triangle: fix access modifiers in example

exercises/triangle/src/example/java/Triangle.java

 import java.util.HashSet;
 import java.util.Set;
 
-public class Triangle {
+class Triangle {
 
     private double side1;
     private double side2;
     private double side3;
 
-    public Triangle(double side1, double side2, double side3) throws TriangleException {
+    Triangle(double side1, double side2, double side3) throws TriangleException {
         this.side1 = side1;
         this.side2 = side2;
         this.side3 = side3;
         }
     }
 
-    public TriangleKind getKind() {
+    TriangleKind getKind() {
         int uniqueSides = getNumberOfUniqueSides();
 
         if (uniqueSides == 1) {
         return side1 + side2 <= side3 || side1 + side3 <= side2 || side2 + side3 <= side1;
     }
 
-
-    public int getNumberOfUniqueSides() {
+    private int getNumberOfUniqueSides() {
         Set<Double> sides = new HashSet<>();
 
         sides.add(side1);
 
         return sides.size();
     }
+
 }