数字全排列 java深度优先搜索

import java.util.Scanner;
import java.util.ArrayList;
public class Quanpailie{
    
    public int a[] ;
    public int book[] ;
    public int n;
    public int step=1;
    public static void main(String[] args) {
        Quanpailie he=new Quanpailie();
        he.go();
        //深度搜索;
    }
    public void setup(int step){
        for(int i=1;i<=n;i++){
            if(step==n+1){
                look(a);
                break;
            }else{
                if(book[i]==0){
                    a[step]=i;
                    book[i]=1;
                    setup(step+1);
                    book[i]=0;
                }
            }
        }
    }
    public void look(int[] list){
        System.out.println("");
        for(int i=1;i<list.length;i++){
            System.out.print(list[i]);
        }
    }

    public void go(){
        Scanner sc=new Scanner(System.in);
        n=sc.nextInt();
        a=new int[n+1];
        book=new int[n+1];
        setup(1);
    }
    
}