Implement a quickerSort method

app/src/main/java/ch/nuth/zhaw/exbox/SortServer.java

@@ -16,7 +16,7 @@ public class SortServer implements CommandExecutor {
         a[j] = h;
     }
 
-    private void bubbleSort(int[] a) {
+    public void bubbleSort(int[] a) {
         for (int max = a.length - 1; max >= 0; max--) {
             boolean isSorted = true;
 
@@ -33,8 +33,12 @@ public class SortServer implements CommandExecutor {
         }
     }
 
-    private void insertionSort(int[] a) {
-        for (int k = 0; k < a.length; k++) {
+    public void insertionSort(int[] a) {
+        insertionSort(a, 0, a.length - 1);
+    }
+
+    private void insertionSort(int[] a, int min, int max) {
+        for (int k = min; k < max + 1; k++) {
             int item = a[k];
             int newIndex;
 
@@ -46,20 +50,7 @@ public class SortServer implements CommandExecutor {
         }
     }
 
-    private void insertionSort(int[] a, int l, int r) {
-        for (int k = l + 1; k < r + 1; k++) {
-            if (a[k] < a[k - 1]) {
-                int x = a[k];
-                int i;
-                for (i = k; ((i > 0) && (a[i - 1] > x)); i--) {
-                    a[i] = a[i - 1];
-                }
-                a[i] = x;
-            }
-        }
-    }
-
-    private void selectionSort(int[] a) {
+    public void selectionSort(int[] a) {
         // TODO Implement Aufgabe 3
         for (int i = 0; i < a.length; i++) {
             int minIndex = i;
@@ -88,11 +79,36 @@ public class SortServer implements CommandExecutor {
 
     private void quickerSort(int[] arr, int left, int right) {
         // To do Aufgabe 12.1
+        if (right - left < insertion_threshold) {
+            insertionSort(arr, left, right);
+        } else {
+            int l = partition(arr, left, right);
+            quickerSort(arr, left, l - 1);
+            quickerSort(arr, l, right);
+        }
     }
 
     private int partition (int[] arr, int left, int right) {
         // To do Aufgabe 12.1
-        return 0;
+        int pivot = arr[(left + right) / 2];
+
+        while (left <= right) {
+            while (arr[left] < pivot) {
+                left++;
+            }
+
+            while (arr[right] > pivot) {
+                right--;
+            }
+
+            if (left <= right) {
+                swap(arr, left, right);
+                left++;
+                right--;
+            }
+        }
+
+        return left;
     }
 
     private boolean isSorted(int[] a) {
@@ -140,7 +156,7 @@ public class SortServer implements CommandExecutor {
     // consumer sorts the data
     // return elapsed time in ms
     // if data is not sorted an exception is thrown
-    private double measureTime(Supplier<int[]> generator, Consumer<int[]> sorter) throws Exception {
+    public double measureTime(Supplier<int[]> generator, Consumer<int[]> sorter) throws Exception {
         double elapsed = 0;
 
         int[] a = generator.get();