import java.time.YearMonth;
import java.time.format.DateTimeFormatter;
import java.time.format.DateTimeFormatterBuilder;
import java.util.Locale;
 
public class Main {
	public static void main(String[] args) {
		DateTimeFormatter dtf = new DateTimeFormatterBuilder()
								.parseCaseInsensitive()
								.appendPattern("MMM/uuuu")
								.toFormatter(Locale.ROOT);
 
		String currentMonth = "SEP/2021";
 
		YearMonth currentYm = YearMonth.parse(currentMonth, dtf);
		YearMonth previousYm = currentYm.minusMonths(1);
 
		String previousMonth = previousYm.format(dtf);
		System.out.println(previousMonth);
 
		// If required, convert it into the UPPER CASE
		System.out.println(previousMonth.toUpperCase());
	}
}

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