ArrayIndexOutOfBoundsException，即使我在牢记索引的情况下循环数组，也会收到此奇怪的错误 [英] ArrayIndexOutOfBoundsException, I get this strange error, even when I loop the array keeping in mind the index

问题描述

我知道数组从索引0开始，当我调用数组时，我需要牢记这一点.

I know that arrays start with index zero and, when I call an array, I need to keep this in mind.

例如:

public int name [] = name [3]
for (int i = 0 ; i < 3 ; i++){
    name [i] = 0 ;
}

当我为模型编写代码时，我以相同的方式进行操作.但是，我反复收到错误 java.lang.ArrayIndexOutOfBoundsException .

And I proceed in the same way when I write the code for my model. However, I get the error java.lang.ArrayIndexOutOfBoundsException repeatedly.

这是我的代码:

public int T = 10;
public int A = 100;
public int t = 0;
public int a = 0
public double d  = 2.5;
public double weight = 0;
public double vision; // I initialize this later and it goes smoothly.
public double mem_payoff_time_action[][] = new double [T][A]; 
public double reward_problem[][] = new double [T][A];
public int action_taken[][] = new int [T][A];
public double action_mean []= new double [A]; 


public double getaction_mean() { 
    for ( int p = 0; p < action_mean.length ;p++){
        action_mean[p] = (p + 1);   
    }
    return action_mean[a];
}

public double calculate_mem_payoff_matrix_initialize (){
    for ( int t: Time ){
        for (a = 0 ; a == (action_mean.length - 1) ; a++){
            mem_payoff_time_action[t][a] = 0;
        }
    }
    return mem_payoff_time_action[t][a];
}

public double attach_this_weight(){
    for (a = 0 ; a < A ;a++){
        if (action_taken[t][a] == 1){
            if (vision == 1){
                if (mem_payoff_time_action[t][a] > 0.0 ){
                    weight = 0.1 ;
                }
                else{
                    weight = - (0.1); 
                }
            } 
            if (vision == 2){
                if (mem_payoff_time_action[t][a] > 0.0 ){
                    weight = 0.2 ;
                }
                else{
                    weight   = - (0.2); 
                }
            }
            if (vision == 3){
                if (mem_payoff_time_action[t][a] > 0.0 ){
                    weight = 0.3 ;
                }
                else{
                    weight   = - (0.3); 
                }
            }
        }
    }
    return weight;
}

public double calculate_reward_cummulative(){
    int p= 0;
    if (t ==0){
        for ( a= 0 ; a < action_mean.length ; a++){
            if (a == first_action_index){
                if (mem_payoff_time_action[0][a] < 0){
                    reward_problem[0][a] = d + (weight* mem_payoff_time_action[0][a]); 
                    else{
                        reward_problem[0][a] = d + (weight* mem_payoff_time_action[0][a]);
                    }
                }
                else{
                    reward_problem[0][p] = d;
                }
            }
        }
        else{
            for( p =0; p < action_mean.length  ;p++){
                if(action_taken[t][p]== 1){
                    if(mem_payoff_time_action[t][p] < 0){
                        reward_problem[t][p] = (reward_problem[t-1][p]) + (weight* mem_payoff_time_action[t][p]) ; 
                    }
                    else{
                        reward_problem[t][p] = (reward_problem[t-1][p]) + (weight* mem_payoff_time_action[t][p]) ;
                    }
                }
                else{
                    reward_problem[t][p] = reward_problem[t-1][p]; 
                }
            }
        }
        return reward_problem[t][a];
    }

我在方法 calculate_reward_cummulative

而且，我的大多数代码都不断收到此错误.

And, I keep getting this error for most of my code.

我在 mem_payoff_time_action [] [] 上收到了相同的错误.我在写:

I was receiving the same error formem_payoff_time_action[][]. I was writing:

for (t = 0; t< T; t++){
    for (a = 0; a < A ; a++){
        mem_payoff_time_action[t][a] = 0;
    }
}

为了解决该错误，我用 action_mean.length 更改了'A'.而且，我创建了一个名为时间的数组.

In order to fix the error, I change 'A' with action_mean.length. And, I created an array called Time.

public int Time [] = new int [T];
public int calcualte_time (){
    for (int t : Time){
        Time [t] = 0;
    }
    return Time [t];
}

而且，我重写了下面提到的代码.而且，一切都很好.但是，我仍然不明白为什么会出现此错误.

And, I rewrote the code as mentioned below. And, everything was fine. However, I still don't understand why I get this error.

推荐答案

正如您正确指出的那样，您得到的错误是在calculate_reward_cummulative方法中，原因如下:

as you rightly pointed out the error you are getting is in calculate_reward_cummulative method, the reason being the following:

返回reward_problem [t] [a];

return reward_problem[t][a];

该数组在逻辑上将具有10行(索引0-9)和100列(索引0-99).如果您尝试获取第100个索引的值，则肯定会遇到此异常.

the array will logically have 10 rows (index 0-9) and 100 columns (index 0-99). if you try to get the value for the 100th index, you are bound to get this exception.

这里t变为0，但是a作为全局变量，您将其用作for循环中的计数器，

here t is coming as 0 but as a is a global variable and you are using it as a counter in the for loop,

for(a = 0; a< action_mean.length; a ++)

for ( a= 0 ; a < action_mean.length ; a++)

当循环结束时，计数器的值(即"a")为100，因此您试图返回reward_problem [0] [100]，因此jvm抛出异常.

when the loop ends the value of the counter ie "a" is 100, thus you are trying to return reward_problem[0][100], thus jvm is throwing exception.

请尝试使用其他计数器变量并返回适当的数组索引.

please try to use a different counter variable and return the appropriate array index.

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