状态模式

状态模式允许一个对象在其内部状态改变的时候改变其行为。这个对象看上去就像是改变了它的类一样。状态模式由抽象状态类（定义状态方法），具体状态类（实现具体的状态方法，改变内部状态，同时按条件改变和状态管理类的状态对象）和状态管理类(存储状态类对象)组成，比如人的一生，在各个阶段的状态，随着年龄增长而改变。

示例：

public class State {
    public static void main(String[] args){
        State state=new State();
        StateManager stateManager=state.new StateManager();
        stateManager.setState(state.new Child());
    }

    abstract class PersonState{
        protected int startAge,endAge;

        public PersonState(int startAge,int endAge) {
            this.startAge = startAge;
            this.endAge = endAge;
        }

        abstract void grow(StateManager manager);

        abstract void feature();
    }

    class Child extends PersonState{
        public Child() {
            super(0, 6);
        }

        @Override
        void grow(StateManager manager) {
            while (true) {
                startAge++;
                if (startAge > endAge) {
                    manager.setState(new Student());
                    break;
                }
                feature();
            }
        }

        @Override
        void feature() {
            System.out.println("我是个小屁孩，现在"+startAge+"岁，玩就是了");
        }
    }

    class Student extends PersonState{
        public Student() {
            super(7,22);
        }

        @Override
        void grow(StateManager manager) {
            while (true) {
                startAge++;
                if (startAge > endAge) {
                    manager.setState(new Adult());
                    break;
                }
                feature();
            }
        }

        @Override
        void feature() {
            System.out.println("我是个学生，现在"+startAge+"岁，学得头都大了");
        }
    }

    class Adult extends PersonState{
        public Adult() {
            super(23, 40);
        }

        @Override
        void grow(StateManager manager) {
            while (true) {
                startAge++;
                if (startAge > endAge) {
                    manager.setState(new Middle());
                    break;
                }
                feature();
            }
        }

        @Override
        void feature() {
            System.out.println("我是个加班狗，现在"+startAge+"岁，没钱没时间，苦逼");
        }
    }

    class Middle extends PersonState{
        public Middle() {
            super(41, 60);
        }

        @Override
        void grow(StateManager manager) {
            while (true) {
                startAge++;
                if (startAge > endAge) {
                    manager.setState(new Elderly());
                    break;
                }
                feature();
            }
        }

        @Override
        void feature() {
            System.out.println("我是个中年人，现在"+startAge+"岁，有点钱了，压力还是大啊");
        }
    }

    class Elderly extends PersonState{
        public Elderly() {
            super(61, 100);
        }

        @Override
        void grow(StateManager manager) {
            while (true) {
                startAge++;
                if (startAge > endAge) {
                    System.out.println("死啦死啦，活够了");
                    break;
                }
                feature();
            }
        }

        @Override
        void feature() {
            System.out.println("我是个老年人，现在"+startAge+"岁，遛遛狗，下下棋，等死");
        }
    }

    class StateManager{
        private PersonState state;

        public void setState(PersonState state) {
            this.state = state;
            this.state.feature();
            this.state.grow(this);
        }
    }
}