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System.currentTimeMillis vs System.nanoTime
...you a nanosecond-precise time, relative to some arbitrary point.
From the Java Documentation:
public static long nanoTime()
Returns the current value of the most precise available system timer, in nanoseconds.
This method can only be used to
measure elapsed time and is not
related ...
Is it good practice to make the constructor throw an exception? [duplicate]
... a checked exception for this2.
However explicitly declaring or throwing java.lang.Exception is almost always bad practice.
You should pick an exception class that matches the exceptional condition that has occurred. If you throw Exception it is difficult for the caller to separate this exceptio...
How to properly override clone method?
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Do you absolutely have to use clone? Most people agree that Java's clone is broken.
Josh Bloch on Design - Copy Constructor versus Cloning
If you've read the item about cloning in my book, especially if you read between the lines, you will know that I think clone is deeply broken...
What is the difference between iterator and iterable and how to use them?
I am new in Java and I'm really confused with iterator and iterable. Can anyone explain to me and give some examples?
13 An...
Java: how do I get a class literal from a generic type?
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You can't due to type erasure.
Java generics are little more than syntactic sugar for Object casts. To demonstrate:
List<Integer> list1 = new ArrayList<Integer>();
List<String> list2 = (List<String>)list1;
list2.add("foo"); // perf...
compareTo() vs. equals()
When testing for equality of String 's in Java I have always used equals() because to me this seems to be the most natural method for it. After all, its name already says what it is intended to do. However, a colleague of mine recently told me had been taught to use compareTo() == 0 instead of ...
Java 8 method references: provide a Supplier capable of supplying a parameterized result
...ise you will get an error message like MyException cannot be converted to java.lang.RuntimeException
Update:- This was an issue with an older version of JDK. I don't see this issue with the latest versions.
share
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Is List a subclass of List? Why are Java generics not implicitly polymorphic?
I'm a bit confused about how Java generics handle inheritance / polymorphism.
17 Answers
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Convert JsonNode into POJO
...he official documentation for that call: http://jackson.codehaus.org/1.7.9/javadoc/org/codehaus/jackson/map/ObjectMapper.html#readValue(java.lang.String, java.lang.Class)
You can also define a custom deserializer when you instantiate the ObjectMapper:
http://wiki.fasterxml.com/JacksonHowToCustomDes...
Why does InetAddress.isReachable return false, when I can ping the IP address?
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Here are other, similar questions :
Detect internet Connection using Java
How do I test the availability of the internet in Java?
And even a reported bug on this same matter :
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4921816
Part 1 : A reproducible example of the problem
Note t...