How to Count Unique Dates in a String: A Simple Java Solution

Struggling to count unique dates in a string split by newlines? Discover an effective Java method to easily determine unique dates in each string section.
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This video is based on the question https://stackoverflow.com/q/66829465/ asked by the user 'Shihab365' ( https://stackoverflow.com/u/11212298/ ) and on the answer https://stackoverflow.com/a/66829571/ provided by the user 'Tim Biegeleisen' ( https://stackoverflow.com/u/1863229/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Count Unique Dates in a String: A Simple Java Solution

When dealing with large strings that contain dates, one common challenge is determining the number of unique dates present in various segments of the string. This problem can arise especially if the string is formatted with distinct parts, often separated by newlines ('\n'). Let's explore how to solve this problem effectively with Java.

The Challenge

Suppose you have a string that contains date values, organized into three parts separated by newlines. Your goal is to count the unique dates in each of these segments. A sample output could look like this: 2,2,3 — indicating that the first and second parts each contain two unique dates, while the third part contains three.

However, in your initial implementation, you encountered an issue where the output turned out to be incorrect: 5,5,5,5,1,3,1. This inconsistency hints at a logic error in how the unique dates were being counted.

Understanding the Solution

To count the unique dates accurately, we can employ a Set in Java, which inherently only allows unique items. Below, we'll break down the solution step-by-step, showing how to implement this logic in your code.

Step 1: Set Up Your String

First, you need to create your initial string containing the dates:

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Step 2: Split the String

Next, you split the string into its parts using the newline character:

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Step 3: Count Unique Dates

Now, for each split part, you will count the unique dates by converting it into a Set:

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Explanation:

line.split(",") breaks the date string into an array of individual dates.

The HashSet is initialized with this array, which automatically handles duplicate values.

The size() method of the HashSet gives the count of unique dates.

Step 4: Display the Result

Finally, you can print the results to see your unique date counts:

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Final Implementation

Putting it all together, your revised code will look like this:

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Conclusion

With this straightforward approach using sets, you can effectively count the unique dates in each part of a string. By following the steps outlined in this guide, you should be able to resolve any similar issues with counting unique items efficiently in Java. Happy coding!

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