Language Fundamentals

Operators & Expressions

Java's operators mostly follow C conventions — with well-defined evaluation order, integer division that truncates toward zero, short-circuit logical operators, and a distinct unsigned right shift.

Integer / truncates toward zero; % can be negative — use Math.floorMod for cyclic indexing
&& and || short-circuit; & and | always evaluate both sides
>> keeps the sign bit (arithmetic shift); >>> fills with zeros (logical shift)
Operands are evaluated left to right, and mixed-type arithmetic promotes to the wider type
The conditional operator cond ? a : b is an expression — use it for simple selections

Arithmetic (+ - * / %), comparison (== != < <= > >=), logical (&& || !), bitwise (& | ^ ~), shifts (<< >> >>>), assignment and compound assignment (+= etc.), increment/decrement (++ --), and the ternary conditional. Precedence follows C; when in doubt, parenthesize — the reader benefits even when the compiler doesn't need it.

Truncation, remainder, floorMod

System.out.println(15 / 2);              // 7
System.out.println(15 % 2);              // 1
System.out.println(-7 % 3);              // -1 (sign follows dividend)
System.out.println(Math.floorMod(-7, 3)); // 2
System.out.println(1.0 / 0);             // Infinity (no exception!)

NaN (not-a-number) results from 0.0/0 or Math.sqrt(-1). No `NaN` is equal to anything, including itself — test with Double.isNaN(x), never x == Double.NaN.

Short-circuit evaluation

&& and || evaluate the right operand only when needed — the idiomatic guard if (list != null && !list.isEmpty()) depends on it. The single-character forms & and | on booleans always evaluate both sides; on integers they are bitwise operations.

Bit manipulation

Shifts and masks

int flags = 0b0110;
boolean third = (flags & 0b0100) != 0;  // test a bit
flags |= 0b0001;                        // set a bit
flags &= ~0b0010;                       // clear a bit

System.out.println(-8 >> 1);   // -4  (sign-extends)
System.out.println(-8 >>> 1);  // 2147483644 (zero-fills)