refactored code

src/main/java/com/napier/sem/App.java

@@ -71,129 +71,6 @@ public void disconnect()
         }
     }
 
-    public List<Employee> getEmployeeWithTitile(String title)
-    {
-        List<Employee> employees = new ArrayList<Employee>();
-
-        try
-        {
-            // Create an SQL prepared statement to prevent SQL injection
-            String strSelect =
-                    "SELECT employees.emp_no, employees.first_name, employees.last_name, salaries.salary " +
-                            "FROM employees, salaries, titles " +
-                            "WHERE employees.emp_no = salaries.emp_no " +
-                            "AND employees.emp_no = titles.emp_no " +
-                            "AND salaries.to_date = '9999-01-01' " +
-                            "AND titles.to_date = '9999-01-01' " +
-                            "AND titles.title = ? " +  // Use a placeholder for title
-                            "ORDER BY employees.emp_no ASC";
-
-            // Prepare statement
-            PreparedStatement pstmt = con.prepareStatement(strSelect);
-            // Set the title parameter
-            pstmt.setString(1, title);
-
-            // Execute SQL statement
-            ResultSet rset = pstmt.executeQuery();
-
-            // Return new employee if valid.
-            while (rset.next())
-            {
-                Employee emp = new Employee();
-                emp.emp_no = rset.getInt("emp_no");
-                emp.first_name = rset.getString("first_name");
-                emp.last_name = rset.getString("last_name");
-                emp.salary = rset.getInt("salary");
-                employees.add(emp);
-            }
-            return employees;
-        }
-        catch (Exception e)
-        {
-            System.out.println(e.getMessage());
-            System.out.println("Failed to get employee details");
-            return null;
-        }
-    }
-
-
-    /**
-     * Gets all the current employees and salaries.
-     * @return A list of all employees and salaries, or null if there is an error.
-     */
-    public ArrayList<Employee> getAllSalaries()
-    {
-        try
-        {
-            // Create an SQL statement
-            Statement stmt = con.createStatement();
-            // Create string for SQL statement
-            String strSelect =
-                    "SELECT employees.emp_no, employees.first_name, employees.last_name, salaries.salary "
-                            + "FROM employees, salaries "
-                            + "WHERE employees.emp_no = salaries.emp_no AND salaries.to_date = '9999-01-01' "
-                            + "ORDER BY employees.emp_no ASC";
-            // Execute SQL statement
-            ResultSet rset = stmt.executeQuery(strSelect);
-            // Extract employee information
-            ArrayList<Employee> employees = new ArrayList<Employee>();
-            while (rset.next())
-            {
-                Employee emp = new Employee();
-                emp.emp_no = rset.getInt("employees.emp_no");
-                emp.first_name = rset.getString("employees.first_name");
-                emp.last_name = rset.getString("employees.last_name");
-                emp.salary = rset.getInt("salaries.salary");
-                employees.add(emp);
-            }
-            return employees;
-        }
-        catch (Exception e)
-        {
-            System.out.println(e.getMessage());
-            System.out.println("Failed to get salary details");
-            return null;
-        }
-    }
-
-    /**
-     * Prints a list of employees.
-     * @param employees The list of employees to print.
-     */
-    public void printSalaries(ArrayList<Employee> employees)
-    {
-        if (employees == null){
-            System.out.println("No employees");
-            return;
-        }
-        // Print header
-        System.out.println(String.format("%-10s %-15s %-20s %-8s", "Emp No", "First Name", "Last Name", "Salary"));
-        // Loop over all employees in the list
-        for (Employee emp : employees)
-        {
-            if (emp == null)
-                continue;
-            String emp_string =
-                    String.format("%-10s %-15s %-20s %-8s",
-                            emp.emp_no, emp.first_name, emp.last_name, emp.salary);
-            System.out.println(emp_string);
-        }
-    }
-
-    public void displayEmployeeWithTitle(List<Employee> emp)
-    {
-        if (emp != null && !emp.isEmpty())
-        {
-            System.out.println(String.format("%-10s %-15s %-20s %-8s", "Emp No", "First Name", "Last Name", "Title" ,"Salary"));
-            for (Employee employee : emp) {
-                String displayString =
-                        String.format("%-10s %-15s %-20s %-8s",
-                        employee.emp_no, employee.first_name, employee.last_name, " Engineer", employee.salary );
-                System.out.println(displayString);
-            }
-        }
-    }
-
     public static void main(String[] args)
     {
         // Create new Application
@@ -202,15 +79,18 @@ public static void main(String[] args)
         // Connect to database
         a.connect();
 
