>>66
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Q66 {
public static void main(String[] args) throws IOException {
System.out.println("整数を入力してください");
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
int number = Integer.parseInt(br.readLine());
System.out.println(toBinaryString(number));
}

public static String toBinaryString(int i) {
return i == 0 ? "0" : toBinaryString(new StringBuilder(32), i).toString();
}

private static StringBuilder toBinaryString(StringBuilder dst, int i) {
return i == 0 ? dst : toBinaryString(dst, i >>> 1).append(i & 1);
}
}

>>67
http://pc8.2ch.net/test/read.cgi/tech/1112154540/863
のだと0以下の場合駄目じゃない？