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What happens when a duplicate key is put into a HashMap?
...bject, that object becomes eligible for garbage collection. Additionally, Java returns any previous value associated with the given key (or null if none present), so you can determine what was there and maintain a reference if necessary.
More information here: HashMap Doc
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Does Java have something like C#'s ref and out keywords?
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No, Java doesn't have something like C#'s ref and out keywords for passing by reference.
You can only pass by value in Java. Even references are passed by value. See Jon Skeet's page about parameter passing in Java for more deta...
What is the best Java email address validation method? [closed]
What are the good email address validation libraries for Java? Are there any alternatives to commons validator ?
19 Answe...
Why is it not possible to extend annotations in Java?
I don't understand why there is no inheritance in Java annotations, just as Java classes. I think it would be very useful.
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Why am I not getting a java.util.ConcurrentModificationException in this example?
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Here's why:
As it is says in the Javadoc:
The iterators returned by this class's iterator and listIterator
methods are fail-fast: if the list is structurally modified at any
time after the iterator is created, in any way except through the
iterator...
Can enums be subclassed to add new elements?
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No, you can't do this in Java. Aside from anything else, d would then presumably be an instance of A (given the normal idea of "extends"), but users who only knew about A wouldn't know about it - which defeats the point of an enum being a well-known ...
Is there a way to instantiate a class by name in Java?
...ow to instantiate a class when having its name. Is there a way to do it in Java? I will have the package name and class name and I need to be able to create an object having that particular name.
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Android Studio - Ambiguous method call getClass()
...ac). This will navigate to a path such as $ANDROID_HOME/sources/android-20/java/lang/Object.java. Now, within IntelliJ or Android Studio:
Make Object.java writable by choosing File -> Make File Writable. You may be prompted to do this automatically if you try to edit the file.
Remove the unboun...
Truststore and Keystore Definitions
.... You can actually import a private key and a public certificate into the [java home]/jre/lib/security/cacerts default "truststore". The keytool utility does not make a distinction in the two terms, only in store types (i.e. - JKS vs. PKCS12). For that matter, Java does the same thing in the source ...
Retrieving a List from a java.util.stream.Stream in Java 8
I was playing around with Java 8 lambdas to easily filter collections. But I did not find a concise way to retrieve the result as a new list within the same statement. Here is my most concise approach so far:
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