init account interface

org/university/core/AbstractEmployee.java

@@ -43,7 +43,5 @@ public abstract class AbstractEmployee extends Person{
         return false;
     }
 
-    abstract public double getCurrentIncome();
-
     abstract public boolean isPromotable();
 }

org/university/core/Account.java

+package org.university.core;
 
+public interface Account{
+    public int balance;
+
+    public int getCurrentIncome();
+    public void checkout();
+}

org/university/core/GraduateStudent.java

@@ -2,8 +2,9 @@ package org.university.core;
 
 import java.util.*;
 
-public class GraduateStudent extends Student{
+public class GraduateStudent extends Student implements Account{
     private ArrayList<Article> articles;
+    private ArrayList<Statement> ;
 
     public GraduateStudent(String name, int entranceYear, int id){
         super(name, entranceYear, id);
@@ -16,6 +17,14 @@ public class GraduateStudent extends Student{
         return arr;
     }
 
+    public Statement checkout(){
+        int amount = getCurrentIncome();
+        balance += amount;
+        Statement statement = new Statement(amount, new Date(), (Account)this);
+        addBankStatement(statement);
+        return statement;
+    }
+
     public void addArticle(Article c){
         articles.add(c);
     }

org/university/core/Professor.java

@@ -2,7 +2,7 @@ package org.university.core;
 
 import java.util.*;
 
-public class Professor extends AbstractEmployee{
+public class Professor extends AbstractEmployee implements Account{
     private ArrayList<Course> courses;
     private String group;
 
@@ -10,9 +10,18 @@ public class Professor extends AbstractEmployee{
         super(name, entranceYear, id);
         courses = new ArrayList<>();
         basicIncome = 7000;
+        balance = 0;
     }
 
-    public double getCurrentIncome(){
+    public Statement checkout(){
+        int amount = getCurrentIncome();
+        balance += amount;
+        Statement statement = new Statement(amount, new Date(), (Account)this);
+        addBankStatement(statement);
+        return statement;
+    }
+
+    public int getCurrentIncome(){
         return courses.size() * 1000 + basicIncome; 
     }
 

org/university/core/ServiceEmaployee.java

@@ -2,7 +2,7 @@ package org.university.core;
 
 import java.util.*;
 
-public class ServiceEmaployee extends AbstractEmployee{
+public class ServiceEmaployee extends AbstractEmployee implements Account{
     public int extraWork;
 
     public ServiceEmaployee(String name, int entranceYear, int id){
@@ -18,6 +18,14 @@ public class ServiceEmaployee extends AbstractEmployee{
         return extraWork;
     }
 
+    public Statement checkout(){
+        int amount = getCurrentIncome();
+        balance += amount;
+        Statement statement = new Statement(amount, new Date(), (Account)this);
+        addBankStatement(statement);
+        return statement;
+    }
+
     public double getCurrentIncome(){
         return extraWork * 500 + basicIncome; 
     }

org/university/core/Statement.java

@@ -5,9 +5,9 @@ import java.util.*;
 public class Statement{
     private int amount;
     private Date date;
-    private AbstractEmployee receiver;
+    private Account receiver;
 
-    public Statement(int amount, Date date, AbstractEmployee receiver){
+    public Statement(int amount, Date date, Account receiver){
         this.amount = amount;
         this.date = date;
         this.receiver = receiver;