Homework#1 Example

homework1.java

public class Mobile{
  private Keyboard keyboard;
  private Screen  screen;
  private Stack callStack;
  private State   phoneState;
  private String currentNumber;

  enum State{
    on,
    off,
    onCall
  }

  public static void main(String[] args){

  }

  public Mobile(){
    this.keyboard = new Keyboard();
    this.screen   = new Screen();
    this.speaker  = new Speaker();
  }

  private void onKeyPressed(){
    Key key = keyboard.pressedKey();
    
    // when telephone is standing by (at-home state)
    if(phoneState == State.on){
      if(key.keyType == Key.KeyType.number){
        this.updateScreen(key.value);
        this.updateCurrentNumber;
      }
      else{
        if(key.value == "call"){
          this.call(this.currentNumber);
        }
        else if(key.value == "end_call"){
          this.endCall();
          if(!callStack.isEmpty){
            this.resumeCall();
          }
        }
        else{
          this.turnOff;
        }
      }
    }
    // when mobile is off
    else if(phoneState == State.off){
      if(key.value == "turn_on")
        this.turnOn();
    }
    // when the phone is on a call
    else if(phoneState == State.onCall){
      if(key.value == "call"){
        // pause current call, getting a new call
        this.pauseCurrentCall();
        this.receiveCall;
      }
    }
  }

  private turnOn(){}

  private turnOff(){}

  private call(String number){}

  private pauseCurrentCall(){
    this.callStack.push(this.currentNumber);
    this.currenNumber = newNumber; // it's not defined here, but suppose this existed
  }

  private resumeCall(){}

  private endCall(){
    this.callStack.pop();
  }

  private receiveCall(){}

  private void updateScreen(String value){
    this.screen.append(value);
  }
  private void updateCurrentNumber(String value){
    this.currentNumber = this.currentNumber + value;
  }


}

public class Keyboard{
  public Key[] keys;
  public Keyboard(){
    this.keys = {
      new Key("1","1", Key.KeyType.number),
      new Key("3", Key.KeyType.number),new Key("4", Key.KeyType.number),
      new Key("5", Key.KeyType.number),new Key("6", Key.KeyType.number),
      new Key("7", Key.KeyType.number),new Key("8", Key.KeyType.number),
      new Key("9", Key.KeyType.number),new Key("0", Key.KeyType.number),
      new Key("call", Key.KeyType.command), new Key("end_call", Key.KeyType.command)
    }
  }
  public void pressedKey(){
    // return instance of Key that is pressed
  }
}

public class Key{
  public String label;
  public String value;
  public KeyType keyType;
  enum KeyType{
    number,
    command
  }

  public Key(String label, String value, KeyType keyType){
    this.label   = label;
    this.value   = value;
    this.keyType = keyType;
  }
  public Key(String label, KeyType keyType){
    this(label, label);
  }
}

public class Screen{
  private String output;
  private Stack screenStack;
  public void clear(){
    screenStack.clear();
  }
  public void append(String text){
    screenStack.push(text);
  }
  public void delete(){
    screenStack.pop();
  }
  public void showOutput(String text){
    //print output on real screen

  }
}

public class Stack{
  public Stack(){

  }
  public Object pop(){

  }
  public Object push(){

  }
  public Object topOfStack(){

  }
  public Object clear(){

  }
  public Object reversePopAll(){

  }
  public boolean isEmpty{

  }
}