Implemented functions and signatures from Staff UML diagram.

SchedulerApp/src/main/java/com/example/schedulerapp/Staff.java

 package com.example.schedulerapp;
 
+import java.util.ArrayList;
+import java.util.List;
+
 public class Staff {
+    /*
+    Test to see if this works with 'final' key word.
+     */
+    private final List<Employee> allStaff = new ArrayList<>();
+
+    public void addEmployee(String name, String position, float wage, String number, boolean manager, Shift[] availability) {
+        int ID = 0;
+        if (allStaff.size() > 0) {
+            ID = allStaff.get(allStaff.size() - 1).getID() + 1;
+        }
+        Employee newEmployee = new Employee(name, position, wage, number, manager, availability, ID);
+        this.allStaff.add(newEmployee);
+    }
+
+    public void removeEmployee(int ID) {
+        for (Employee employee: allStaff) {
+            if (employee.getID() == ID) {
+                allStaff.remove(employee);
+                break;
+            }
+        }
+    }
+
+    /*
+    Not finished. Names are not unique. Although, getting employees by name is convenient.
+     */
+    public void removeEmployee(String name) {
+        for (Employee employee: allStaff) {
+            if (employee.getName().equals(name)) {
+                allStaff.remove(employee);
+                break;
+            }
+        }
+    }
+
+    public Employee getEmployee(int ID) {
+        for (Employee employee: allStaff) {
+            if (employee.getID() == ID) {
+                return employee;
+            }
+        }
+        return null;
+    }
+
+    /*
+    Not finished. Names are not unique. Although, getting employees by name is convenient.
+     */
+    public Employee getEmployee(String name) {
+        for (Employee employee: allStaff) {
+            if (employee.getName().equals(name)) {
+                return employee;
+            }
+        }
+        return null;
+    }
+
+    public List<Employee> getAllStaff() {
+        return allStaff;
+    }
 }