LLD-2 HW Sai

.gitignore

@@ -0,0 +1,2 @@
+./.idea/*
+./.idea

LowLevelDesignConcepts.iml

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<module type="JAVA_MODULE" version="4">
+  <component name="NewModuleRootManager">
+    <output url="file://$MODULE_DIR$/bin" />
+    <exclude-output />
+    <content url="file://$MODULE_DIR$">
+      <sourceFolder url="file://$MODULE_DIR$/src" isTestSource="false" />
+    </content>
+    <orderEntry type="inheritedJdk" />
+    <orderEntry type="sourceFolder" forTests="false" />
+  </component>
+</module>

src/oops/SOLID/lsp/stack/before/IStack.java

@@ -0,0 +1,8 @@
+package oops.SOLID.lsp.stack.before;
+
+public interface IStack<T> {
+     void push(T i);
+     void pop();
+     T top();
+     void clear();
+}

src/oops/SOLID/lsp/stack/before/StackWrong.java

@@ -1,42 +1,51 @@
 package oops.SOLID.lsp.stack.before;
 
 import java.util.ArrayList;
+import java.util.List;
+
 /*
  * Stack is-a list with push() pop() methods.
  * So can we create a stack by extending an ArrayList class?
- * 
+ *
  * No! This implementation violates the Liskov Substitution Principle.
- * Which states that 
+ * Which states that
  * "Objects in a program should be replaceable with instances of their subtypes
  * without altering the correctness of that program."
- * 
+ *
  * In this case ArrayList has multiple methods which stack is not supposed to have (ex clear(), get(i) etc)
- * so objects of ArrayList are not fully replaceable by the objects of stack.   
- * 
+ * so objects of ArrayList are not fully replaceable by the objects of stack.
+ *
  */
-public class StackWrong extends ArrayList<Integer>{
-	private int topPointer = 0;
-
-	public void push(Integer a) {
-		add(topPointer, a);
-		topPointer++;
-	}	
-	public void pop() {
-		remove(topPointer-1);
-		topPointer--;
-	}
-	public Integer top() {
-		return get(topPointer-1);
-	}
-
-	public static void main(String[] args) {
-		StackWrong st = new StackWrong();
-		st.push(1);
-		st.push(2);
-		System.out.println(st.top());
-		st.pop();
-		System.out.println(st.top());
-		st.clear();
-		System.out.println(st.top());
-	}
+public class StackWrong implements IStack<Integer> {
+    private int topPointer = 0;
+    private List<Integer> list = new ArrayList<>();
+
+    public void push(Integer a) {
+        list.add(topPointer, a);
+        topPointer++;
+    }
+
+    public void pop() {
+        list.remove(topPointer - 1);
+        topPointer--;
+    }
+
+    public Integer top() {
+        return list.get(topPointer - 1);
+    }
+
+    public void clear() {
+        list.clear();
+    }
+
+    public static void main(String[] args) {
+        IStack<Integer> st = new StackWrong();
+        st.push(1);
+        st.push(2);
+        System.out.println(st.top());
+        st.pop();
+        System.out.println(st.top());
+        st.clear();
+        System.out.println(st.top());
+    }
 }

src/oops/SOLID/openClosePrinciple/before/client/CalculateTaxesClient.java

@@ -26,10 +26,10 @@ public static void main(String[] args) {
         for (Employee employee: employees){
 
             // compute individual tax
-            double tax = TaxCalculator.calculate(employee);
+            double tax = employee.calculateTax();
             String formattedTax = currencyFormatter.format(tax);
             // add to company total taxes
-            totalTaxes += TaxCalculator.calculate(employee);
+            totalTaxes += employee.calculateTax();
         }
     }
 }

src/oops/SOLID/openClosePrinciple/before/employees/Employee.java

@@ -57,5 +57,7 @@ public void setNbHoursPerWeek(int nbHoursPerWeek) {
     public String getFullName(){
         return this.firstName + " " + this.lastName;
     }
+
+    public abstract double calculateTax();
 }
 

src/oops/SOLID/openClosePrinciple/before/employees/FullTimeEmployee.java

@@ -1,8 +1,17 @@
 package oops.SOLID.openClosePrinciple.before.employees;
 
