acl/src/main/java/org/springframework/security/acls/domain/AclFormattingUtils.java
public static String printBinary(int mask, char code) {
		Assert.doesNotContain(Character.toString(code),
				Character.toString(Permission.RESERVED_ON),
				() -> Permission.RESERVED_ON + " is a reserved character code");
		Assert.doesNotContain(Character.toString(code),
				Character.toString(Permission.RESERVED_OFF),
				() -> Permission.RESERVED_OFF + " is a reserved character code");

		return printBinary(mask, Permission.RESERVED_ON, Permission.RESERVED_OFF)
				.replace(Permission.RESERVED_ON, code);
	}
public static String printBinary(int mask, char code) {
		Assert.doesNotContain(Character.toString(code),
				Character.toString(Permission.RESERVED_ON),
				() -> Permission.RESERVED_ON + " is a reserved character code");
		Assert.doesNotContain(Character.toString(code),
				Character.toString(Permission.RESERVED_OFF),
				() -> Permission.RESERVED_OFF + " is a reserved character code");

		return printBinary(mask, Permission.RESERVED_ON, Permission.RESERVED_OFF)
				.replace(Permission.RESERVED_ON, code);
	}
Returns a representation of the active bits in the presented mask, with each active
bit being denoted by the passed character.
<p>
Inactive bits will be denoted by character {@link Permission#RESERVED_OFF}.

@param mask the integer bit mask to print the active bits for
@param code the character to print when an active bit is detected

@return a 32-character representation of the bit mask