State Manager Java sample

StateManager.java

import java.util.function.Consumer;

public class StateManager {
    Consumer<Boolean> m_curfunc;
    Consumer<Boolean> m_nextfunc;

    public void Goto(Consumer<Boolean> func) {
        m_nextfunc = func;
    }

    public void Update() {
        Boolean bFirst = false;
        if (m_nextfunc != null) {
            m_curfunc = m_nextfunc;
            m_nextfunc = null;
            bFirst = true;
        }
        if (m_curfunc!=null) {
            m_curfunc.accept(bFirst);
        }
    }

    public Boolean CheckState(Consumer<Boolean> func) {
        return (m_curfunc == func);
    }
}

Sub.java

import java.util.function.Consumer;

class Sub extends StateManager {

    Consumer<Boolean> S_START=(bFirst)->{
        if (bFirst) {
            System.out.println("Into S_START");
        }
        this.Goto(this.S_0001);
    };
    Consumer<Boolean> S_0001=(bFirst)->{
        if (bFirst) {
            System.out.println("Into S_0001");
        }
        this.Goto(this.S_END);
    };
    Consumer<Boolean> S_END=(bFirst)->{
        if (bFirst) {
            System.out.println("Into S_END");
        }
    };
    
    public void Start()
    {
        this.Goto(this.S_START);
    }
    
    public Boolean IsEnd()
    {
        return this.CheckState(this.S_END);
    }
}

Test.java

public class Test {
    public static void main(String[] args) {

        System.out.println("Hello!");

        Sub sm = new Sub();
        sm.Start();

        while(!sm.IsEnd()){
            sm.Update();
        }

        System.out.println("Bye!");
    }
}