Every way to build text

+ concatenation, printf and String.format, text blocks, String.join and StringBuilder: which fits which job.

A few pieces, once → +. Watch the order: "Total: " + a + b joins, a + b + " items" adds first.
Numbers in columns, a fixed number of decimals → String.format / printf with format specifiers such as %8.2f.
Several lines of fixed text (JSON, SQL, a help message) → a text block """.
A list joined with a separator → String.join(", ", names).
Text built up in a loop → StringBuilder; += in a loop copies the whole string every pass.

Joining

Section

Output and formatting

println, + and printf.

Rule

Precedence first, then left to right

Operators, precedence and scope →

Formal. In a Java expression, *, / and % bind tighter than binary + and -, which bind tighter than the comparisons, which bind tighter than &&, which binds tighter than ||. Operators of the same precedence group left to right, except assignment, which groups right to left. Operands are evaluated left to right, and && and || evaluate their right operand only when the left one doesn't already decide the result.

In plain English. Do multiplication, division and remainder before adding and subtracting, then work from the left, just as in school arithmetic. Brackets override everything, so when in doubt, add them.

Example. 2 + 3 * 4 is 14, 20 - 5 - 3 is 12, and 24 / 4 / 2 is 3. "Total: " + 2 + 3 is "Total: 23" because the left + meets a String first, while 2 + 3 + " items" is "5 items".

Why this rule exists. A fixed, familiar order lets everyone read the same expression the same way, without brackets around every step.

Why + joins or adds depending on what came first.

Section