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Array to ArrayList

Certification: Basic Level Accuracy: 70% Submissions: 10 Points: 5

Write a Java program that demonstrates how to convert an Array to an ArrayList and vice versa. Implement methods that handle primitive arrays, object arrays, and perform the conversions efficiently.

Example 1
    

  • Input: Integer[] array = {1, 2, 3, 4, 5}
    • 

  • Output: ArrayList [1, 2, 3, 4, 5] and back to Array [1, 2, 3, 4, 5]
    • 

  • Explanation:

      

    • Convert Integer array to ArrayList
      • 

    • Then convert ArrayList back to array
      • 

    • Elements remain in same order in both conversions
      • 

    

    •
Example 2
    

  • Input: String[] array = {"apple", "banana", "orange"}
    • 

  • Output: ArrayList [apple, banana, orange] and back to Array [apple, banana, orange]
    • 

  • Explanation:

      

    • Convert String array to ArrayList
      • 

    • Then convert back to original array format
      • 

    • Order and content are preserved
      • 

    

    •
Constraints
    

  • 0 ≤ array.length ≤ 10^5
    • 

  • Array can be primitive or object type
    • 

  • Time Complexity: O(n)
    • 

  • Space Complexity: O(n)
    •
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Hint
Solution

Solution Hints

    
  
  • Use Arrays.asList() for quick conversion from array to ArrayList
    • 
  
  • Remember that Arrays.asList() creates a fixed-size list backed by the original array
    • 
  
  • For primitive arrays, you need to perform manual conversion or use wrapper classes
    • 
  
  • ArrayList's toArray() method can be used to convert back to an array
    • 
  
  • Consider using streams for more elegant solutions in Java 8+
    •

Steps to solve by this approach:

 Step 1: For object arrays, use Arrays.asList() and pass it to ArrayList constructor.
 Step 2: For ArrayList to array conversion, use the toArray() method with an array of the proper type.
 Step 3: For primitive arrays like int[], create a special method that manually adds each element to the ArrayList.
 Step 4: When converting back to arrays, pass an empty array of the correct type to toArray().
 Step 5: Handle edge cases like null arrays and empty collections.
 Step 6: Consider using Java streams for more concise conversions in modern Java.
 Step 7: Test with different data types to ensure the generic methods work correctly.

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