Mizuho Fixed Income Team Lead position Interview coding round questions

Sting s = “test” what will be output of s==”test”

In Java, the == operator compares object references, not the actual content of the strings. So when you use s == "test", you’re checking if the reference of the string s is the same as the reference of the string literal "test".

In this case:

String s = "test";

The string literal "test" is interned, meaning that it is stored in a common pool, and any string literal with the same value will refer to the same object in this pool. Therefore, s and "test" both refer to the same interned string object. As a result:

s == "test"

will evaluate to true.

However, for string content comparison, you should use the .equals() method:

s.equals("test")

This method compares the actual content of the strings, and in this case, it would also return true since the content of s and "test" is the same.

Implement this method: public static Collection<String> removeDuplicatesAndSort(Collection<String> names) { }

To implement a method that removes duplicates from a Collection<String> and sorts the remaining elements, you can use a Set to handle duplicate removal and then sort the Set using a List. Here’s a sample implementation:

import java.util.Collection;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import java.util.ArrayList;
import java.util.Collections;

public class StringUtils {

    public static Collection<String> removeDuplicatesAndSort(Collection<String> names) {
        // Create a Set to remove duplicates
        Set<String> uniqueNames = new HashSet<>(names);
        
        // Convert the Set to a List for sorting
        List<String> sortedList = new ArrayList<>(uniqueNames);
        
        // Sort the List
        Collections.sort(sortedList);
        
        return sortedList;
    }

    public static void main(String[] args) {
        // Example usage
        Collection<String> names = List.of("banana", "apple", "orange", "apple", "banana");
        Collection<String> result = removeDuplicatesAndSort(names);
        System.out.println(result); // Output: [apple, banana, orange]
    }
}

Explanation:

1. Remove Duplicates: Convert the Collection<String> to a Set (specifically a HashSet), which inherently removes any duplicate entries.
2. Sort Elements: Convert the Set back to a List (specifically an ArrayList) so that you can sort it. Use Collections.sort() to sort the List.
3. Return Sorted List: Return the sorted List, which contains the unique and sorted strings.

In this example, the main method demonstrates how to use the removeDuplicatesAndSort method with a sample Collection. Adjust the implementation as needed for your specific use case.

Can you write some better way for improvement of above code?

Certainly! The previous implementation is straightforward and effective, but it can be streamlined or improved in a few ways:

1. Using Streams (Java 8+): If you’re using Java 8 or later, you can take advantage of the Streams API to make the code more concise and expressive.
2. Returning an Immutable Collection: Instead of returning a mutable List, you might want to return an immutable collection to avoid accidental modification.

Here’s an improved version of the method using Java Streams and returning an immutable List:

import java.util.Collection;
import java.util.List;
import java.util.stream.Collectors;

public class StringUtils {

    public static List<String> removeDuplicatesAndSort(Collection<String> names) {
        return names.stream()                     // Convert Collection to Stream
                    .distinct()                  // Remove duplicates
                    .sorted()                    // Sort the elements
                    .collect(Collectors.toUnmodifiableList()); // Collect to an immutable List
    }

    public static void main(String[] args) {
        // Example usage
        Collection<String> names = List.of("banana", "apple", "orange", "apple", "banana");
        List<String> result = removeDuplicatesAndSort(names);
        System.out.println(result); // Output: [apple, banana, orange]
    }
}

Improvements:

1. Streams API:
   • .distinct() removes duplicates.
   • .sorted() sorts the elements.
   • .collect(Collectors.toUnmodifiableList()) collects the result into an immutable list.
2. Immutability: The use of Collectors.toUnmodifiableList() ensures that the returned list cannot be modified, which is often a good practice to prevent unintended changes.
3. Conciseness: The Stream-based approach is more compact and expressive, leveraging the power of functional programming.

This version is more elegant and takes advantage of modern Java features to improve readability and maintainability.