Operator precedence in Java - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Java code involving mixed operators?

Consider the following Java code snippet:

int result = 3 + 4 * 2 / (1 - 5) % 2;

What is the value of result after this code runs?

Java

int result = 3 + 4 * 2 / (1 - 5) % 2;
System.out.println(result);

A 1

B 3

C 0

D -1

💡 Hint

Remember the order: parentheses, multiplication/division/modulus, then addition/subtraction.

Step by step:
Parentheses: (1 - 5) = -4
4 * 2 = 8
8 / -4 = -2 (integer division)
-2 % 2 = 0
3 + 0 = 3

❓ Predict Output

intermediate

What is the output of this Java expression with logical and bitwise operators?

Given the code:

int a = 5; // binary 0101
int b = 3; // binary 0011
boolean result = a > 2 && b < 5 | a == 5;

What is the value of result?

Java

int a = 5;
int b = 3;
boolean result = a > 2 && b < 5 | a == 5;
System.out.println(result);

A true

B false

C Compilation error

D Runtime exception

💡 Hint

Check operator precedence between && and | in Java.

Operator precedence: && has higher precedence than | (bitwise OR).
So expression is evaluated as: (a > 2 && b < 5) | a == 5
a > 2: true (5>2)
b < 5: true (3<5)
a == 5: true
true && true = true
true | true = true

🔧 Debug

advanced

What error does this Java code produce due to operator precedence?

Examine this code snippet:

int x = 10;
int y = 20;
boolean check = x < y && x++ > 5 || y-- < 15;

What error or output does this code produce?

Java

int x = 10;
int y = 20;
boolean check = x < y && x++ > 5 || y-- < 15;
System.out.println(check);
System.out.println(x);
System.out.println(y);

A true, x=11, y=20

B true, x=11, y=19

C false, x=10, y=19

D Compilation error

💡 Hint

Remember the order of evaluation and side effects of post-increment and post-decrement.

Operator precedence: && higher than ||.
Expression: (x < y && x++ > 5) || (y-- < 15)
x=10, y=20
x < y: true
x++ > 5: post-increment uses 10 > 5 (true), then x=11
true && true = true
|| short-circuits (left true), so y-- not evaluated, y=20
Output: true, 11, 20

📝 Syntax

advanced

Which option causes a syntax error due to operator misuse in Java?

Which of the following Java code snippets will cause a syntax error?

A int d = 7 % 3 + 1;

B int b = (4 + 5) * 2;

C int c = 10 / 2 - 3;

D int a = 5 + * 3;

💡 Hint

Look for invalid operator combinations.

Option D has 5 + * 3 which is invalid syntax.
Options A, B, and C are valid arithmetic expressions.

🚀 Application

expert

How many items are in the resulting array after this Java expression?

Consider this Java code:

int[] arr = {1, 2, 3, 4, 5};
int[] result = new int[arr.length];
for (int i = 0; i < arr.length; i++) {
    result[i] = arr[i]++ * --arr[i];
}

How many elements in result are greater than 0 after this loop?

Java

int[] arr = {1, 2, 3, 4, 5};
int[] result = new int[arr.length];
for (int i = 0; i < arr.length; i++) {
    result[i] = arr[i]++ * --arr[i];
}
int count = 0;
for (int val : result) {
    if (val > 0) count++;
}
System.out.println(count);

A 4

B 2

C 5

D 3

💡 Hint

Understand how post-increment and pre-decrement affect the value used in multiplication.

For each i, arr[i]++ * --arr[i]:
- arr[i]++: uses original n, then arr[i] = n+1
- --arr[i]: arr[i] = n, uses n
- n * n = n² > 0 for all original values 1-5
Operations cancel out per element, result = [1,4,9,16,25], all >0, count=5