This article presents fifteen practical Java backend coding guidelines—including avoiding "where 1=1" in MyBatis, iterating Map entrySet, using Collection.isEmpty, pre‑sizing collections, employing StringBuilder, preferring Set for contains checks, initializing static members correctly, removing dead code, shielding utility constructors, eliminating redundant catches, using String.valueOf, avoiding BigDecimal(double), returning empty collections, calling equals on constants, securing enum fields, and escaping regex in split—each illustrated with bad and good code examples to improve readability, safety, and efficiency.