Primitives, Strings and Operators →hardMultiple ChoiceObjective-mapped

1Z0-811 Primitives, Strings and Operators Practice Question

Exhibit

public class StringTest {
    public static void main(String[] args) {
        String s = "Hello";
        s.concat(" World");
        System.out.println(s);
    }
}

Refer to the exhibit. What is the output?

⚠ Common exam trap

Oracle often tests the immutability of `String` by having candidates assume that methods like `concat()` modify the original object, leading them to pick `HelloWorld` instead of recognizing that the result must be assigned to a variable to be retained.

Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

✓

Hello

The code prints 'Hello' because the `String` variable `str` is assigned the value `"Hello"` and then `str.concat("World")` is called. However, `String` objects are immutable in Java, so `concat()` returns a new string without modifying the original `str`. Since the result of `concat()` is not assigned back to `str`, the original `str` remains `"Hello"`, and `System.out.println(str)` outputs `Hello`.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

✗
HelloWorld
Why it's wrong here
No concatenation performed.
✗
Hello World
Why it's wrong here
concat does not modify original.
✗
Compilation error
Why it's wrong here
Code compiles fine.
✓
Hello
Why this is correct
String is immutable, s unchanged.

Go deeper

1Z0-811 Primitives, Strings and Operators Practice Question

Exhibit

Why each option matters

Option-by-option breakdown

Related to this question