private String getNextStepId(String prefix) {
			if (!allocatedStepIds.contains(prefix)) {
				// Avoid number suffix for the first one
				allocatedStepIds.add(prefix);
				return prefix;
			}
			int suffix = 1;
			String proposal = null;
			do {
				proposal = new StringBuilder(prefix).append(Integer.toString(suffix++)).toString();
			}
			while (allocatedStepIds.contains(proposal));
			allocatedStepIds.add(proposal);
			return proposal;
		}
Determine the next unique ID we can use for an XML element.
spring-xd-dirt/src/main/java/org/springframework/xd/dirt/job/dsl/JobSpecification.java