Assignment operators in Java - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of compound assignment with multiplication

What is the output of this Java code snippet?

Java

int a = 5;
a *= 3 + 2;
System.out.println(a);

A 10

B 15

C 25

D Syntax error

💡 Hint

Remember that compound assignments evaluate the right side first, then multiply.

The expression a *= 3 + 2 is equivalent to a = a * (3 + 2). So, a = 5 * 5 = 25.

❓ Predict Output

intermediate

Result of bitwise OR assignment

What will be printed after running this Java code?

Java

int x = 6; // binary 0110
x |= 3;    // binary 0011
System.out.println(x);

A 7

B 5

C 3

D 6

💡 Hint

Bitwise OR sets bits where either operand has a 1.

6 in binary is 0110, 3 is 0011. OR operation gives 0111 which is 7 in decimal.

❓ Predict Output

advanced

Output of chained assignment with increment

What is the output of this Java code snippet?

Java

int a = 2;
int b = 3;
int c = a += b++;
System.out.println(a + "," + b + "," + c);

A 5,4,5

B 5,4,2

C 2,4,5

D 5,3,5

💡 Hint

Remember that b++ uses b's value before incrementing.

b++ uses b's current value (3) then increments b to 4. So a += 3 means a = 2 + 3 = 5. c is assigned this new a value (5). b is now 4.

❓ Predict Output

advanced

Effect of right shift assignment operator

What will be printed after executing this Java code?

Java

int num = 32;
num >>= 3;
System.out.println(num);

A 2

B 4

C 16

D 8

💡 Hint

Right shift divides the number by 2 for each shift.

Right shifting 32 by 3 bits divides it by 2^3 = 8, so 32 / 8 = 4.

❓ Predict Output

expert

Value of variable after complex assignment

What is the value of variable result after running this Java code?

Java

int x = 10;
int y = 5;
int result = 0;
result += x > y ? x -= 3 : y += 3;
System.out.println(result);

A 8

B 10

C 5

D 7

💡 Hint

The ternary operator chooses which assignment to perform based on the condition.

Since x (10) > y (5), the true branch executes: x -= 3, so x becomes 7. Then result += 7, so result is 7.

Practice

1. What does the assignment operator += do in Java?

easy

A. Divides the left variable by the right value

B. Subtracts the right value from the left variable

C. Multiplies the left variable by the right value

D. Adds the right value to the left variable and stores the result in the left variable

Solution

1. Step 1: Understand the += operator

   The += operator adds the right-hand side value to the left-hand side variable.

2. Step 2: Store the result back in the left variable

   The sum replaces the original value in the left variable.

3. Final Answer:

   Adds the right value to the left variable and stores the result in the left variable -> Option D

4. Quick Check:

   x += y means x = x + y [OK]

Hint: Think: add then assign back to the same variable [OK]

Common Mistakes:

• Confusing += with subtraction or multiplication
• Thinking it only adds without assignment
• Mixing up the order of operands

2. Which of the following is the correct syntax to multiply a variable num by 5 and assign the result back to num?

easy

A. num = * 5;

B. num *= 5;

C. num = num *;

D. num = 5 *;

Solution

1. Step 1: Identify the correct compound assignment syntax

   The operator *= multiplies and assigns in one step.

2. Step 2: Check the variable and value placement

   The correct form is num *= 5; which means num = num * 5;.

3. Final Answer:

   num *= 5; -> Option B

4. Quick Check:

   Use *= for multiply and assign [OK]

Hint: Look for operator before equals for combined action [OK]

Common Mistakes:

• Placing * after = without variable
• Leaving out the variable on right side
• Using invalid syntax like num = * 5

3. What is the output of this Java code?

int a = 10;
a -= 3;
a += 2;
System.out.println(a);

medium

A. 9

B. 11

C. 5

D. 15

Solution

1. Step 1: Calculate a -= 3;

   Subtract 3 from 10: 10 - 3 = 7, so a becomes 7.

2. Step 2: Calculate a += 2;

   Add 2 to 7: 7 + 2 = 9, so a becomes 9.

3. Step 3: Check the printed value

   The code prints the current value of a, which is 9.

4. Final Answer:

   9 -> Option A

5. Quick Check:

   10 - 3 + 2 = 9 [OK]

Hint: Perform each assignment step in order carefully [OK]

Common Mistakes:

• Adding before subtracting
• Mixing up += and -= effects
• Printing before assignment changes

4. Find the error in this code snippet:

int x = 5;
x + = 3;
System.out.println(x);

medium

A. Variable x is not initialized

B. Missing semicolon after System.out.println(x)

C. The operator + = has a space and is invalid

D. The code will print 8 without errors

Solution

1. Step 1: Check the operator syntax

   The operator += must not have spaces; + = is invalid.

2. Step 2: Confirm other syntax elements

   Variable x is initialized and semicolons are correct.

3. Final Answer:

   The operator + = has a space and is invalid -> Option C

4. Quick Check:

   No spaces allowed in compound assignment operators [OK]

Hint: Compound operators have no spaces, write as one token [OK]

Common Mistakes:

• Adding spaces inside operators
• Assuming code runs despite syntax errors
• Confusing initialization errors with operator errors

5. Given the code below, what is the final value of total?

int total = 20;
int discount = 5;
total -= discount *= 2;
System.out.println(total);

hard

A. 10

B. 30

C. 15

D. 5

Solution

1. Step 1: Evaluate discount *= 2;

   This multiplies discount by 2: 5 * 2 = 10, so discount becomes 10.

2. Step 2: Calculate total -= discount;

   Subtract discount (now 10) from total (20): 20 - 10 = 10.

3. Step 3: Confirm final value

   The final value of total is 10, which is printed.

4. Final Answer:

   10 -> Option A

5. Quick Check:

   discount = 5*2=10; total = 20-10=10 [OK]

Hint: Evaluate right side first in compound assignments [OK]

Common Mistakes:

• Ignoring that discount changes before subtraction
• Subtracting original discount value (5) instead of updated (10)
• Confusing order of operations in assignment