Core Concept Questions

1. What is an array in Java?
   An array is a container object that holds a fixed number of elements of the same type. Its size is determined at creation and cannot be changed later ().

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2. How do you declare, instantiate, and initialize an array?
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int[] numbers = new int; // declaration and instantiation [^2^]
int[] nums = {1, 2, 3, 4, 5}; // declaration and initialization

3. What are the default values of array elements?
   Numeric arrays default to 0, boolean arrays to false, and object arrays to null ().

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4. What are the advantages and disadvantages of arrays?
   Advantages: fast access via index, memory efficiency, easy iteration.
   Disadvantages: fixed size, costly insertion/deletion in the middle ().

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Multidimensional and Special Arrays

5. What is a multidimensional array?
   Arrays containing arrays, e.g., int[][] matrix = new int;.

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6. What is a jagged array?
   A multidimensional array where subarrays have different lengths ().

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7. Difference between static and dynamic arrays?
   Static arrays have fixed size; dynamic arrays (like ArrayList) can grow or shrink.
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Common Coding Questions

8. Find the largest and smallest elements in an array.
9. Reverse an array in-place.
10. Find the second largest element.
11. Rotate an array by k positions.
12. Find missing numbers in a sequence.
13. Remove duplicates from an array.
14. Merge two sorted arrays without extra space.
15. Find the maximum sum subarray (Kadane’s Algorithm).
16. Find duplicates without using extra space.
17. Find the intersection of two arrays efficiently.
18. Explain shallow copy vs deep copy in arrays. ()

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Array Manipulation and Utilities

19. How to copy arrays in Java?
    Use System.arraycopy() or loop through elements ().

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20. Sorting arrays
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• Primitive types: Arrays.sort(array) uses Dual-Pivot Quicksort.
• Objects: Arrays.sort(array) uses Mergesort for natural ordering ().

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21. Searching elements
    Linear search for unsorted arrays, binary search for sorted arrays using Arrays.binarySearch().

Advanced Topics

22. Sparse arrays and their benefits.
23. Difference between subarray and subsequence.
24. Row-major vs column-major order in arrays. ()

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Preparation Tips

• Practice coding problems from easy to hard levels ().

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• Understand time and space complexity for array operations.
• Be familiar with common Java array methods in java.util.Arrays.
• Review edge cases like empty arrays, single-element arrays, and null arrays.
  These questions cover both conceptual understanding and practical coding skills, making them highly relevant for Java programming interviews across all experience levels ().

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