What’s New in Alibaba’s Java Manual? 3 Key Coding Standards Revealed

The "Java Development Manual" is a collective effort of Alibaba's technical team, refined through extensive real‑world practice and open‑sourced for community collaboration.

On April 22, the "Taishan" edition was launched, highlighting three major additions: five new date‑time conventions, two table‑alias SQL conventions, and a unified error‑code convention.

Date‑Time Conventions

Seven new rules were added, the first five are mandatory:

Use lowercase y for the year in date patterns; yyyy represents the calendar year, while uppercase YYYY denotes the week‑year.

Distinguish uppercase M (month) from lowercase m (minute); uppercase H (24‑hour) from lowercase h (12‑hour).

Obtain the current milliseconds with System.currentTimeMillis() instead of new Date().getTime().

Avoid using java.sql.Date, java.sql.Time, or java.sql.Timestamp anywhere in the code.

Do not hard‑code a year as 365 days; account for leap years.

The remaining two are recommended:

Avoid February 29 in non‑leap‑year schedules; use a cron expression like 0 0 0 28 2 ? for yearly tasks.

Use enum values for months; remember that Calendar months are zero‑based (January = 0).

Table‑Alias SQL Conventions

Mandatory: When a query or modification involves multiple tables, prefix column names with the table alias or name to avoid ambiguous column errors.

Recommended: Add AS before aliases and name them sequentially as t1, t2, … for clarity.

Unified Error‑Code Convention

A new section defines standardized error codes for each system, improving API readability and enabling real‑time monitoring of exception occurrences.