Nullpointer Exception in function with 2d array as argument

Question

I excepted that my functions in Level.java class allow me to make 2D array copy at any time in my program then change size of level array and fill it with values of copy and at last display it.

When I try to run my program it shows NullPointerException at line 24 in Level.java (a part which replaces the values).

Game.java Class

package main;

public class Game {

public static void main(String[] args) {
    Level lvl = new Level();
        char[][] exampleLevelTemplate = new char[][] {
            {'#','#','#'},
            {'#','#','#'},
            {'#','#','#'}
        };
        lvl.setLevelSize(3,3);
        lvl.setLevelLayout(exampleLevelTemplate);
        lvl.displayLevel();     
    }

}

Level.java Class

package main;

public class Level {

private int levelWidth;
private int levelHight;
private char[][]level;

public void setLevelSize(int Width,int Height)
{
    levelWidth = Width;
    levelHight = Height;
    char[][]level = new char[levelWidth][levelHight];
}

public void setLevelLayout(char[][]levelTemplate)
{
    int a; 
    int b;
    for(a=0; a < levelWidth; a++)
    {
        for(b=0; b<levelHight; b++)
        {
            level[a][b] = levelTemplate[a][b]; //Error happens here
        }
    }       
}

public void displayLevel()
{
    int a; 
    int b;
    for(a=0; a < levelWidth; a++)
    {
        for(b=0; b<levelHight; b++)
        {
            System.out.println(level[a][b]);
        }
    }
}

}

whatamidoingwithmylife · Accepted Answer · 2017-12-02 19:11:37Z

1

Change your setLevelSize method to this:

public void setLevelSize(int Width,int Height)
{
    levelWidth = Width;
    levelHight = Height;
    level = new char[levelWidth][levelHight];
}

You will see that line:

char[][]level = new char[levelWidth][levelHight];

was changed to:

level = new char[levelWidth][levelHight];

You need to just assign the array Object to array reference variable "level" and not create a local one and initialize it like you did.

You have been assigning value to a null array reference variable and therefore got NullPointerException.

answered Dec 2, 2017 at 19:11

whatamidoingwithmylife

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