The correct answer is that StringBuilder can be used to create mutable strings, as String objects themselves are immutable in Java. This is true because once a String object is created, its value cannot be changed; any operation that appears to modify a String actually creates a new object in memory. The intern() method reinforces this by returning a canonical representation from the string pool, ensuring identical string literals share the same reference for memory efficiency—a direct consequence of immutability. On the Oracle Java Foundations 1Z0-811 exam, this topic tests your understanding of how immutability affects performance and memory management, often appearing in questions that contrast String with StringBuilder or StringBuffer. A common trap is assuming that methods like toUpperCase() modify the original String, when in fact they return a new object. Remember the mnemonic: “Strings stay, builders change”—String objects are fixed, while StringBuilder lets you modify content without creating new objects.
1Z0-811 Primitives, Strings and Operators Practice Question
This 1Z0-811 practice question tests your understanding of primitives, strings and operators. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Which three statements about String immutability are true? (Choose three)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The intern() method returns a String from the pool
Option C is correct because the `intern()` method returns a canonical representation of the string from the string pool, ensuring that strings with the same content share the same memory reference, which is a key aspect of immutability and memory optimization in Java.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
String objects can be modified after creation
Why it's wrong here
False; Strings are immutable.
✗
String objects can be changed by calling methods
Why it's wrong here
False; methods return new Strings, not modify original.
✓
The intern() method returns a String from the pool
Why this is correct
True; intern() returns canonical representation.
Related concept
Read the scenario before looking for a memorised answer.
✓
String concatenation creates a new String
Why this is correct
True; concatenation returns new String.
Related concept
Read the scenario before looking for a memorised answer.
✓
StringBuilder can be used to create mutable strings
Why this is correct
True; StringBuilder is mutable.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Oracle often tests the misconception that calling a method on a String changes the original object, when in fact all such methods return a new String, leaving the original unchanged.
Detailed technical explanation
How to think about this question
Under the hood, String immutability is enforced by the `final` keyword on the class and its internal `char[]` (or `byte[]` in modern Java) array, which is not exposed for modification. This design allows safe caching of hash codes, efficient string pooling, and thread safety without synchronization. A subtle behavior is that string concatenation using the `+` operator is compiled to `StringBuilder.append()` calls, but the result is still a new immutable String.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Primitives, Strings and Operators — This question tests Primitives, Strings and Operators — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The intern() method returns a String from the pool — Option C is correct because the `intern()` method returns a canonical representation of the string from the string pool, ensuring that strings with the same content share the same memory reference, which is a key aspect of immutability and memory optimization in Java.
What should I do if I get this 1Z0-811 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Which TWO statements are true about the String class in Java? (Choose 2)
medium
A.String is mutable if created with new.
B.String implements the Cloneable interface.
✓ C.Strings are immutable.
D.String objects can be modified using methods like toUpperCase().
✓ E.The intern() method can add a string to the string pool.
Why C: Option A and B are correct. A: Strings are immutable. B: String pool intern method. C is wrong because Strings are not mutable. D is wrong because String does not implement Cloneable. E is wrong because StringBuilder is mutable.
Variation 2. Which of the following statements about the String class is true?
hard
A.Strings can be modified using the '+' operator
B.String objects can be created only with the 'new' keyword
✓ C.Strings are immutable
D.String is a primitive type
Why C: Option C is correct because String objects in Java are immutable, meaning once a String object is created, its value cannot be changed. Any operation that appears to modify a String, such as concatenation, actually creates a new String object. This immutability is a fundamental design choice that enables String pooling, thread safety, and efficient caching of hash codes.
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Question Discussion
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