为什么会抛出IndexOutOfBoundsException?
问题描述:
为什么在以下代码段中抛出IndexOutOfBoundsException? 我似乎无法理解为什么它被抛出?为什么会抛出IndexOutOfBoundsException?
import java.util.*;
public class PrimeNumbers {
//Printing all prime numbers less than 600 using 'Sieve Method'
final static int SIZE = 600;
static ArrayList<Integer> numbers = new ArrayList<Integer>(SIZE);
public static void populateList(ArrayList<Integer> arraylist){
for(int i=0; i<SIZE; i++){
arraylist.add(i, i);
}
}
public static void filterMultiples(ArrayList<Integer> arraylist){
for(int i=0; i<SIZE; i++){
if(arraylist.get(i)%2==0 || arraylist.get(i)%3==0 || arraylist.get(i)%5==0){
arraylist.remove(i);
}
}
}
public static void main(String[] args){
populateList(numbers);
filterMultiples(numbers);
System.out.println(numbers);
}
}
堆栈跟踪:
Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 300, Size: 300
at java.util.ArrayList.rangeCheck(ArrayList.java:653)
at java.util.ArrayList.get(ArrayList.java:429)
at PrimeNumbers.filterMultiples(PrimeNumbers.java:17)
at PrimeNumbers.main(PrimeNumbers.java:25)
答
for(int i=0; i<SIZE; i++){
if(arraylist.get(i)%2==0 || arraylist.get(i)%3==0 || arraylist.get(i)%5==0){
arraylist.remove(i);
}
}
}
你迭代从0到SIZE
,但移除元素会导致那里是在列表中少于SIZE
元素。
答
该错误是在该块中:
for(int i=0; i<SIZE; i++){
if(arraylist.get(i)%2==0 || arraylist.get(i)%3==0 || arraylist.get(i)%5==0){
arraylist.remove(i);
}
}
}
当你通过数组列表迭代,则从中删除元素。因此,它变得更短,尺寸变得比实际尺寸(600)小。
请尝试使用迭代器。它们在迭代时支持修改:
for (Iterator<Integer> iterator = numbers.iterator(); iterator.hasNext();) {
int number = iterator.next();
if (number % 2 == 0 || number % 3 == 0
|| number % 5 == 0) {
iterator.remove();
}
}