Java Operators and Expressions Study Notes

Arithmetic Operators

• Perform mathematical operations on operands:

  • Addition ($+$): Adds operands ($x = y + z$).

  • Subtraction ($-$): Subtracts right operand from left operand ($x = y - z$).

  • Multiplication ($*$): Multiplies operands ($x = y * 3$).

  • Division ($/$): Divides left operand by right operand ($x = y / z$).

  • Modulus ($\%$): Calculates remainder of integer division ($x = y \% z$).

• Primitive numeric operations automatically convert calculations to $\text{int}$ if exceeding the byte range of $-128$ to $+127$.

• Joining string operands with $+$ concatenates them into a single string (e.g., $2 + \text{"abc"} = \text{"2abc"}$).

Assignment Operators

• Assign values, variables, or functions to variables:

  • Simple assignment ($=$): Assigns right operand value to left operand ($x = y$).

  • Compound assignments: $+=$, $-=$, $*=$, $/=$, $\%=$ (e.g., $x += y$ is equivalent to $x = x + y$).

• Allows simultaneous assignment to multiple variables (e.g., $x = y = 0$).

Unary Operators

• Require a single operand to execute operations:

  • Unary Plus ($+$) and Unary Minus ($-$): Represent positive ($+a$) or negative ($-a$) values.

  • Increment ($++$) and Decrement ($--$): Increase or decrease operand value by $1$.

  • Pre-increment/decrement (e.g., $++invar$): Modifies value prior to evaluation (e.g., if $x = 7$, $++x$ becomes $8$).

  • Post-increment/decrement (e.g., $invar--$): Modifies value after evaluation (e.g., if $x = 12$, $x--$ becomes $11$).

  • Logical Complement ($!$): Inverts a Boolean value (e.g., $!\text{true}$).

Comparison Operators

• Relational operators evaluate conditions between values and return Boolean outputs:

  • Equal to ($==$) and Not Equal to ($!=$)

  • Greater Than ($>$) and Less Than ($<$)

  • Greater Than or Equal to ($>=$) and Less Than or Equal to ($<=$)

Shift Operators

• Shift bit patterns of integer data types using zeros ($0$) as fillers:

  • Right Shift ($>>$): Shifts bits right by specified second operand value (e.g., $9 >> 2 = 2$).

  • Left Shift ($<<$): Shifts bits left, filling zeros on the right (e.g., $9 << 2 = 36$).

  • Right Unsigned Shift ($>>>$): Shifts bits right and replaces shifted bits with $0$ (e.g., $-10 >>> 3$).

Bitwise Operators

• Perform bit-by-bit operations on $\text{byte}$, $\text{short}$, $\text{int}$, $\text{long}$, and $\text{char}$ data types:

  • AND ($\&$): Yields $1$ if both bits are $1$, otherwise $0$.

  • OR ($|$): Yields $0$ if both bits are $0$, otherwise $1$.

  • XOR (\text{^}): Yields $0$ if bits are identical, $1$ if different.

  • Inversion ($\sim$): Converts all $1$ bits to $0$ and $0$ bits to $1$.

Logical Operators

• Combine outcomes of Boolean expressions:

  • Logical AND ($\&\&$): Returns $\text{true}$ if both operands are non-zero/true; otherwise returns $\text{false}$.

  • Logical OR ($||$): Returns $\text{true}$ if at least one operand is non-zero/true; otherwise returns $\text{false}$.

Conditional Operator

• Ternary Operator ($\text{condition} ? \text{val1} : \text{val2}$): Evaluates $\text{val1}$ if condition returns true, otherwise evaluates $\text{val2}$ (e.g., $x = (y > z) ? y : z$).

Order of Precedence

• Hierarchy defining execution order from highest to lowest precedence:

  1. High Precedence: $[]$, $()$

  2. Unary: $+$, $-$, $\sim$, $!$, $++$, $--$

  3. Multiplicative: $*$, $/$, $\%$

  4. Additive: $+$, $-$

  5. Shift: $<<$, $>>$, $>>>$

  6. Relational: $<$, $<=$, $>=$, $>$

  7. Equality: $==$, $!=$

  8. Bitwise: $\&$, \text{^}, $|$

  9. Logical: $\&\&$, $||$

  10. Conditional: $?:$

  11. Assignment: $=$, $+=$, $-=$, $*=$, $/=$, $\%=$

Expressions in Java

• Combination of variables, constants, literals, and operators evaluated to produce a single value, ending with a semicolon (;).

• Types of Expressions:

  • Arithmetic Expression: Returns a numeric value based on operators and operands (e.g., $int\ z = x + y$).

  • Assignment Expression: Assigns a value to a variable (e.g., $a = a + 4$).

  • Relational Expression: Compares values using relational operators (e.g., $boolean\ result = x < y$).

  • Logical Expression: Evaluates multiple conditions with logical operators (e.g., $boolean\ result = (j < k) \&\& (k < 4)$).

  • Conditional Expression: Uses the ternary operator to assign values based on evaluated conditions (e.g., $int\ n = (l < m) ? 2 : 3$).