Remove unnecessary code (#4141)

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

@@ -58,7 +58,7 @@ public class AmicableNumber {
             countofRes +
             " Amicable_numbers.These are \n "
         );
-        System.out.println(res.toString());
+        System.out.println(res);
     }
 
     /**

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

@@ -52,8 +52,7 @@ public class Combinations {
         // nC0 is always 1
         long solution = 1;
         for (int i = 0; i < k; i++) {
-            long next = (n - i) * solution / (i + 1);
-            solution = next;
+            solution = (n - i) * solution / (i + 1);
         }
         return solution;
     }

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

@@ -10,8 +10,7 @@ public class DistanceFormula {
     ) {
         double dX = Math.pow(x2 - x1, 2);
         double dY = Math.pow(y2 - x1, 2);
-        double d = Math.sqrt(dX + dY);
-        return d;
+        return Math.sqrt(dX + dY);
     }
 
     public static double manhattanDistance(
@@ -20,8 +19,7 @@ public class DistanceFormula {
         double x2,
         double y2
     ) {
-        double d = Math.abs(x1 - x2) + Math.abs(y1 - y2);
-        return d;
+        return Math.abs(x1 - x2) + Math.abs(y1 - y2);
     }
 
     public static int hammingDistance(int[] b1, int[] b2) {

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

@@ -26,22 +26,14 @@ public class EulerMethod {
         BiFunction<Double, Double, Double> exampleEquation1 = (x, y) -> x;
         ArrayList<double[]> points1 = eulerFull(0, 4, 0.1, 0, exampleEquation1);
         assert points1.get(points1.size() - 1)[1] == 7.800000000000003;
-        points1.forEach(point ->
-            System.out.println(
-                String.format("x: %1$f; y: %2$f", point[0], point[1])
-            )
-        );
+        points1.forEach(point -> System.out.printf("x: %1$f; y: %2$f%n", point[0], point[1]));
 
         // example from https://en.wikipedia.org/wiki/Euler_method
         System.out.println("\n\nexample 2:");
         BiFunction<Double, Double, Double> exampleEquation2 = (x, y) -> y;
         ArrayList<double[]> points2 = eulerFull(0, 4, 0.1, 1, exampleEquation2);
         assert points2.get(points2.size() - 1)[1] == 45.25925556817596;
-        points2.forEach(point ->
-            System.out.println(
-                String.format("x: %1$f; y: %2$f", point[0], point[1])
-            )
-        );
+        points2.forEach(point -> System.out.printf("x: %1$f; y: %2$f%n", point[0], point[1]));
 
         // example from https://www.geeksforgeeks.org/euler-method-solving-differential-equation/
         System.out.println("\n\nexample 3:");
@@ -55,11 +47,7 @@ public class EulerMethod {
             exampleEquation3
         );
         assert points3.get(points3.size() - 1)[1] == 1.1116729841674804;
-        points3.forEach(point ->
-            System.out.println(
-                String.format("x: %1$f; y: %2$f", point[0], point[1])
-            )
-        );
+        points3.forEach(point -> System.out.printf("x: %1$f; y: %2$f%n", point[0], point[1]));
     }
 
     /**
@@ -83,11 +71,7 @@ public class EulerMethod {
                 "stepSize should be greater than zero"
             );
         }
-        double yNext =
-            yCurrent +
-            stepSize *
-            differentialEquation.apply(xCurrent, yCurrent);
-        return yNext;
+        return yCurrent + stepSize * differentialEquation.apply(xCurrent, yCurrent);
     }
 
     /**

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

@@ -17,7 +17,7 @@ public class FastInverseSqrt {
         i = 0x5f3759df - (i >> 1);
         x = Float.intBitsToFloat(i);
         x = x * (1.5f - xhalf * x * x);
-        return x == (float) ((float) 1 / (float) Math.sqrt(number));
+        return x == ((float) 1 / (float) Math.sqrt(number));
     }
 
     /**

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

@@ -36,11 +36,7 @@ public class KrishnamurthyNumber {
             }
 
             //evaluating if sum of the factorials of the digits equals the number itself
-            if (tmp == s) {
-                return true;
-            } else {
-                return false;
-            }
+            return tmp == s;
         }
     }
 

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

@@ -3,7 +3,6 @@ package com.thealgorithms.maths;
 public class StandardScore {
 
     public static double zScore(double num, double mean, double stdDev) {
-        double z = (num - mean) / stdDev;
-        return z;
+        return (num - mean) / stdDev;
     }
 }