+        EmployeeSQL employeeSQL = new EmployeeSQL(a.con);
+        EmployeeDisplay employeeDisplay = new EmployeeDisplay();
+
         // get Employee who are Engineers database
-        List<Employee> emp = a.getEmployeeWithTitile("Engineer");
-        a.displayEmployeeWithTitle(emp);
+        List<Employee> emp = employeeSQL.getEmployeeWithTitle("Engineer");
+        // display employee with title
+        employeeDisplay.displayEmployeeWithTitle(emp);
 
-        ArrayList<Employee> emp1 = a.getAllSalaries();
-        a.printSalaries(emp1);
+        ArrayList<Employee> emp1 = employeeSQL.getAllSalaries();
+        employeeDisplay.printSalaries(emp1);
 
         // Disconnect from database
         a.disconnect();
-
     }
 }

src/main/java/com/napier/sem/EmployeeDisplay.java

@@ -0,0 +1,46 @@
+package com.napier.sem;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class EmployeeDisplay {
+
+    /**
+     * Prints a list of employees.
+     * @param employees The list of employees to print.
+     */
+    public void printSalaries(ArrayList<Employee> employees)
+    {
+        if (employees == null){
+            System.out.println("No employees");
+            return;
+        }
+        // Print header
+        System.out.println(String.format("%-10s %-15s %-20s %-8s", "Emp No", "First Name", "Last Name", "Salary"));
+        // Loop over all employees in the list
+        for (Employee emp : employees)
+        {
+            if (emp == null)
+                continue;
+            String emp_string =
+                    String.format("%-10s %-15s %-20s %-8s",
+                            emp.emp_no, emp.first_name, emp.last_name, emp.salary);
+            System.out.println(emp_string);
+        }
+    }
+
+    public void displayEmployeeWithTitle(List<Employee> emp)
+    {
+        if (emp != null && !emp.isEmpty())
+        {
+            System.out.println(String.format("%-10s %-15s %-20s %-8s", "Emp No", "First Name", "Last Name", "Title" ,"Salary"));
+            for (Employee employee : emp) {
+                String displayString =
+                        String.format("%-10s %-15s %-20s %-8s",
+                                employee.emp_no, employee.first_name, employee.last_name, " Engineer", employee.salary );
+                System.out.println(displayString);
+            }
+        }
+    }
+
+}

