java 设计模式之State(状态模式）

//状态类 
public interface State { 
  public void doAction(Context context); 
} 
//实现类StartState.java 
public class StartState implements State { 
  public void doAction(Context context) { 
   System.out.println("Player is in start state"); 
   context.setState(this);  
  } 
  public String toString(){ 
   return "Start State"; 
  } 
} 
//实现StopState.java 
public class StopState implements State { 
  public void doAction(Context context) { 
   System.out.println("Player is in stop state"); 
   context.setState(this);  
  } 
  public String toString(){ 
   return "Stop State"; 
  } 
} 
 
//上下文Context.java 实际运用时可自行更改 
public class Context { 
  private State state; 
  public Context(){ 
   state = null; 
  } 
  public void setState(State state){ 
   this.state = state;         
  } 
  public State getState(){ 
   return state; 
  } 
} 
 
//测试类 
public class StatePatternDemo { 
  public static void main(String[] args) { 
   Context context = new Context(); 
   StartState startState = new StartState(); 
   startState.doAction(context); 
   System.out.println(context.getState().toString()); 
  
   StopState stopState = new StopState(); 
   stopState.doAction(context); 
  
   System.out.println(context.getState().toString()); 
  } 
} 

Player is in start state

Start State

Player is in stop state

Stop State