Null pointer Exception in Java when assigning value to int array

Question

My code shows null pointer exception when i assign values to int array in the object:

public class Cage {
    int Value;  
    String Operator;
    int[] placeHolders;
}

Cage o = new Cage();                
o.Value = Integer.parseInt(strSplit[0]);
o.Operator = strSplit[1];               
for(int i=2;i<strSplit.length;i++) {
    o.placeHolders[i] = Integer.parseInt(strSplit[i]);
}

Answer 1

您应该为placeHolders创建一个int数组，它只是一个声明，而不是现在的定义。

o.placeHolders = new int[strSplit.length];

Answer 2

I guess that you want to have placeHolders to hold values without null values in the first to indexes.

o.placeHolders = new int[strSplit.length - 2];
for (int i = 0; i < strSplit.length - 2; i++) {
    o.placeHolders[i] = Integer.parseInt(strSplit[i + 2]);
}

Answer 3

您应该在使用它之前实例化int []对象：

int[] placeHolders = new int[100];