+import oops.SOLID.openClosePrinciple.before.taxes.FullTimeEmployeeTaxCalculator;
+import oops.SOLID.openClosePrinciple.before.taxes.TaxCalculator;
+
 public class FullTimeEmployee extends Employee {
     public FullTimeEmployee(String fullName, int monthlyIncome) {
         super(fullName, monthlyIncome);
         this.setNbHoursPerWeek(40);
     }
+
+    @Override
+    public double calculateTax() {
+        TaxCalculator<FullTimeEmployee> taxCalculator = new FullTimeEmployeeTaxCalculator();
+        return taxCalculator.calculate(this);
+    }
 }

src/oops/SOLID/openClosePrinciple/before/employees/Intern.java

@@ -1,8 +1,17 @@
 package oops.SOLID.openClosePrinciple.before.employees;
 
+import oops.SOLID.openClosePrinciple.before.taxes.InternTaxCalculator;
+import oops.SOLID.openClosePrinciple.before.taxes.TaxCalculator;
+
 public class Intern extends Employee {
     public Intern(String fullName, int monthlyIncome, int nbHours) {
         super(fullName, monthlyIncome);
         setNbHoursPerWeek(nbHours);
     }
+
+    @Override
+    public double calculateTax() {
+        TaxCalculator<Intern> taxCalculator = new InternTaxCalculator();
+        return taxCalculator.calculate(this);
+    }
 }

src/oops/SOLID/openClosePrinciple/before/employees/PartTimeEmployee.java

@@ -1,8 +1,17 @@
 package oops.SOLID.openClosePrinciple.before.employees;
 
+import oops.SOLID.openClosePrinciple.before.taxes.PartTimeEmployeeTaxCalculator;
+import oops.SOLID.openClosePrinciple.before.taxes.TaxCalculator;
+
 public class PartTimeEmployee extends Employee {
     public PartTimeEmployee(String fullName, int monthlyIncome) {
         super(fullName, monthlyIncome);
         this.setNbHoursPerWeek(20);
     }
+
+    @Override
+    public double calculateTax() {
+        TaxCalculator<PartTimeEmployee> taxCalculator = new PartTimeEmployeeTaxCalculator();
+        return taxCalculator.calculate(this);
+    }
 }

src/oops/SOLID/openClosePrinciple/before/taxes/FullTimeEmployeeTaxCalculator.java

@@ -0,0 +1,17 @@
+package oops.SOLID.openClosePrinciple.before.taxes;
+
+import oops.SOLID.openClosePrinciple.before.employees.Employee;
+import oops.SOLID.openClosePrinciple.before.employees.FullTimeEmployee;
+
+public class FullTimeEmployeeTaxCalculator implements TaxCalculator<FullTimeEmployee> {
+    private static final Integer INCOME_TAX = 30;
+    private static final Integer PROFESSIONAL_TAX = 2;
+    private static final Integer EDUCATION_CESS = 1;
+
+    @Override
+    public double calculate(FullTimeEmployee employee) {
+        Integer income = employee.getMonthlyIncome();
+        return income * INCOME_TAX / 100 + income * PROFESSIONAL_TAX / 100
+                + income * EDUCATION_CESS / 100;
+    }
+}

src/oops/SOLID/openClosePrinciple/before/taxes/InternTaxCalculator.java

@@ -0,0 +1,15 @@
+package oops.SOLID.openClosePrinciple.before.taxes;
+
+import oops.SOLID.openClosePrinciple.before.employees.Intern;
+
+public class InternTaxCalculator implements TaxCalculator<Intern> {
+    @Override
+    public double calculate(Intern employee) {
+        Integer income = employee.getMonthlyIncome();
+        if (income < 300000) {
+            return 0;
+        } else {
+            return income * 15 / 100;
+        }
+    }
+}

src/oops/SOLID/openClosePrinciple/before/taxes/PartTimeEmployeeTaxCalculator.java

@@ -0,0 +1,17 @@
+package oops.SOLID.openClosePrinciple.before.taxes;
+
+import oops.SOLID.openClosePrinciple.before.employees.Employee;
+import oops.SOLID.openClosePrinciple.before.employees.PartTimeEmployee;
+
+public class PartTimeEmployeeTaxCalculator implements TaxCalculator<PartTimeEmployee> {
+    private static final Integer INCOME_TAX = 20;
+    private static final Integer PROFESSIONAL_TAX = 3;
+    private static final Integer EDUCATION_CESS = 1;
+
+    @Override
+    public double calculate(PartTimeEmployee employee) {
+        Integer income = employee.getMonthlyIncome();
+        return income * INCOME_TAX / 100 + income * PROFESSIONAL_TAX / 100
+                + income * EDUCATION_CESS / 100;
+    }
+}

src/oops/SOLID/openClosePrinciple/before/taxes/TaxCalculator.java

@@ -2,15 +2,6 @@
 
 import oops.SOLID.openClosePrinciple.before.employees.Employee;
 