src/main/java/com/napier/sem/EmployeeSQL.java

@@ -0,0 +1,84 @@
+package com.napier.sem;
+
+import java.sql.Connection;
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.sql.Statement;
+import java.util.ArrayList;
+import java.util.List;
+
+public class EmployeeSQL {
+
+    private Connection con;
+
+    public EmployeeSQL(Connection con) {
+        this.con = con;
+    }
+
+    public List<Employee> getEmployeeWithTitle(String title) {
+        List<Employee> employees = new ArrayList<>();
+
+        try {
+            String strSelect =
+                    "SELECT employees.emp_no, employees.first_name, employees.last_name, salaries.salary " +
+                            "FROM employees " +
+                            "JOIN salaries ON employees.emp_no = salaries.emp_no " +
+                            "JOIN titles ON employees.emp_no = titles.emp_no " +
+                            "WHERE salaries.to_date = '9999-01-01' " +
+                            "AND titles.to_date = '9999-01-01' " +
+                            "AND titles.title = ? " +
+                            "ORDER BY employees.emp_no ASC";
+
+            PreparedStatement pstmt = con.prepareStatement(strSelect);
+            pstmt.setString(1, title);
+            ResultSet rset = pstmt.executeQuery();
+
+            while (rset.next()) {
+                Employee emp = new Employee();
+                emp.emp_no = rset.getInt("emp_no");
+                emp.first_name = rset.getString("first_name");
+                emp.last_name = rset.getString("last_name");
+                emp.salary = rset.getInt("salary");
+                employees.add(emp);
+            }
+            rset.close();
+            pstmt.close();
+            return employees;
+        } catch (Exception e) {
+            e.printStackTrace();
+            System.out.println("Failed to get employee details");
+            return null;
+        }
+    }
+
+    public ArrayList<Employee> getAllSalaries() {
+        ArrayList<Employee> employees = new ArrayList<>();
+        try {
+            String strSelect =
+                    "SELECT employees.emp_no, employees.first_name, employees.last_name, salaries.salary " +
+                            "FROM employees " +
+                            "JOIN salaries ON employees.emp_no = salaries.emp_no " +
+                            "WHERE salaries.to_date = '9999-01-01' " +
+                            "ORDER BY employees.emp_no ASC";
+
+            Statement stmt = con.createStatement();
+            ResultSet rset = stmt.executeQuery(strSelect);
+
+            while (rset.next()) {
+                Employee emp = new Employee();
+                emp.emp_no = rset.getInt("emp_no");
+                emp.first_name = rset.getString("first_name");
+                emp.last_name = rset.getString("last_name");
+                emp.salary = rset.getInt("salary");
+                employees.add(emp);
+            }
+            rset.close();
+            stmt.close();
+            return employees;
+        } catch (Exception e) {
+            e.printStackTrace();
+            System.out.println("Failed to get salary details");
+            return null;
+        }
+    }
+}

src/test/java/com/napier/devops/AppTest.java

@@ -2,19 +2,20 @@
 
 import com.napier.sem.App;
 import com.napier.sem.Employee;
+import com.napier.sem.EmployeeDisplay;
 import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.Test;
 
 import java.util.ArrayList;
 
 public class AppTest
 {
-    static App app;
+    static EmployeeDisplay app;
 
     @BeforeAll
     static void init()
     {
-        app = new App();
+        app = new EmployeeDisplay();
     }
 
     // null

target/surefire-reports/TEST-com.napier.devops.AppTest.xml

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<testsuite xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="https://maven.apache.org/surefire/maven-surefire-plugin/xsd/surefire-test-report.xsd" name="com.napier.devops.AppTest" time="0.009" tests="4" errors="0" skipped="0" failures="0">
+<testsuite xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="https://maven.apache.org/surefire/maven-surefire-plugin/xsd/surefire-test-report.xsd" name="com.napier.devops.AppTest" time="0.016" tests="4" errors="0" skipped="0" failures="0">
   <properties>
     <property name="idea.version" value="2024.2.2"/>
     <property name="java.runtime.name" value="OpenJDK Runtime Environment"/>
@@ -64,7 +64,7 @@
     <property name="sun.stdout.encoding" value="UTF-8"/>
     <property name="sun.cpu.isalist" value="amd64"/>
   </properties>
-  <testcase name="printSalariesTestContainsNull" classname="com.napier.devops.AppTest" time="0.005"/>
+  <testcase name="printSalariesTestContainsNull" classname="com.napier.devops.AppTest" time="0.009"/>
   <testcase name="printSalariesTestEmpty" classname="com.napier.devops.AppTest" time="0"/>
   <testcase name="printSalariesTestNull" classname="com.napier.devops.AppTest" time="0"/>
   <testcase name="printSalaries" classname="com.napier.devops.AppTest" time="0.001"/>

target/surefire-reports/com.napier.devops.AppTest.txt

@@ -1,4 +1,4 @@
 -------------------------------------------------------------------------------
 Test set: com.napier.devops.AppTest
 -------------------------------------------------------------------------------
-Tests run: 4, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.009 sec - in com.napier.devops.AppTest
+Tests run: 4, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.016 sec - in com.napier.devops.AppTest