CODEWITHSUNDEEP
java
sohil
sohil

Reputation: 223

problems with static 1d arrays in 2d arrays

I am trying to create static array which i initialize later in the method

Something like this

static Object[][] table;
static Object[] codeZero;
static Object[] codeOne;

I call this method from main

static void init(){
    table = new Object[][]{codeZero,codeOne};
}

and then in another method i try something like this

codeZero=new Object[2];
codeOne=new Object[2];
table[0][0]= new Integer(4);

when i try to print table[0][0] it gives me a null pointer exception

Upvotes: 0

Views: 66

Answers (1)

Luiggi Mendoza
Luiggi Mendoza

Reputation: 85779

This is what's hapenning

  1. Instantiating table variable with null elements:

    table = new Object[][] { codeZero, codeOne };

  2. Change the references of codeZero and codeOne variables, the old references will still remain in table, they won't be replaced.

    codeZero = new Object[2];
codeOne = new Object[2];

  3. Since the old null references are still in table, you will get a NullPointerException when calling table[0][<whatever>].

Possible fix: Initialize codeZero and codeOne before initializing table. Then, initialize table using your currently approach:

    codeZero = new Object[2];
    codeOne = new Object[2];
    table = new Object[][] { codeZero, codeOne }

Upvotes: 3

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