Netbeans is suggesting to convert a field to a final despite the fact that I modify this field

Question

First, here is the relevant code:

public class AtCounter
{
    private char[][] atMat;
    private int atCount;

    public AtCounter()
    {
        atCount=0;
        atMat= new char[][]{{'@','-','@','-','-','@','-','@','@','@'},
                            {'@','@','@','-','@','@','-','@','-','@'}, 
                            {'-','-','-','-','-','-','-','@','@','@'}, 
                            {'-','@','@','@','@','@','-','@','-','@'}, 
                            {'-','@','-','@','-','@','-','@','-','@'}, 
                            {'@','@','@','@','@','@','-','@','@','@'}, 
                            {'-','@','-','@','-','@','-','-','-','@'}, 
                            {'-','@','@','@','-','@','-','-','-','-'}, 
                            {'-','@','-','@','-','@','-','@','@','@'}, 
                            {'-','@','@','@','@','@','-','@','@','@'}};

    }

    public int countAts(int r, int c)
    {

        if(r<atMat.length && c<atMat[0].length && r>=0 && c>=0 && atMat[r][c]=='@')
        {
            atMat[r][c]='X';
            atCount++;
        }
        else
            if(r-1<atMat.length && r-1>=0)
                countAts(r-1,c);
        else
                if(r+1<atMat.length && r+1>=0)
                    countAts(r+1,c);
        else
                    if(c-1<atMat[0].length && c-1>=0)
                        countAts(r,c-1);
        else
                        if(c+1<atMat[0].length && c+1>=0)
                            countAts(r,c+1);
        return atCount;

    }

Note that the countsAts method contains the line atMat[r][c]='X';, which changes the value of an element within the two-dimensional array. Despite this fact, on the line private char[][] atMat;, Netbeans gives me the warning "Field atMat can be final". Why would this field be able to be final if I am modifying its value? Does it have something to do with where in the code I am currently modifying it? Is Netbeans bugged (doubt it)? If someone could explain the warning I would be very grateful!

Answer 1

You can change the contents of the object that is referenced by the name atMat. atMat is a reference. The reference itself can be made final.