Issues with making string accessable to rest of program - processing

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";
}
}