'Why does ConcurrentHashMap.computeIfAbsent() increment the counter for an already present key?

Running this example code (from Cay Horstmann)

ConcurrentHashMap<String,LongAdder> counts = new ConcurrentHashMap<>();
for (String key : "Row, row, row a boat".split("\\PL+"))
    counts.computeIfAbsent(key, k -> new LongAdder()).increment();
System.out.println(counts);

The output is

{a=1, Row=1, row=2, boat=1}

I am surprised to see row=2 because I expected computeIfAbsent() would increment only when it found the first "row" and not the second one.

javapythonseleniumweb-scrapingbeautifulsoupebay-api


Solution 1:[1]

Using vanilla Selenium generally leads to CAPTCHA / blocks due to the browser not hiding its identity as a browser automation.

I suggest trying out undetected_chromedriver - a slightly modified version of Selenium that circumvents most automated bot-detection protocols.

From the project's description:

[undetected_chromedriver is an...] optimized Selenium Chromedriver patch which does not trigger anti-bot services like Distill Network / Imperva / DataDome / Botprotect.io

I've used it quite a bit and it almost always works exactly as intended.

Here's some code to get you started:

import undetected_chromedriver.v2 as uc

# ADD CHROME OPTION -> DISABLE POPUP BLOCKING
options = uc.ChromeOptions()
options.add_argument("--disable-popup-blocking")
driver = uc.Chrome(options=options)

driver.get('https://amazon.com/')

You can visit the project's GitHub for more information. Keep in mind that you'll need to use slightly different syntax vis-a-vis regular Selenium when using certain functions.

Also, you don't need to download chromedriver.exe, as the module automatically downloads the latest version.

Sources

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Source: Stack Overflow

Solution Source
Solution 1 Robby Frank

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