add examples in java 8 (#12)

* code for chapters 3-9 in Java

* code for chapters 1 in Java

* code for chapter 2 in Java

* missing CheckVoter for chapter 5 in Java

* add missing sample output for SetCovering as a comment

02_selection_sort/java/src/SelectionSort.java

@@ -0,0 +1,37 @@
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+public class SelectionSort {
+
+    private static List<Integer> selectionSort(List<Integer> arr) {
+        List<Integer> newArr = new ArrayList<>(arr.size());
+
+        int size = arr.size();
+        for (int i = 0; i < size; i++) {
+            int smallest = findSmallest(arr);
+            newArr.add(arr.get(smallest));
+
+            arr.remove(smallest);
+        }
+
+        return newArr;
+    }
+
+    private static int findSmallest(List<Integer> arr) {
+        int smallest = arr.get(0);
+        int smallestIndex = 0;
+        for (int i = 0; i < arr.size(); i++) {
+            if (arr.get(i) < smallest) {
+                smallest = arr.get(i);
+                smallestIndex = i;
+            }
+        }
+        return smallestIndex;
+    }
+
+    public static void main(String[] args) {
+        List<Integer> arr = new ArrayList<>(Arrays.asList(5, 3, 6, 2, 10));
+        System.out.println(selectionSort(arr)); //[2, 3, 5, 6, 10]
+    }
+}

02_selection_sort/java/src/SelectionSort2.java

@@ -0,0 +1,33 @@
+import java.util.Arrays;
+
+public class SelectionSort2 {
+
+    // this version uses raw arrays instead of ArrayList
+    private static int[] selectionSort(int[] arr) {
+        int[] newArr = new int[]{arr.length};
+
+        for (int i = 0; i < newArr.length; i++) {
+            int smallest = findSmallest(arr, i);
+            newArr[i] = arr[smallest];
+        }
+
+        return newArr;
+    }
+
+    private static int findSmallest(int[] arr, int low) {
+        int smallest = arr[low];
+        int smallestIndex = low;
+        for (int i = low + 1; i < arr.length; i++) {
+            if (arr[i] < smallest) {
+                smallest = arr[i];
+                smallestIndex = i;
+            }
+        }
+        return smallestIndex;
+    }
+
+    public static void main(String[] args) {
+        int[] arr = {5, 3, 6, 2, 10};
+        System.out.println(Arrays.toString(selectionSort(arr))); // [2, 3, 5, 6, 10]
+    }
+}