1Z0-811 Arrays and Methods Practice Question
A banking application stores daily transaction amounts in an array. Which declaration correctly creates an array of 31 double values?
⚠ Common exam trap
Oracle often tests the distinction between array size and index range, tricking candidates into choosing an array of size 30 (index 0-29) when 31 elements are needed, or confusing the data type (int vs double) for monetary values.
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
✓
double[] transactions = new double[31];
It uses the proper syntax to declare an array of double values and initializes it with a size of 31, which allocates memory for 31 double elements, each defaulting to 0.0. In Java, the array size must be specified when using the 'new' keyword, and the index range is 0 to 30, accommodating exactly 31 daily transaction amounts.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
double[] transactions = new double[31];
Why this is correct
Correct syntax: declares array and allocates 31 elements.
- ✗
double transactions[] = new double[30];
Why it's wrong here
Only allocates 30 elements, not 31.
- ✗
int[] transactions = new int[31];
Why it's wrong here
Data type should be double, not int.
- ✗
double[] transactions = new double[];
Why it's wrong here
Missing size; compilation error.
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