what's wrong with my 'Josephus Problem' program?

Hey guys, good to see you, I'm a beginner of English and Java, so, I'm trying best to make myself clear...































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































This's the original 'Josephus Problem' program, looks some troubles with it which gave me a WRONG answer, although it's totally OK if the 'Length' is much more short...I tried '5''6''10', it's alright.































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































anyone can tell me where is the bug?































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































THANK YOU A LOT!

Java Code:

public class Josefu
{
        public static void main(String[] args)
        {
                Cycle cy=new Cycle();
        cy.setLen(41);
                cy.setPosi(1);
                cy.setJump(3);
                cy.creatCycle();
                cy.play();
                
        }
}
//
class Child
{
        int no;
        Child nextChild=null;
        Child prevChild=null;
    public Child(int no)
        {
                this.no=no;
        }
}
//
class Cycle
{
        int posi=0;
        int jump=0;
        int len=0;
        Child firstChild=null;
        Child fwdChild=null;
        Child bwdChild=null;
        public void setPosi(int posi)
        {
                this.posi=posi;
        }
        public void setJump(int jump)
        {
                this.jump=jump;
        }
        public void setLen(int len)
        {
                this.len=len;
        }
        //
        public void creatCycle()
        {
                for(int i=1;i<=len;i++)
                {
                        if(i==1)
                        {
                                Child cd=new Child(i);
                                this.firstChild=cd;
                                this.fwdChild=cd;
                                this.bwdChild=cd;
                        }
                        else 
                        {
                                if(i==len)
                                {
                                        Child cd=new Child(i);
                                        fwdChild.nextChild=cd;
                                        fwdChild=cd;
                                        fwdChild.prevChild=bwdChild;
                                        bwdChild=fwdChild;
                                        fwdChild.nextChild=this.firstChild;
                                        this.firstChild.prevChild=bwdChild;
                                        
                                }
                                else
                                {
                                   Child cd=new Child(i);
                                   fwdChild.nextChild=cd;
                                   fwdChild=cd;
                                   fwdChild.prevChild=bwdChild;
                                   bwdChild=fwdChild;
                                }
                        }
                }
        }
        public void play()
        {
                Child fwdChild=this.firstChild;
        //
                for(int p=1;p<posi;p++)
                {
                        fwdChild=fwdChild.nextChild;
                }
        while(len!=1)
                {
                        for(int j=1;j<jump;j++)
                    {
                          fwdChild=fwdChild.nextChild;
                    }
                    //
                        System.out.println(fwdChild.no);
                    fwdChild.prevChild.nextChild=fwdChild.nextChild;
                    fwdChild=fwdChild.nextChild;
                    this.len--;
                }
                //
                System.out.println(fwdChild.no);
        }
}