java-faq

Sometimes when I run my app I get a similar error: Exception in thread "main" java.lang.NullPointerException at com.e ... cing. Translation of the question: "What is a stack trace, and how can I use it to debug my application errors?" @Rob Hruska

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There is often a need to work with Json, in particular its reading and parsing. In Java, you usually know what type of variab ... "type": "home", "number": "999 111-1234" } ] } ] }

In my program, I used the == operator to compare strings. But I came across a bug, and when replacing == with equals, it disappeared. Should the == operator be avoided? When can it be used and when not? What's the difference?

null is it an instance of something? What type does null belong to? What is null? How is it represented in memory? Free translation of the question "What is null in Java?" from the participant @unj2.

What is the best way to write micro-tests/performance tests in Java? What are the main points to pay attention to?

There is a collection and a loop foreach: List<String> someList = new ArrayList<String>(); //add "monkey", "donk ... reach loop above look like? How does the foreach loop work inside? What is the difference between the for and foreach cycles?

What is the difference between the methods Stream.map and Stream.flatMap apart from each other?

What is the difference between TimeUnit.SECONDS.sleep(1); and this.wait(1000)?

Question about using the Function.identity() method. Let's say there is the following code: Arrays.asList("a", "b", "c") ... he new person does not know what identity is doing). But is there a "real" reason why one of the methods should be preferred?

Which of the following is the best practice in Java 8? Java 8: list.forEach(e -> e.operation); Java 7: for (E e : lis ... bdas, but are there any real benefits from using Iterator.foreach? Will the performance and readability of the code improve?

I don't really understand the difference between findFirst() and findAny() in the Java Stream API. I thought that findFirst ... and Stream.of(...).findAny() Then they both return the first element of the stream. Why? Are they both doing the same task?