java - 是什么导致我的数组列表中出现此 ArrayOutOfBoundsException？

Question

import java.util.*;
import java.util.ArrayList;

class MyHashTable<K extends Comparable<K>, E> {

    private ArrayList<Entry<K,E>> bucket = new ArrayList<Entry<K,E>>();
    private int bucketSize;
    private int collisionCount = 0;

    // Constructor that takes number of buckets as input
    public MyHashTable( int len ) 
    {
        this.bucketSize = len;
        for ( int i = 0; i < len; i++ ) 
        {
            bucket.set( i, null ); //ERROR APPEARS ON THIS LINE
        }
    }

当我从另一个方法调用时被调用:

MyHashTable<MyString, AnimalRecord> linearProbing = new MyHashTable<MyString, AnimalRecord>(59);
linearProbing.put( lion.name, lion );

Answer 1

private ArrayList<Entry<K,E>> bucket = new ArrayList<Entry<K,E>>();

创建一个空数组列表。

set 方法

Replaces the element at the specified position in this list with the specified element
Throws: IndexOutOfBoundsException - if the index is out of range (index < 0 || index >= size())

所以

bucket.set( i, null );

尝试将 null 设置为 i第 th 个元素(从 0 开始)。但是 arraylist 是空的，这就是你得到异常的原因。

你想要的是 add 方法:

for ( int i = 0; i < len; i++ ) 
{
    bucket.add(null);
}

添加 null到 ArrayList 的结尾.