NullPointerException异常数组 [英] NullPointerException in array

问题描述

我不断收到的（见下文）一个NullPointerException异常。一切工作在C＃罚款，但在android系统它打破？

arrDBNumbers已满，code被认为通过运行和计数的＃1的量，＃2，＃3等至＃49加入1〜arrFreq [Ⅰ] [1]，以填补该arrFreq数的总数。

它贯穿if语句，直到ķ命中6中，其中arrDBNumbers [0] [6]为1，然后跳转内if语句，然后休息？我不知道怎么回事就在这里的任何建议
在此先感谢牛逼

 整数[] [] = arrDBNumbers新的整数[100]; [8]
整数[] [] arrFreq =新的整数[49] [2];
的for（int i = 0; I＆LT; 49;我++）{
    对于（INT J = 0; J＆LT; 49; J ++）{
        为（中间体K = 1; K＆7;; k ++）{
            如果（arrDBNumbers [j]的[K] ==第（i + 1））{
                arrFreq [I] [1] ++; //＆LT;这里是我得到异常？
            }
        }
    }
}
 

解决方案

由于只是写

 整数[] [] = arrFreq新的整数[49] [2];
 

的表示您已初始化所有的空元素的数组，因为它是整数数组对象并对象的默认值是空引用。的
因此，

  arrFreq [I] [1] ++; //尝试空++;
 

给 NullPointerException异常。

这不会有，如果你曾使用情况下的元的阵列，这将默认为 0 组成的数组。的

  INT [] [] = arrFreq新INT [49] [2];
 

I keep getting a NullPointerException at (see below). Everything works fine in C#, but in android it breaks?

arrDBNumbers is full and code is supposed to run through and count the amount of #1, #2, #3 and so on to #49 adding 1 to arrFreq[i][1] to fill arrFreq with the total count of the numbers.

It runs through the if statement till k hits 6 where arrDBNumbers[0][6] is 1, then jumps inside if statement and then breaks? I'm not sure whats going on here any advice thanks in advance T

Integer[][] arrDBNumbers = new Integer[100][8];
Integer[][] arrFreq = new Integer[49][2];


for (int i = 0; i < 49; i++){
    for (int j = 0; j < 49; j++){
        for (int k = 1; k < 7; k++){
            if (arrDBNumbers[j][k] == (i + 1)){
                arrFreq[i][1]++;     //  < here is where I get Exception?
            }
        }
    }
}

解决方案

Because just writing

Integer[][] arrFreq = new Integer[49][2];

means you have initialized the array with all null elements because it is an array of Integer Objects and Object's default value will be null reference. Hence,

arrFreq[i][1]++;  // trying null++;

gives NullPointerException.

This wouldn't have been the case if you had used an array of primitives, which will default to an array of 0s.

int[][] arrFreq = new int[49][2];

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