Fix out-of-bounds access and identity comparison in FibonacciSearch

[SEPURI-SAI-KRISHNA]

The final probe in FibonacciSearch.find has two defects:

if (fibMinus1 == 1 && array[offset + 1] == key) {
    return offset + 1;
}

1. Out-of-bounds read. When the key is greater than every element, the main loop advances offset all the way to n - 1, so array[offset + 1] reads past the end:

new FibonacciSearch().find(new Integer[] {10, 20, 30, 40}, 50);
// java.lang.ArrayIndexOutOfBoundsException: Index 4 out of bounds for length 4

The method is documented to return -1 when the key is absent. Randomised testing over sorted Integer arrays of length 1–12 throws on roughly 6% of inputs.

2. Reference equality instead of value comparison. == compares object identity, not the values. It happens to work for small Integer values because of the Integer cache (−128..127), which is why the existing tests pass, but it fails for anything else:

new FibonacciSearch().find(new Integer[] {10, 20, 300}, 300);   // -1, expected 2
new FibonacciSearch().find(new String[] {"a", "b", "c"}, key);  // -1 for a non-interned "c"

Since T extends Comparable<T>, compareTo is the right comparison here and is consistent with the rest of the method.

Fix

if (fibMinus1 == 1 && offset + 1 < n && array[offset + 1].compareTo(key) == 0) {
    return offset + 1;
}

Tests

• testFibonacciSearchKeyGreaterThanLastElement — a key above the maximum for lengths 1–50 must return -1, not throw.
• testFibonacciSearchFindsEqualButNotIdenticalKey — an Integer outside the cache and a non-interned String.
• testFibonacciSearchFindsEveryElement — every index of every array of length 1–50, with values above the Integer cache.

All three fail on master and pass with the fix.

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[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.43%. Comparing base (55f551b) to head (acf1090).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #7557      +/-   ##
============================================
+ Coverage     80.42%   80.43%   +0.01%     
- Complexity     7459     7462       +3     
============================================
  Files           815      815              
  Lines         24056    24056              
  Branches       4733     4733              
============================================
+ Hits          19347    19350       +3     
  Misses         3945     3945              
+ Partials        764      761       -3     

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[DenizAltunkapan]

@SEPURI-SAI-KRISHNA thank you for your contribution