Tidy up binary search hints and reference implementation

exercises/binary-search/.meta/hints.md

 
 For example you could construct a list of `Integers`:
 
-`List<Integer> someList = new LinkedList();`
+`List<Integer> someList = new LinkedList<>();`
 
 Now `someList` can only contain `Integers`. You could also do:
 
-`List<String> someOtherList = new LinkedList()`
+`List<String> someOtherList = new LinkedList<>()`
 
 Now `someOtherList` can only contain `Strings`.
 
 Another constraint is that any type used with generics cannot be a [primitive type](https://docs.oracle.com/javase/tutorial/java/nutsandbolts/datatypes.html), such as `int` or `long`.
+However, every primitive type has a corresponding reference type, so instead of `int` you can use [`Integer`](https://docs.oracle.com/javase/8/docs/api/java/lang/Integer.html) and instead of `long` you can use [`Long`](https://docs.oracle.com/javase/8/docs/api/java/lang/Long.html).
 
 It can help to look at an [example use case of generics](https://docs.oracle.com/javase/tutorial/java/generics/types.html) to get you started.

exercises/binary-search/.meta/src/reference/java/BinarySearch.java

 
 import java.util.List;
 
-public class BinarySearch<T extends Comparable<T>> {
+class BinarySearch<T extends Comparable<T>> {
 
     private List<T> array;
     private int arraySize;
 
-    public BinarySearch(List<T> array) {
+    BinarySearch(List<T> array) {
         this.array = array;
         this.arraySize = array.size();
     }
 
-    public int indexOf(T value) {
+    int indexOf(T value) {
         return search(value);
     }
 
-    public List<T> getArray() {
-        return array;
-    }
-
     private int search(T value) {
         int left = 0;
         int right = this.arraySize - 1;