + "\n";
return school;
}// end method
还要对Student2类的getAverage（）方法进行更改，如下所示：
public int getAverage() {
int total = 0;
int numTests = 0;
for (int i = 0; i < studentScores.size(); i++) {
total += studentScores.get(i);
numTests++;
}
if (numTests == 0) {
return 0;
} else {
return (total / numTests);
}
}// end method
我希望你能从异常投掷的地方得到重点，欢呼。