refactoring : divergent change - move function

refactoring/src/main/java/com/example/refactoring/_07_divergent_change/_25_move_function/Account.java

@@ -0,0 +1,25 @@
+package com.example.refactoring._07_divergent_change._25_move_function;
+
+public class Account {
+
+    private int daysOverdrawn;
+
+    private AccountType type;
+
+    public Account(int daysOverdrawn, AccountType type) {
+        this.daysOverdrawn = daysOverdrawn;
+        this.type = type;
+    }
+
+    public double getBankCharge() {
+        double result = 4.5;
+        if (this.daysOverdrawn() > 0) {
+            result += this.type.overdraftCharge(this.daysOverdrawn());
+        }
+        return result;
+    }
+
+    private int daysOverdrawn() {
+        return this.daysOverdrawn;
+    }
+}

refactoring/src/main/java/com/example/refactoring/_07_divergent_change/_25_move_function/AccountType.java

@@ -0,0 +1,26 @@
+package com.example.refactoring._07_divergent_change._25_move_function;
+
+public class AccountType {
+    private boolean premium;
+
+    public AccountType(boolean premium) {
+        this.premium = premium;
+    }
+
+    public boolean isPremium() {
+        return this.premium;
+    }
+
+    public double overdraftCharge(int daysOverdrawn) {
+        if (this.isPremium()) {
+            final int baseCharge = 10;
+            if (daysOverdrawn <= 7) {
+                return baseCharge;
+            } else {
+                return baseCharge + (daysOverdrawn - 7) * 0.85;
+            }
+        } else {
+            return daysOverdrawn * 1.75;
+        }
+    }
+}

refactoring/src/main/java/com/example/refactoring/_07_divergent_change/_25_move_function/_before/Account.java

@@ -0,0 +1,38 @@
+package com.example.refactoring._07_divergent_change._25_move_function._before;
+
+public class Account {
+
+    private int daysOverdrawn;
+
+    private AccountType type;
+
+    public Account(int daysOverdrawn, AccountType type) {
+        this.daysOverdrawn = daysOverdrawn;
+        this.type = type;
+    }
+
+    public double getBankCharge() {
+        double result = 4.5;
+        if (this.daysOverdrawn() > 0) {
+            result += this.overdraftCharge();
+        }
+        return result;
+    }
+
+    private int daysOverdrawn() {
+        return this.daysOverdrawn;
+    }
+
+    private double overdraftCharge() {
+        if (this.type.isPremium()) {
+            final int baseCharge = 10;
+            if (this.daysOverdrawn <= 7) {
+                return baseCharge;
+            } else {
+                return baseCharge + (this.daysOverdrawn - 7) * 0.85;
+            }
+        } else {
+            return this.daysOverdrawn * 1.75;
+        }
+    }
+}

refactoring/src/main/java/com/example/refactoring/_07_divergent_change/_25_move_function/_before/AccountType.java

@@ -0,0 +1,13 @@
+package com.example.refactoring._07_divergent_change._25_move_function._before;
+
+public class AccountType {
+    private boolean premium;
+
+    public AccountType(boolean premium) {
+        this.premium = premium;
+    }
+
+    public boolean isPremium() {
+        return this.premium;
+    }
+}

refactoring/src/test/java/com/example/refactoring/_07_divergent_change/_25_move_function/AccountTest.java

@@ -0,0 +1,21 @@
+package com.example.refactoring._07_divergent_change._25_move_function;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class AccountTest {
+
+    @Test
+    void bankCharge() {
+        Account account = new Account(5, new AccountType(true));
+        assertEquals(14.5, account.getBankCharge());
+
+        account = new Account(8, new AccountType(true));
+        assertEquals(15.35, account.getBankCharge());
+
+        account = new Account(8, new AccountType(false));
+        assertEquals(18.5, account.getBankCharge());
+    }
+
+}