03 — Operators & Casting

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▶️ java pkg1core/core4Operators.java

Arithmetic operators

1int a = 7, b = 2;2System.out.println(a / b);   // 3  (not 3.5)3System.out.println(a % b);   // 14System.out.println(7 / 2.0); // 3.5 (double division)

⚠️ Integer division truncates — 7 / 2 is 3, not 3.5.

Assignment & compound operators

1int x = 10;2x += 5;    // x = x + 5  → 153x *= 2;    // x = x * 2  → 304x++;       // post-increment: use then add 15++x;       // pre-increment: add 1 then use

Comparison operators

Return boolean: == != < > <= >=

1int i = 0;2System.out.println(i++ + ++i);  // 0 + 2 = 2 (tricky — trace on paper!)

💡 Use == for primitives; use .equals() for objects (especially String).

Logical operators

Short-circuit: false && anything never evaluates anything.

1if (list != null && !list.isEmpty()) { ... }  // safe — null check first

Bitwise operators

| & ^ ~ << >> >>> — operate on individual bits. Used in flags, permissions, low-level math.

1System.out.println(5 & 3);   // 1  (0101 & 0011 = 0001)2System.out.println(5 | 3);   // 73System.out.println(~1);      // -2 (two's complement)

Ternary operator

1String grade = (score >= 60) ? "Pass" : "Fail";

Shorthand for simple if/else assignment.

Operator precedence (highest first)

1. () grouping
2. ++ -- ! ~
3. * / %
4. + -
5. < > <= >=
6. == !=
7. &&
8. ||
9. ?: ternary
10. = assignment

When in doubt, use parentheses.

Casting recap

Practice

1. Run core4Operators.
2. Predict output of i++ + ++i before running.
3. Write a ternary that picks the larger of two ints.

Next → 04 Control Flow Related → 01 Core Java