1Z0-811 Arrays and Methods Practice Question
Which of the following correctly describes the effect of the method call 'Arrays.sort(myArray)' on an array of objects that do not implement Comparable?
⚠ Common exam trap
Test-takers frequently assume the code will not compile (Option A) because they think `Comparable` is required at compile time, but the requirement is enforced at runtime via a cast, leading to a `ClassCastException`.
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
✓
A ClassCastException is thrown at runtime.
When `Arrays.sort(myArray)` is called on an array of objects that do not implement the `Comparable` interface, the method attempts to cast elements to `Comparable` to compare them. Since the objects do not implement `Comparable`, a `ClassCastException` is thrown at runtime. The `Arrays.sort(Object[])` method requires that all elements implement `Comparable`; otherwise, it cannot determine a natural ordering.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The code does not compile because Arrays.sort requires a Comparator.
Why it's wrong here
Arrays.sort(Object[]) compiles; exception at runtime.
- ✓
A ClassCastException is thrown at runtime.
Why this is correct
Elements must implement Comparable.
- ✗
The array is sorted using the natural order of the elements.
Why it's wrong here
Natural order requires Comparable implementation.
- ✗
The array is sorted using the order defined by the elements' equals method.
Why it's wrong here
Sorting uses compareTo, not equals.
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