Issues with making string accessable to rest of program

Question

String[] input;
String output;

void setup() {

    selectInput("Select a file to process:", "fileSelected")
    println("########");
}

void draw() {

    println(output);
}

void fileSelected(File selection) {

    if(selection == null) {
        println("Window was closed or the user hit 'cancel.'");
    } else {
        String filepath=selection.getAbsolutePath();
        input=loadStrings(filepath);
        println(input);
        input.equals(output);
        println(output);
    }
}

I am working on a game project that needs to have a large matrix of integers loaded into a 2D array. I am using processing 3.4 and was using the selectInput() method as shown in the reference and loading the contents of a file into a string using loadStrings() like so.

I couldn't get this code to run because if I try to print the contents of 'input' I get the hated 'null pointer exception'. I don't know why this is, especially because the variable is a global variable. So I stated to use the 'output' variable to get around the null pointer issue. I print the output of input[] and output so that I can see that they have loaded, and I put the println(output); in draw() to see if I can access it. All I get is “null” (without quotes) printed to my console.

It appears that the output string is always empty. Even when I mades sure that is was declared as a “global level” variable, the variable is still null. I need the variable to be accessible on a public/global level so that the rest of the game code can convert the string into a matrix ( which I didn’t include here because it isn't important).

How can I load this string so that the rest of my code can use it?

Answer 1

The output string is always empty because you are not copying the input into it, the method equals doesn't work like that. I fixed your code and it works fine

String[] input;
String output;

void setup() {
    selectInput("Select a file to process:", "fileSelected");
    println("########");
}

void draw() {
    if(output!=null)
    println(output);
}

void fileSelected(File selection) {

    if(selection == null) 
    {
        println("Window was closed or the user hit 'cancel.'");
    } 
    else {
        String filepath=selection.getAbsolutePath();
        input=loadStrings(filepath);

        for(int i=0;i<input.length;i++)
        output+=input[i]+"\n";       
    }
}