feat: 新增并发型状态机(基于CAS实现, 未完成).

src/main/java/com/serliunx/statemanagement/manager/AbstractStateManager.java

@@ -100,6 +100,11 @@ public abstract class AbstractStateManager<S> implements StateManager<S> {
 		}
 	}
 
+	@Override
+	public int size() {
+		return stateList.size();
+	}
+
 	@Override
 	public boolean isSwitchable() {
 		return stateList.size() > 1;
@@ -140,6 +145,16 @@ public abstract class AbstractStateManager<S> implements StateManager<S> {
 		return stateList.get(index);
 	}
 
+	/**
+	 * 获取指定下标的状态
+	 *
+	 * @param index	下标
+	 * @return 状态
+	 */
+	protected S get(int index) {
+		return stateList.get(index);
+	}
+
 	/**
 	 * 获取指定状态在状态列表中的序号
 	 *