Unit 1 Day 8: String Concatenation Practice
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Unit 1, Section 1.8
Day 8 Practice • January 14, 2026
🎯 Focus: String Concatenation
Practice Question
Consider the following code segment:
int x = 5;
int y = 3;
System.out.println("Sum: " + x + y);What is printed as a result of executing this code segment?
What This Tests: This question tests understanding of String concatenation and operator precedence. When a String is involved with the + operator, Java performs concatenation rather than addition—but order matters!
Key Concept: String Concatenation Order
Java evaluates expressions left to right. When a String appears first, subsequent + operations become concatenation:
"Sum: " + 5 + 3 // → "Sum: 5" + 3 → "Sum: 53"
5 + 3 + " is sum" // → 8 + " is sum" → "8 is sum"
"Sum: " + (5 + 3) // → "Sum: " + 8 → "Sum: 8"Step-by-Step Trace
| Step | Expression | Result |
|---|---|---|
| 1 | "Sum: " + x | "Sum: 5" (String) |
| 2 | "Sum: 5" + y | "Sum: 53" (String) |
Because the String comes first, x is converted to "5" and concatenated, giving "Sum: 5". Then y is converted to "3" and concatenated, giving "Sum: 53".
Common Mistakes
Mistake: Answer A (Sum: 8)
This would require parentheses: "Sum: " + (x + y). Without parentheses, the numbers are concatenated as strings, not added.
How to Force Addition
💡 Use Parentheses!
To add numbers before concatenating with a String, wrap them in parentheses:
System.out.println("Sum: " + (x + y)); // "Sum: 8"Related Topics
- Section 1.3: Operator Precedence
- Section 1.4: String Literals
- Section 1.9: String Methods
Difficulty: Medium • Time: 1-2 minutes • AP Skill: 2.B - Determine output
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