unexpected results: null next to the string

import java.util.*;
public class Main {
public static void main(String[] args) {
Scanner scan1 = new Scanner(System.in);
int test = scan1.nextInt();
String[] sArr = new String[test];
sArr[0] = "";
// String s = "";
//  StringBuilder sB = new StringBuilder(s);
int y = 0;
while (test > 0) {
char c;
test--;
Scanner scan2 = new Scanner(System.in);
Scanner scan3 = new Scanner(System.in);
int n = scan2.nextInt();
String str = scan3.nextLine();
String[] nSplit = str.split("(?<=\\G.)");
int[] x = new int[n];
for (int i = 0; i < n * 4 - 3; i += 4) {
nSplit[i] += nSplit[i + 2];
nSplit[i + 1] += nSplit[i + 3];
}
for (int i = 0, j = 0; i < x.length; i++, j += 4) {
x[i] = Integer.parseInt(nSplit[j]) + Integer.parseInt(nSplit[j + 1]);
c = (char) x[i];
sArr[test] += c;
}
}
for (int i = sArr.length-1; i >-1; i--) {
System.out.println(sArr[i]);
}
}
}

input:

5

1

1234

1

2345

1

3456

1

4567

1

5678

output:

null%

null;

nullQ

nullg

}
//end

where did these null come from? how to get rid of it?
why is there not null next to the last element?

if null means a blank at the selected array index then what it means in this case?

Basically what is happening is you are creating an array of Strings.
And you are only initialising the first element of the array to ""
sArr[0] = "";

That is why every other element but the first element has a null preceding it.

So this statement sArr[test] += c; is going to add a null value for all non initialised strings in your array of Strings.

I would suggest instead of sArr[0] = ""; you can do this
Arrays.fill(sArr , "")
It initialises all values of the strings in the array to ""

Arrays is a class found under utils which you are importing.