Program to print Binary Numbers where adjacent bits are not 1 [Java]

This was the interview question asked to my teacher when she attend an interview.
I have created a Java program to demonstrate it.

Eg.
1010 - Valid.
1101 - Not Valid because two 1's are in adjacent  positions.

/* # ##### ### ######## ### ### TM # # # # # # # # # # # # # # # # # # # # # ####### ####### # # # # # # # # # # # # # ### ### #### ### ### ### ### (C) AJITH KP (C) */ import java.util.*; public class BinaryX { public static void main(String[] args) { String bin; int n, i, j, k, flag; char[] bn; Scanner sc = new Scanner(System.in); StringBuilder bld; System.out.print("Enter Digit: "); n = sc.nextInt(); if(n==1) { for(i=0;i<2;i++) { flag = 0; bin = binary(i); bld = new StringBuilder(bin); bn = bin.toCharArray(); for(j=0;j<bn.length-1;j++) { if(bn[j]==bn[j+1]&&bn[j]=='1') { flag = 1; } } if(flag==0) { System.out.println(i+" : "+bld.reverse()); } } } else { //System.out.println(square(n-1)+" : "+square(n)); for(i=_2rised(n-1);i<_2rised(n);i++) { flag = 0; bin = binary(i); bld = new StringBuilder(bin); bn = bin.toCharArray(); for(j=0;j<bn.length-1;j++) { if(bn[j]==bn[j+1]&&bn[j]==49) { flag = 1; //System.out.print("Found"); } } if(flag==0) { System.out.println(i+" : "+bld.reverse()); } } } } static int _2rised(int n) { return 2<<(n-1); } static String binary(int n) { String bx = ""; if(n==0) { return("0"); } for(int y=0;n!=0;y++) { bx+=(n%2); n/=2; } return bx; } }