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  1. // -------- State Interface --------
  2. interface State {
  3.     void insertCoin();
  4.     void turnCrank();
  5. }
  6.  
  7. // -------- No Coin State --------
  8. class NoCoinState implements State {
  9.     GumballMachine machine;
  10.  
  11.     NoCoinState(GumballMachine m) { this.machine = m; }
  12.  
  13.     public void insertCoin() {
  14.         System.out.println("Coin inserted.");
  15.         machine.setState(machine.hasCoinState);
  16.     }
  17.  
  18.     public void turnCrank() {
  19.         System.out.println("Insert coin first.");
  20.     }
  21. }
  22.  
  23. // -------- Has Coin State --------
  24. class HasCoinState implements State {
  25.     GumballMachine machine;
  26.  
  27.     HasCoinState(GumballMachine m) { this.machine = m; }
  28.  
  29.     public void insertCoin() {
  30.         System.out.println("Coin already inserted.");
  31.     }
  32.  
  33.     public void turnCrank() {
  34.         System.out.println("Crank turned. Dispensing...");
  35.         machine.releaseBall();
  36.         if (machine.count > 0)
  37.             machine.setState(machine.noCoinState);
  38.         else
  39.             machine.setState(machine.soldOutState);
  40.     }
  41. }
  42.  
  43. // -------- Sold Out State --------
  44. class SoldOutState implements State {
  45.     GumballMachine machine;
  46.  
  47.     SoldOutState(GumballMachine m) { this.machine = m; }
  48.  
  49.     public void insertCoin() {
  50.         System.out.println("Machine is sold out.");
  51.     }
  52.  
  53.     public void turnCrank() {
  54.         System.out.println("Nothing happens, sold out.");
  55.     }
  56. }
  57.  
  58. // -------- Gumball Machine --------
  59. class GumballMachine {
  60.     State noCoinState;
  61.     State hasCoinState;
  62.     State soldOutState;
  63.     State state;
  64.  
  65.     int count = 0;
  66.  
  67.     public GumballMachine(int gumballs) {
  68.         noCoinState = new NoCoinState(this);
  69.         hasCoinState = new HasCoinState(this);
  70.         soldOutState = new SoldOutState(this);
  71.  
  72.         count = gumballs;
  73.         state = (count > 0) ? noCoinState : soldOutState;
  74.     }
  75.  
  76.     void setState(State s) { state = s; }
  77.  
  78.     void releaseBall() {
  79.         System.out.println("A gumball comes out...");
  80.         if (count > 0) count--;
  81.     }
  82.  
  83.     // Public API
  84.     void insertCoin() { state.insertCoin(); }
  85.     void turnCrank() { state.turnCrank(); }
  86. }
  87.  
  88. // -------- Test --------
  89. public class Main {
  90.     public static void main(String[] args) {
  91.         GumballMachine gm = new GumballMachine(2);
  92.  
  93.         gm.insertCoin();
  94.         gm.turnCrank();
  95.  
  96.         gm.insertCoin();
  97.         gm.turnCrank();
  98.  
  99.         gm.insertCoin();   // Should say sold out
  100.         gm.turnCrank();
  101.     }
  102. }
Success #stdin #stdout 0.08s 54608KB
comments (?)
stdin 
Standard input is empty
stdout 
Coin inserted.
Crank turned. Dispensing...
A gumball comes out...
Coin inserted.
Crank turned. Dispensing...
A gumball comes out...
Machine is sold out.
Nothing happens, sold out.
https://ideone.com/GLStBX
Gumball java
language:
Java (12.0.1)
created:
2 days ago
visibility:
public

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