Changes for SRP and LS principles by Vinit from Oct-Nov SuperX batch

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

@@ -1,6 +1,8 @@
 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?
@@ -14,19 +16,31 @@
  * so objects of ArrayList are not fully replaceable by the objects of stack.   
  * 
  */
-public class StackWrong extends ArrayList<Integer>{
-	private int topPointer = 0;
-
+public class StackWrong{
+	private int topPointer;
+	private List<Integer> arrLi;
+
+	public StackWrong(){
+		this.arrLi = new ArrayList<>();
+		this.topPointer = 0;
+	}
+
 	public void push(Integer a) {
-		add(topPointer, a);
+		arrLi.add(a);
 		topPointer++;
 	}	
-	public void pop() {
-		remove(topPointer-1);
+	public void pop() throws NullPointerException{
+		if(topPointer == 0) throw new NullPointerException("No elements in stack");
+		arrLi.remove(topPointer-1);
 		topPointer--;
 	}
 	public Integer top() {
-		return get(topPointer-1);
+		if(topPointer == 0) throw new NullPointerException("No elements in stack");
+		return arrLi.get(topPointer-1);
+	}
+	public void clear(){
+		arrLi.clear();
+		topPointer = 0;
 	}
 
 	public static void main(String[] args) {

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

@@ -1,10 +1,5 @@
 package oops.SOLID.singleResponsibilityPrinciple.before;
 
-import java.io.IOException;
-import java.nio.file.Files;
-import java.nio.file.Path;
-import java.nio.file.Paths;
-
 /*
 Models an employee form a business perspective
  */
@@ -62,33 +57,4 @@ public void setNbHoursPerWeek(int nbHoursPerWeek) {
     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);
-        }
-    }
 }

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

@@ -0,0 +1,24 @@
+package oops.SOLID.singleResponsibilityPrinciple.before;
+
+import java.util.List;
+
+public class EmployeeList {
+    private static EmployeeList instance;
+    private static List<Employee> employeeList;
+    private EmployeeList(){
+
+    }
+
+    public static EmployeeList getInstance(){
+        if(instance == null){
+            synchronized (EmployeeList.class){
+                if(instance == null) instance = new EmployeeList();
+            }
+        }
+        return instance;
+    }
+
+    public List<Employee> getEmployeeList(){
+        return employeeList;
+    }
+}

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

@@ -1,19 +1,51 @@
 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;
 
 public class EmployeeRepository {
 
     public List<Employee> findAll(){
-
+        return EmployeeList.getInstance().getEmployeeList();
         // Employees are kept in memory for simplicity
-        Employee anna = new FullTimeEmployee("Anna Smith", 2000);
-        Employee billy = new FullTimeEmployee("Billy Leech", 920);
+    }
+
+    public void saveAll(List<Employee> empLi){
+        for(Employee employee : empLi){
+            try {
+                StringBuilder sb = new StringBuilder();
+                sb.append("### EMPLOYEE RECORD ####");
+                sb.append(System.lineSeparator());
+                sb.append("NAME: ");
+                sb.append(employee.getFullName());
+                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.getMonthlyIncome());
+                sb.append(System.lineSeparator());
+
+                Path path = Paths.get(employee.getFullName()
+                        .replace(" ","_") + ".rec");
+
+                Files.write(path, sb.toString().getBytes());
+
+                EmployeeList.getInstance().getEmployeeList().add(employee);
+
+                System.out.println("Saved employee " + employee.toString());
 
-        Employee steve = new PartTimeEmployee("Steve Jones", 800);
-        Employee magda = new PartTimeEmployee("Magda Iovan", 920);
 
-        return Arrays.asList(anna, billy, steve, magda);
+            } catch (IOException e){
+                System.out.println("ERROR: Could not save employee. " + e);
+            }
+        }
     }
 }

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

@@ -5,12 +5,15 @@
 public class SaveEmployeesMain {
     public static void main(String[] args) {
         // Grab employees
+        List<Employee> empLi = List.of(new FullTimeEmployee("Anna Smith", 2000),
+                                       new FullTimeEmployee("Billy Leech", 920),
+                                       new PartTimeEmployee("Steve Jones", 800),
+                                       new PartTimeEmployee("Magda Iovan", 920));
+
         EmployeeRepository repository = new EmployeeRepository();
         List<Employee> employees = repository.findAll();
 
         // Save all
-        for (Employee e : employees){
-            e.save();
-        }
+        repository.saveAll(empLi);
     }
 }