Operator precedence in Java - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is operator precedence in Java?

Operator precedence determines the order in which operators are evaluated in an expression. Operators with higher precedence are evaluated before those with lower precedence.

beginner

Which operator has higher precedence: multiplication (*) or addition (+)?

Multiplication (*) has higher precedence than addition (+), so it is evaluated first in an expression.

beginner

How does parentheses affect operator precedence?

Parentheses have the highest precedence and force the expression inside them to be evaluated first, regardless of other operators.

intermediate

What is the precedence order between logical AND (&&) and logical OR (||)?

Logical AND (&&) has higher precedence than logical OR (||), so && operations are evaluated before || operations.

intermediate

In the expression: int result = 3 + 4 * 2 / (1 - 5); which operation is evaluated first?

The expression inside parentheses (1 - 5) is evaluated first because parentheses have the highest precedence.

Which operator is evaluated first in the expression: 5 + 3 * 2?

A Addition (+)

B Multiplication (*)

C Both at the same time

D Depends on variable types

Multiplication (*) has higher precedence than addition (+), so it is evaluated first.

What does parentheses do in an expression?

A They lower the precedence of operators inside

B They have no effect on operator precedence

C They force the expression inside to be evaluated first

D They change operators to functions

Parentheses have the highest precedence and force the expression inside to be evaluated first.

Which operator has higher precedence: logical AND (&&) or logical OR (||)?

A Logical AND (&&)

B They have the same precedence

C Logical OR (||)

D Depends on the expression

Logical AND (&&) has higher precedence than logical OR (||).

In the expression: 10 / 2 * 3, which operation is performed first?

A Division (10 / 2)

B Multiplication (2 * 3)

C Both at the same time

D Depends on parentheses

Division and multiplication have the same precedence and are evaluated left to right, so division is first.

What is the result of: 4 + 2 * 3 - 1?

A 11

B 15

C 7

D 9

Multiplication first: 2 * 3 = 6; then addition and subtraction left to right: 4 + 6 = 10; 10 - 1 = 9.

Explain how operator precedence affects the evaluation of the expression: 8 + 4 * 2.

Think about which operator Java calculates first.

Describe the role of parentheses in changing the order of operations in Java expressions.

Consider how parentheses can change the normal calculation order.

Practice

1. Which operator has the highest precedence in the expression 3 + 4 * 5?

easy

A. Subtraction (-)

B. Addition (+)

C. Division (/)

D. Multiplication (*)

Solution

1. Step 1: Identify operators in the expression

   The expression has addition (+) and multiplication (*).

2. Step 2: Recall operator precedence rules

   Multiplication (*) has higher precedence than addition (+), so it runs first.

3. Final Answer:

   Multiplication (*) -> Option D

4. Quick Check:

   Multiplication > Addition [OK]

Hint: Multiplication and division run before addition and subtraction [OK]

Common Mistakes:

• Thinking addition runs before multiplication
• Ignoring operator precedence
• Assuming left to right always applies

2. Which of the following expressions is syntactically correct in Java?

easy

A. int result = 5 + (3 * 2);

B. int result = 5 + * 3;

C. int result = 5 + 3 *;

D. int result = 5 + 3 * 2))

Solution

1. Step 1: Check each expression for syntax errors

   int result = 5 + * 3; has an invalid operator sequence '+ *'. int result = 5 + 3 *; ends with '*;' which is incomplete. int result = 5 + 3 * 2)) has unmatched parentheses.

2. Step 2: Validate correct syntax

   int result = 5 + (3 * 2); uses parentheses properly and valid operators, so it is correct.

3. Final Answer:

   int result = 5 + (3 * 2); -> Option A

4. Quick Check:

   Valid syntax uses proper operators and balanced parentheses [OK]

Hint: Check for balanced parentheses and valid operator placement [OK]

Common Mistakes:

• Leaving operators without operands
• Unbalanced parentheses
• Using invalid operator sequences

3. What is the output of the following Java code?

int x = 2 + 3 * 4 - 6 / 2;
System.out.println(x);

medium

A. 12

B. 10

C. 11

D. 14

Solution

1. Step 1: Apply operator precedence to the expression

   Multiplication and division run before addition and subtraction:
   3 * 4 = 12
   6 / 2 = 3

2. Step 2: Calculate the expression left to right

   Expression becomes: 2 + 12 - 3
   2 + 12 = 14
   14 - 3 = 11

3. Final Answer:

   11 -> Option C

4. Quick Check:

   2 + (3*4) - (6/2) = 11 [OK]

Hint: Do multiplication/division first, then addition/subtraction [OK]

Common Mistakes:

• Adding before multiplying
• Ignoring division precedence
• Calculating left to right without precedence

4. The following code throws a compilation error. What is the cause?

int a = 5;
int b = 10;
int c = a + * b;

medium

A. Incorrect variable declaration

B. Missing operand between + and * operators

C. Missing semicolon at the end

D. Using undeclared variable

Solution

1. Step 1: Analyze the expression syntax

   The expression 'a + * b' has two operators '+' and '*' without a number or variable between them, which is invalid.

2. Step 2: Identify the compilation error cause

   Java expects an operand between operators. The missing operand causes a syntax error.

3. Final Answer:

   Missing operand between + and * operators -> Option B

4. Quick Check:

   Operators must have operands between them [OK]

Hint: Check for missing operands between operators [OK]

Common Mistakes:

• Assuming multiple operators can be together
• Ignoring syntax errors
• Confusing variable declaration with expression errors

5. Consider the expression:

int result = 10 - 2 * 3 + 4 / 2;

How can you change the expression using parentheses to make addition happen before multiplication and subtraction?

hard

A. int result = 10 - (2 * (3 + 4 / 2));

B. int result = (10 - 2) * (3 + 4) / 2;

C. int result = 10 - ((2 * 3) + (4 / 2));

D. int result = 10 - (2 * 3 + 4) / 2;

Solution

1. Step 1: Understand original precedence

   Original expression evaluates multiplication and division first:
   2 * 3 = 6
   4 / 2 = 2
   Then subtraction and addition left to right:
   10 - 6 + 2 = 6

2. Step 2: Use parentheses to make addition happen before multiplication and subtraction

   To add before multiplication, group inside parentheses:
   3 + 4 / 2
   Since division has higher precedence, 4 / 2 = 2, so 3 + 2 = 5
   Expression becomes:
   10 - (2 * 5) = 10 - 10 = 0

3. Final Answer:

   int result = 10 - (2 * (3 + 4 / 2)); -> Option A

4. Quick Check:

   Parentheses change order to add before multiply [OK]

Hint: Use parentheses to group operations you want first [OK]

Common Mistakes:

• Misplacing parentheses changing meaning
• Ignoring division precedence inside parentheses
• Assuming parentheses don't affect order