-public class TaxCalculator {
-    private final static int INCOME_TAX_PERCENTAGE = 20;
-    private final static int PROFESSIONAL_TAX_PERCENTAGE = 3;
-
-
-    public static double calculate(Employee employee) {
-        return 
-                (employee.getMonthlyIncome() * PROFESSIONAL_TAX_PERCENTAGE) / 100 +
-                (employee.getMonthlyIncome() * INCOME_TAX_PERCENTAGE) / 100;
-
-    }
+public interface TaxCalculator<T extends Employee> {
+    double calculate(T employee);
 }

src/oops/SOLID/singleResponsibilityPrinciple/before/Employee.java

@@ -14,7 +14,7 @@ public abstract class Employee {
     private int monthlyIncome;
     private int nbHoursPerWeek;
 
-    public Employee(String fullName, int monthlyIncome){
+    public Employee(String fullName, int monthlyIncome) {
         setMonthlyIncome(monthlyIncome);
 
         String[] names = fullName.split(" ");
@@ -40,7 +40,7 @@ public int getMonthlyIncome() {
     }
 
     public void setMonthlyIncome(int monthlyIncome) {
-        if(monthlyIncome < 0){
+        if (monthlyIncome < 0) {
             throw new IllegalArgumentException("Income must be positive");
         }
 
@@ -52,43 +52,33 @@ public int getNbHoursPerWeek() {
     }
 
     public void setNbHoursPerWeek(int nbHoursPerWeek) {
-        if(nbHoursPerWeek <= 0){
+        if (nbHoursPerWeek <= 0) {
             throw new IllegalArgumentException("Income must be positive");
         }
 
         this.nbHoursPerWeek = nbHoursPerWeek;
     }
 
-    public String getFullName(){
+    public String getFullName() {
         return this.firstName + " " + this.lastName;
     }
 
-    public  void save(){
-        try {
-        	Employee employee =this;
-            StringBuilder sb = new StringBuilder();
-            sb.append("### EMPLOYEE RECORD ####");
-            sb.append(System.lineSeparator());
-            sb.append("NAME: ");
-            sb.append(employee.firstName + " " + employee.lastName);
-            sb.append(System.lineSeparator());
-            sb.append("POSITION: ");
-            sb.append(employee.getClass().getTypeName());
-            sb.append(System.lineSeparator());
-            sb.append("EMAIL: ");
-            sb.append(employee.getEmail());
-            sb.append(System.lineSeparator());
-            sb.append("MONTHLY WAGE: ");
-            sb.append(employee.monthlyIncome);
-            sb.append(System.lineSeparator());
-
-            Path path = Paths.get(employee.getFullName()
-                    .replace(" ","_") + ".rec");
-            Files.write(path, sb.toString().getBytes());
-
-            System.out.println("Saved employee " + employee.toString());
-        } catch (IOException e){
-            System.out.println("ERROR: Could not save employee. " + e);
-        }
+    public String serializeData() {
+        StringBuilder sb = new StringBuilder();
+        sb.append("### EMPLOYEE RECORD ####");
+        sb.append(System.lineSeparator());
+        sb.append("NAME: ");
+        sb.append(this.getFullName());
+        sb.append(System.lineSeparator());
+        sb.append("POSITION: ");
+        sb.append(this.getClass().getTypeName());
+        sb.append(System.lineSeparator());
+        sb.append("EMAIL: ");
+        sb.append(this.getEmail());
+        sb.append(System.lineSeparator());
+        sb.append("MONTHLY WAGE: ");
+        sb.append(this.getMonthlyIncome());
+        sb.append(System.lineSeparator());
+        return sb.toString();
     }
 }

src/oops/SOLID/singleResponsibilityPrinciple/before/EmployeeRepository.java

@@ -1,5 +1,9 @@
 package oops.SOLID.singleResponsibilityPrinciple.before;
 
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
 import java.util.Arrays;
 import java.util.List;
 
@@ -16,4 +20,20 @@ public List<Employee> findAll(){
 
         return Arrays.asList(anna, billy, steve, magda);
     }
+
+    public  void save(Employee employee){
+        try {
+            String employeeData = employee.serializeData();
+
+            Path path = Paths.get(employee.getFullName()
+                    .replace(" ","_") + ".rec");
+            Files.write(path, employeeData.getBytes());
+
+            System.out.println("Saved employee " + employee.toString());
+        } catch (IOException e){
+            System.out.println("ERROR: Could not save employee. " + e);
+        }
+    }
+
+
 }