style: enable MultipleVariableDeclarations in checkstyle (#5175)

Co-authored-by: vaibhav <vaibhav.waghmare@techprescient.com>

src/main/java/com/thealgorithms/maths/AutomorphicNumber.java

@@ -24,7 +24,8 @@ public final class AutomorphicNumber {
     public static boolean isAutomorphic(long n) {
         if (n < 0) return false;
         long square = n * n; // Calculating square of the number
-        long t = n, numberOfdigits = 0;
+        long t = n;
+        long numberOfdigits = 0;
         while (t > 0) {
             numberOfdigits++; // Calculating number of digits in n
             t /= 10;

src/main/java/com/thealgorithms/maths/DeterminantOfMatrix.java

@@ -13,7 +13,10 @@ public final class DeterminantOfMatrix {
     // Determinant calculator
     //@return determinant of the input matrix
     static int determinant(int[][] a, int n) {
-        int det = 0, sign = 1, p = 0, q = 0;
+        int det = 0;
+        int sign = 1;
+        int p = 0;
+        int q = 0;
         if (n == 1) {
             det = a[0][0];
         } else {

src/main/java/com/thealgorithms/maths/FFT.java

@@ -24,7 +24,8 @@ public final class FFT {
      */
     static class Complex {
 
-        private double real, img;
+        private double real;
+        private double img;
 
         /**
          * Default Constructor. Creates the complex number 0.

src/main/java/com/thealgorithms/maths/FindKthNumber.java

@@ -41,7 +41,8 @@ public final class FindKthNumber {
     }
 
     private static int findKthMax(int[] nums, int k) {
-        int start = 0, end = nums.length;
+        int start = 0;
+        int end = nums.length;
         while (start < end) {
             int pivot = partition(nums, start, end);
             if (k == pivot) {

src/main/java/com/thealgorithms/maths/Gaussian.java

@@ -8,7 +8,8 @@ public final class Gaussian {
 
     public static ArrayList<Double> gaussian(int mat_size, ArrayList<Double> matrix) {
         ArrayList<Double> answerArray = new ArrayList<Double>();
-        int i, j = 0;
+        int i;
+        int j = 0;
 
         double[][] mat = new double[mat_size + 1][mat_size + 1];
         double[][] x = new double[mat_size][mat_size + 1];
@@ -43,7 +44,8 @@ public final class Gaussian {
     // calculate the x_1, x_2, ... values of the gaussian and save it in an arraylist.
     public static ArrayList<Double> valueOfGaussian(int mat_size, double[][] x, double[][] mat) {
         ArrayList<Double> answerArray = new ArrayList<Double>();
-        int i, j;
+        int i;
+        int j;
 
         for (i = 0; i < mat_size; i++) {
             for (j = 0; j <= mat_size; j++) {

src/main/java/com/thealgorithms/maths/KeithNumber.java

@@ -11,9 +11,10 @@ final class KeithNumber {
     // user-defined function that checks if the given number is Keith or not
     static boolean isKeith(int x) {
         // List stores all the digits of the X
-        ArrayList<Integer> terms = new ArrayList<Integer>();
+        ArrayList<Integer> terms = new ArrayList<>();
         // n denotes the number of digits
-        int temp = x, n = 0;
+        int temp = x;
+        int n = 0;
         // executes until the condition becomes false
         while (temp > 0) {
             // determines the last digit of the number and add it to the List
@@ -25,7 +26,8 @@ final class KeithNumber {
         }
         // reverse the List
         Collections.reverse(terms);
-        int next_term = 0, i = n;
+        int next_term = 0;
+        int i = n;
         // finds next term for the series
         // loop executes until the condition returns true
         while (next_term < x) {

src/main/java/com/thealgorithms/maths/LeastCommonMultiple.java

@@ -30,7 +30,8 @@ public final class LeastCommonMultiple {
      * get least common multiple from two number
      */
     public static int lcm(int num1, int num2) {
-        int high, num3;
+        int high;
+        int num3;
         int cmv = 0;
         /*
          * value selection for the numerator

src/main/java/com/thealgorithms/maths/NonRepeatingElement.java

@@ -13,7 +13,8 @@ public final class NonRepeatingElement {
 
     public static void main(String[] args) {
         try (Scanner sc = new Scanner(System.in)) {
-            int i, res = 0;
+            int i;
+            int res = 0;
             System.out.println("Enter the number of elements in the array");
             int n = sc.nextInt();
             if ((n & 1) == 1) {
@@ -42,7 +43,8 @@ public final class NonRepeatingElement {
 
             // Finding the rightmost set bit
             res = res & (-res);
-            int num1 = 0, num2 = 0;
+            int num1 = 0;
+            int num2 = 0;
 
             for (i = 0; i < n; i++) {
                 if ((res & arr[i]) > 0) { // Case 1 explained below

src/main/java/com/thealgorithms/maths/PollardRho.java

@@ -59,7 +59,9 @@ public final class PollardRho {
      * @throws RuntimeException object if GCD of given number cannot be found
      */
     static int pollardRho(int number) {
-        int x = 2, y = 2, d = 1;
+        int x = 2;
+        int y = 2;
+        int d = 1;
         while (d == 1) {
             // tortoise move
             x = g(x, number);

src/main/java/com/thealgorithms/maths/PrimeCheck.java

@@ -56,7 +56,8 @@ public final class PrimeCheck {
      */
     public static boolean fermatPrimeChecking(int n, int iteration) {
         long a;
-        int up = n - 2, down = 2;
+        int up = n - 2;
+        int down = 2;
         for (int i = 0; i < iteration; i++) {
             a = (long) Math.floor(Math.random() * (up - down + 1) + down);
             if (modPow(a, n - 1, n) != 1) {