add files for refactoring task

src/main/java/refactoring/Article.java

@@ -0,0 +1,12 @@
+package refactoring;
+
+public class Article {
+
+    public Bike bike;
+    public int purchaseAmount;
+
+    public Article(Bike b, int pa) {
+        bike = b;
+        purchaseAmount = pa;
+    }
+}

src/main/java/refactoring/Bike.java

@@ -0,0 +1,16 @@
+package refactoring;
+
+public class Bike {
+
+    public String productName;
+    public double price;
+    public Integer batteryCapacity;
+
+    public Integer getBatteryCapacity() {
+        return batteryCapacity;
+    }
+
+    public int getGearsCount() {
+        throw new UnsupportedOperationException("Not Implemented");
+    }
+}

src/main/java/refactoring/Bill.java

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+package refactoring;
+
+import java.util.ArrayList;
+import java.util.Date;
+
+public class Bill {
+
+    public String customerName;
+    public String nickname;
+    public Date birthday;
+    public String email;
+    public String street;
+    public String streetNumber;
+    public int postalCode;
+    public String city;
+    public ArrayList<Article> articles;
+
+    public Bill(String cn, String n, String s, String sn, int pc, Date b, String e, String c) {
+        customerName = cn;
+        nickname = n;
+        street = s;
+        streetNumber = sn;
+        postalCode = pc;
+        birthday = b;
+        email = e;
+        city = c;
+        articles = new ArrayList<Article>();
+    }
+
+    public boolean addArticle(Article a) {
+        return articles.add(a);
+    }
+
+    public String getDetails() {
+        double total = 0;
+
+        String result = "Details for \"" + customerName + "\"\n";
+        result += street + " " + streetNumber + "\n";
+        result += postalCode + " " + city + "\n";
+        result += "Geburtstag: " + birthday + "\n";
+        result += "Email: " + email + "\n\n";
+        result += "refactoring.Article: \n";
+        for (Article article : articles) {
+            double price = 0;
+            if (article.bike instanceof Brompton) {
+                if (article.purchaseAmount > 1) {
+                    price += (article.purchaseAmount - 1) * article.bike.price / 2;
+                }
+                price += article.bike.price * article.purchaseAmount;
+            } else if (article.bike instanceof EBike) {
+                price += article.bike.price * article.purchaseAmount;
+            } else if (article.bike instanceof Mountainbike) {
+                if (article.purchaseAmount > 2) {
+                    price += article.purchaseAmount * article.bike.price * 9 / 10;
+                } else {
+                    price += article.bike.price * article.purchaseAmount;
+                }
+            }
+            if (price > 1000f || price == 1000.0) {
+                price = price * 0.8;
+            }
+
+            result +=
+                    "\t"
+                            + article.bike.productName
+                            + "\tx\t"
+                            + article.purchaseAmount
+                            + "\t=\t"
+                            + String.valueOf(price)
+                            + "\n";
+            total += price;
+        }
+
+        result += "\nTotal price:\t" + String.valueOf(total) + "\n";
+
+        return result;
+    }
+}

src/main/java/refactoring/Brompton.java

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+package refactoring;
+
+public class Brompton extends Bike {
+
+    public int maxSpeed;
+    public int rearGearsCount;
+    public int frontGearsCount;
+
+    public Brompton(String pn, double p, int ms, int rgc, int fgc) {
+        productName = pn;
+        price = p;
+        maxSpeed = ms;
+        rearGearsCount = rgc;
+        frontGearsCount = fgc;
+    }
+
+    public int getMaxSpeed() {
+        return maxSpeed;
+    }
+
+    @Override
+    public Integer getBatteryCapacity() {
+        return null;
+    }
+
+    @Override
+    public int getGearsCount() {
+        return rearGearsCount * frontGearsCount;
+    }
+}

src/main/java/refactoring/EBike.java

@@ -0,0 +1,26 @@
+package refactoring;
+
+public class EBike extends Bike {
+
+    public int maxSpeed;
+    public int rearGearsCount;
+    public int frontGearsCount;
+
+    public EBike(String pn, double p, int ms, int rgc, int fgc, int bc) {
+        productName = pn;
+        price = p;
+        maxSpeed = ms;
+        rearGearsCount = rgc;
+        frontGearsCount = fgc;
+        batteryCapacity = bc;
+    }
+
+    public int getMaxSpeed() {
+        return maxSpeed;
+    }
+
+    @Override
+    public int getGearsCount() {
+        return rearGearsCount * frontGearsCount;
+    }
+}

src/main/java/refactoring/Mountainbike.java

@@ -0,0 +1,30 @@
+package refactoring;
+
+public class Mountainbike extends Bike {
+
+    public int maxSpeed;
+    public int rearGearsCount;
+    public int frontGearsCount;
+
+    public Mountainbike(String pn, double p, int ms, int rgc, int fgc) {
+        productName = pn;
+        price = p;
+        maxSpeed = ms;
+        rearGearsCount = rgc;
+        frontGearsCount = fgc;
+    }
+
+    public int getMaxSpeed() {
+        return maxSpeed;
+    }
+
+    @Override
+    public Integer getBatteryCapacity() {
+        return null;
+    }
+
+    @Override
+    public int getGearsCount() {
+        return rearGearsCount * frontGearsCount;
+    }
+}