java - 它告诉我 NullPointerException 的原因

Question

为什么这会给我 NullpointerException 错误？它发生在我的代码的第三行，所以我的第一个 for 循环。正如您所知，这是一种可以访问较大代码的其他部分的方法。

public static void insertionsort() 
{
    for (int outer = 1; outer < array.length; outer++)//Outer=next number to be sorted 
    { 
        String temp = array[outer]; //Stores it for later use
        int inner = outer; // inner used to track shifts 
        while (inner > 0 && array[inner - 1].compareTo(temp) >= 0) 
        {  
            array[inner] = array[inner - 1];//Swaps the number
            inner--;// Decrements
        } //shift them all right until one is smaller 
        array[inner] = temp;//Now it will put the stored number into its ordered position. 
    }
} 

Answer 1

该行中 undefined variable array

for (int outer = 1; outer < array.length; outer++)//Outer=next number to be sorted 

如果这是一个函数参数，则像这样添加它

public static void insertionsort(int[] array) 
{
     for (int outer = 1; outer < array.length; outer++)//Outer=next number to be sorted 

或者在里面定义它

public static void insertionsort() 
{

    int[] array = {2,1,4,7,6,3};

    for (int outer = 1; outer < array.length; outer++)//Outer=next number to be sorted