'What is the quickest way to print Binary permutation?

If n=3 and r=2, print below

110
101
011

I'm using below code, But it takes a long time.

public void printBinaryPermutation(int n, int r)
{
    for(BigInteger i = new BigInteger("0"); i.compareTo(BigInteger.TWO.pow(n)) == -1; i = i.add(BigInteger.ONE))
    {
        String str = i.toString(2);
        while(str.length() < n)
        {
            str = "0" + str;
        }
        BigInteger amount = new BigInteger("0");
        for(char c : str.toCharArray())
        {
            if(c == '1')
            {
                amount = amount.add(BigInteger.ONE);
            }
        }
        if(amount.compareTo(new BigInteger(String.valueOf(r))) == 0)
        {
            System.out.println(str);
        }
    }
}

What is the quickest way to print Binary permutation?

javabinarypermutationrfor-loopfilter


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