WareContext.java

package com.company;
import javax.swing.*;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.util.*;
import java.text.*;
import java.io.*;

public class WareContext {
    private int currentState;
    private static WareContext context;
    private int currentUser = 0;
    private int userID;
    private WareState[] states;
    private int[][] nextState;
    private static JFrame wareFrame;

    private WareContext() {
        states = new WareState[6];
        states[0] = LoginState.instance();
        states[1] = ClientUI.instance();
        states[2] = ClerkState.instance();
        states[3] = ManagerState.instance();
        states[4] = ModifyCartState.instance();
        states[5] = ClientQuery.instance();

        nextState = new int[6][6];
        nextState[0][0]= -1;nextState[0][1]= 1;nextState[0][2]= 2;nextState[0][3]= 3;nextState[0][4]= -2;nextState[0][5]= -2;
        nextState[1][0]= 0;nextState[1][1]= -2;nextState[1][2]= -2;nextState[1][3]= -2;nextState[1][4]= 4;nextState[1][5]= -2;
        nextState[2][0]= 0;nextState[2][1]= 4;nextState[2][2]= -2;nextState[2][3]= -2;nextState[2][4]= -2;nextState[2][5]= 4;
        nextState[3][0]= 0;nextState[3][1]= -2;nextState[3][2]= 4;nextState[3][3]= -2;nextState[3][4]= -2;nextState[3][5]= -2;
        nextState[4][0]= 0;nextState[4][1]= 4;nextState[4][2]= -2;nextState[4][3]= -2;nextState[4][4]= -2;nextState[4][5]= -2;
        nextState[5][0]= 0;nextState[5][1]= -2;nextState[5][2]= 4;nextState[5][3]= -2;nextState[5][4]= -2;nextState[5][5]=-2;
        currentState = 0;

        wareFrame = new JFrame("Warehouse GUI");

        wareFrame.addWindowListener(new WindowAdapter()
        {public void windowClosing(WindowEvent e){System.exit(0);}});

        wareFrame.setSize(400,400);
        wareFrame.setLocation(400,400);
    }
    public void changeState(int transition) {
        currentState = nextState[currentState][transition];
        if (currentState == -2) {
            System.out.println("Error has occurred");
            terminate();
        }
        if (currentState == -1)
            terminate();
        if (currentState == 4)
            saveUser(transition);
        if (currentState == 0)
            savedUser();
        System.out.println(currentState);
        states[currentState].run();
    }

    private void terminate() {
        System.out.println(" Goodbye \n ");
        System.exit(0);
    }
    private void saveUser (int user) {
        currentUser += user;
        currentState = user;
        //currentUser = 1, clerk as client
        //currentUser = 2, manager as clerk
        //currentUser = 3, manager as clerk as client
        //currentUser = 4, Clerk's modify cart state
        //currentUser = 5, ClientQuery state
    }
    private void savedUser () {
        if (currentUser == 2) {
            currentUser -= 2;
            currentState = 3;
        } else if (currentUser == 1 || currentUser == 3) {
            --currentUser;
            currentState = 2;
        }
        // manager as clerk back to manager
        //(manager as) clerk as client back to clerk
    }
    public void setUID (int uid) {
        userID = uid;
    }
    public int getUID () {
        return userID;
    }
    public static WareContext instance() {
        if (context == null) {
            return context = new WareContext();
        } else {
            return context;
        }
    }

    public JFrame getFrame()
    {
        return wareFrame;
    }

    public void process() {
        states[currentState].run();
    }

    public static void main(String[] args) {
        WareContext.instance().process();
    }
}