Created general interface for most algorithms

Created utils methods
Refactored ShellSort

Author: nikitap492

Sorts/ShellSort.java

@@ -1,68 +1,50 @@
 package Sorts;
 
+import static Sorts.SortUtils.*;
+
+
 /**
  * @author dpunosevac
+ * @author Podshivalov Nikita (https://github.com/nikitap492)
+ *
+ * @see SortAlgorithm
+ *
  */
-public class ShellSort {
+public class ShellSort implements SortAlgorithm {
 
   /**
    * This method implements Generic Shell Sort.
    * @param array The array to be sorted
    */
-  public static void shellSort(Comparable[] array) {
+  @Override
+  public <T extends Comparable<T>> T[] sort(T[] array) {
     int N = array.length;
     int h = 1;
 
     while (h < N/3) {
-      h = 3 * h + 1;
+        h = 3 * h + 1;
     }
 
     while (h >= 1) {
-      for (int i = h; i < N; i++) {
-        for (int j = i; j >= h && less(array[j], array[j-h]); j -= h) {
-          exch(array, j, j - h);
+        for (int i = h; i < N; i++) {
+            for (int j = i; j >= h && less(array[j], array[j-h]); j -= h) {
+                swap(array, j, j - h);
+            }
         }
-      }
 
-      h /= 3;
+        h /= 3;
     }
-  }
 
-  /**
-   * Helper method for exchanging places in array
-   * @param array The array which elements we want to swap
-   * @param i index of the first element
-   * @param j index of the second element
-   */
-  private static void exch(Comparable[] array, int i, int j) {
-    Comparable swap = array[i];
-    array[i] = array[j];
-    array[j] = swap;
-  }
-
-  /**
-   * This method checks if first element is less then the other element
-   * @param v first element
-   * @param w second element
-   * @return true if the first element is less then the second element
-   */
-  private static boolean less(Comparable v, Comparable w) {
-    return v.compareTo(w) < 0;
+    return array;
   }
 
   public static void main(String[] args) {
-    // Integer Input
-    int[] arr1 = {4,23,6,78,1,54,231,9,12};
-    Integer[] array = new Integer[arr1.length];
+      Integer[] toSort = {4, 23, 6, 78, 1, 54, 231, 9, 12};
 
-    for (int i=0;i<arr1.length;i++) {
-      array[i] = arr1[i];
-    }
+      ShellSort sort = new ShellSort();
+      Integer[] sorted = sort.sort(toSort);
 
-    shellSort(array);
+      print(sorted);
 
-    for (int i = 0; i < array.length; i++) {
-      System.out.println(array[i]);
-    }
   }
 }

Sorts/SortAlgorithm.java

@@ -0,0 +1,13 @@
+package Sorts;
+
+/**
+ *  The common interface of most algorithms
+ *
+ * @author Podshivalov Nikita (https://github.com/nikitap492)
+ *
+ **/
+public interface SortAlgorithm {
+
+    <T extends Comparable<T>> T[] sort(T[] unsorted);
+
+}

Sorts/SortUtils.java

@@ -0,0 +1,60 @@
+package Sorts;
+
+import java.util.Arrays;
+import java.util.List;
+
+/**
+ * The class contains util methods
+ *
+ * @author Podshivalov Nikita (https://github.com/nikitap492)
+ *
+ **/
+final class SortUtils {
+
+
+    /**
+     * Helper method for swapping places in array
+     * @param array The array which elements we want to swap
+     * @param idx index of the first element
+     * @param idy index of the second element
+     */
+    static <T> void swap(T[] array, int idx, int idy){
+        T swap = array[idx];
+        array[idx] = array[idy];
+        array[idy] = swap;
+    }
+
+
+    /**
+     * This method checks if first element is less then the other element
+     * @param v first element
+     * @param w second element
+     * @return true if the first element is less then the second element
+     */
+    static <T extends Comparable<T>> boolean less(T v, T w) {
+        return v.compareTo(w) < 0;
+    }
+
+
+    /**
+     * Just print list
+     * @param toPrint - a list which should be printed
+     */
+    static void print(List<?> toPrint){
+        toPrint.stream()
+                .map(Object::toString)
+                .map(str -> str + " ")
+                .forEach(System.out::print);
+
+        System.out.println();
+    }
+
+
+    /**
+     * Prints an array
+     * @param toPrint - the array  which should be printed
+     */
+    static void print(Object[] toPrint){
+       print(Arrays.asList(toPrint));
+    }
+}