public class WindowState { 
  private String stateValue; 
   
  public WindowState(String stateValue) { 
    this.stateValue = stateValue; 
  } 
   
  public String getStateValue() { 
    return stateValue; 
  } 
 
  public void setStateValue(String stateValue) { 
    this.stateValue = stateValue; 
  } 
   
  public void handle() { 
    /* 
     * 根据不同状态做不同操作， 再切换状态 
     */ 
    if ("窗口".equals(stateValue)) { 
      switchWindow(); 
      this.stateValue = "全屏"; 
    } else if ("全屏".equals(stateValue)) { 
      switchFullscreen(); 
      this.stateValue = "窗口"; 
    } 
  } 
   
  private void switchWindow() { 
    System.out.println("切换为窗口状态"); 
  } 
   
  private void switchFullscreen() { 
    System.out.println("切换为全屏状态"); 
  } 
   
} 

/** 
 * 状态的使用 
 */ 
public class WindowContext { 
  private WindowState state; 
   
  public WindowContext(WindowState state) { 
    this.state = state; 
  } 
   
  public WindowState getState() { 
    return state; 
  } 
   
  public void setState(WindowState state) { 
    this.state = state; 
  } 
   
  public void switchState() { 
    this.state.handle(); 
  } 
} 

/* 
 * 状态(State)模式 行为型模式 
 * 既改变对象的状态，又改变对象的行为 
 * 根据状态，改变行为 
 */ 
public class Test { 
  public static void main(String[] args) { 
    /* 
     * 本例的 状态值只有两个，由状态类自身控制 
     * 也可以把状态值的控制，交由客户端来设置 
     */ 
    WindowContext context = new WindowContext(new WindowState("窗口")); 
    context.switchState(); 
    context.switchState(); 
    context.switchState(); 
    context.switchState(); 
 
  } 
} 

切换为窗口状态 
切换为全屏状态 
切换为窗口状态 
切换为全屏状态 

/** 
 * 商品促销 
 * 本类为：收取现金的类 
 */ 
public interface ICashSuper { 
   double acceptCash(double money); 
} 

/** 
 * 正常收取现金 
 * @author stone 
 * 
 */ 
public class CashNormal implements ICashSuper { 
 
  @Override 
  public double acceptCash(double money) { 
    return money; 
  } 
 
} 

/** 
 * 打折收取现金 
 * @author stone 
 * 
 */ 
public class CashRebate implements ICashSuper { 
  private double rebate; //折扣 
  public CashRebate (double rebate) { 
    this.rebate = rebate; 
  } 
 
  @Override 
  public double acceptCash(double money) { 
    return new BigDecimal(money * rebate / 10).setScale(2, BigDecimal.ROUND_HALF_UP).doubleValue(); 
  } 
   
   
} 

/** 
 * 让利返现 收取现金 
 * @author stone 
 * 
 */ 
public class CashReturn implements ICashSuper { 
  private double moneyCondition; //返现底限金额 
  private double returnMoney; //返还金额 
  public CashReturn(double moneyCondition, double returnMoney) { 
    this.moneyCondition = moneyCondition; 
    this.returnMoney = returnMoney; 
  } 
 
  @Override 
  public double acceptCash(double money) {//多重返利 
    if (money >= moneyCondition) { 
      return money - Math.floor(money / moneyCondition) * returnMoney; 
    } else { 
      return money; 
    } 
  } 
   
   
} 

/** 
 * 根据传递的的策略类，执行相应的行为 
 */ 
public class CashContext { 
  private ICashSuper casher; 
   
  public CashContext() { 
     
  } 
   
  public CashContext(ICashSuper casher) { 
    this.casher = casher; 
  } 
   
  public void setCasher(ICashSuper casher) { 
    this.casher = casher; 
  } 
   
  //根据具体的策略对象，调用它的算法行为 
  public double acceptCash(double money) { 
    return this.casher.acceptCash(money); 
  } 
   
} 

public class Test { 
  public static void main(String[] args) { 
    double money = 998; //原价 
    CashContext cashContext = new CashContext(new CashNormal()); 
    System.out.println("原价：" + cashContext.acceptCash(money)); //通常 策略 
     
    cashContext.setCasher(new CashRebate(8.5)); 
    System.out.println("打85折：" + cashContext.acceptCash(money)); //折扣  策略  85折 
     
    cashContext.setCasher(new CashReturn(300, 50)); 
    System.out.println("满300 返50：" + cashContext.acceptCash(money)); //返现 策略  满300 返50 
     
  } 
} 

原价：998.0 
打85折：848.3 
满300 返50：848.0