class DecToBin{
    public static void main(String[] args){
    int dec = 64;
    int bin=0,rem=0;
    while(dec!=0){
        rem=dec%2;
        bin=bin*10+rem;
        dec=dec/2;
    }
    System.out.println("In Binary = "+bin);
  }
}

String s="";
while(dec!=0)
{
    rem=dec%2;
    s=(Integer.toString(rem)).concat(s);
    dec=dec/2;
}
System.out.println("In Binary = "+s);

Integer.toString() //converts an integer to a string
concat is used to add to strings.

int binary_number=Integer.parseInt(s);