Java Assertion Error
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Questions Jobs Documentation Tags Users Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow is a community of java assertionerror example 4.7 million programmers, just like you, helping each other. Join them; it only takes a minute: Sign up What is an AssertionError? In which case should I throw it from my own code? up vote 25
Java Lang Assertionerror In Junit Test
down vote favorite 5 In Item 2 of the "Effective Java, 2nd edition" book, there is this snippet of code, in which the author wants to forbid the empty initialization of an object. class Example { private Example() { throw new AssertionError(); } } The type of exception thrown, is what confuses me here. I don't understand if the AssertionError is thrown just because of an absence of more suited errors or because catch assertionerror it should be this way. As I understand, this error is thrown by the framework when an assert statement fails. Also, in the javadoc it's just written [An AssertionError is] Thrown to indicate that an assertion has failed. But I don't see any assertion (true-false statement) being violated here. Of course the "You shall not instantiate an item of this class" statement has been violated, but if this is the logic behind that, then we should all throw AssertionErrors everywhere, and that is obviously not what happens. FWIW, I'd have just thrown a new IllegalStateException("Must not instantiate an element of this class") Is there something wrong with that? In which case should I throw an AssertionError in my own code? Sorry if it's just a subtle doubt but I use this pattern a lot in my code and I want to make sure I'm doing the right thing. java exception effective-java share|improve this question edited Jul 21 '14 at 11:03 asked Jul 21 '14 at 10:43 doplumi 89221331 1 "Assertions" doesn't just mean "assert statements". –immibis Jul 21 '14 at 10:45 add a comment| 3 Answers 3 active oldest votes up vote 19 down vote accepted Of course the "You shall not instantiate an item of this class" statement has been violated, but i
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How To Handle Assertion Error In Java
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the Stack Overflow Community Stack Overflow is a community of 4.7 million programmers, just like you, helping each other. Join them; it only takes assertionerror django a minute: Sign up Java assertion error does not throw error up vote 6 down vote favorite Why doesn't my assert statement yield any result? I think the first assert statement should fail, but I don't see anything being displayed on http://stackoverflow.com/questions/24863185/what-is-an-assertionerror-in-which-case-should-i-throw-it-from-my-own-code Eclipse. I'm using Eclipse to run this program. package java.first; public class test { public static void main(String[] args) throws Exception { String s = "test1"; assert (s == "test"); s = "test"; assert (s == "test"); } } java eclipse assert share|improve this question edited Jul 29 '13 at 17:32 arshajii 80.1k15135206 asked Jul 29 '13 at 17:22 user1050619 3,5892065128 add a comment| 5 Answers 5 active oldest votes up vote 15 down vote You need to set the -ea (Enable http://stackoverflow.com/questions/17930266/java-assertion-error-does-not-throw-error Assertions) in your JVM options. Unrelated, but you almost always want string1.equals(string2) rather than ==. share|improve this answer answered Jul 29 '13 at 17:24 Dave Newton 119k13162195 to elaborate on that, you can understand the == operator like it answers the following question: the reference to this object points to the same reference of this other object? are this 2 guys allocated in the same chunk of memory, which is only true if it exists 1 and only 1 instance of such object in the whole context of you application (singleton). In other words an instance of an object is only == to itself. Since you are comparing it to another instance which holds the same value you need to use equalsmethod as stated above. –VallaDanger Apr 28 at 18:12 when you say (s == "test") you are actually creating a new instance of String with the value test, so asking if that new instance is == to s is absolutely not trueunless you use the String.intern() method which will ensure that all strings having same values share same memory. There is actually much more to know about objects equality, reason why I would recommend giving effective java (2nd edition, Chapter 3, item 8) a chance. –VallaDanger Apr 28 at 18:31 add a comment| up vote 4 down vote You need to turn assertion checking on at runtime. The Oracle documentation for Java states: To enable assertions at vario
here for a quick overview of the site Help Center Detailed answers to any questions you might have Meta Discuss the workings and http://stackoverflow.com/questions/29671796/will-an-assertion-error-be-caught-by-in-a-catch-block-for-java-exception policies of this site About Us Learn more about Stack Overflow the company Business Learn more about hiring developers or posting ads with us Stack Overflow Questions Jobs Documentation Tags Users Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 4.7 million programmers, just like you, helping each other. Join them; it only assertion error takes a minute: Sign up Will an assertion error be caught by in a catch block for java exception? up vote 7 down vote favorite Code:- try { Assert.assertEquals("1", "2"); } catch (Exception e) { System.out.println("I am in error block"); } If the assert statements fails, I would like to capture the error in the catch block. I am trying with java assertion error the above code and its not happening. Will the assertion error be caught by in a catch block for java exception? java junit try-catch assert share|improve this question edited Apr 16 '15 at 10:32 J Richard Snape 14.6k42352 asked Apr 16 '15 at 10:19 karan 856724 Why would you want to do that anyways? This seems like a gross misuse of Assert which is meant for Unit Testing –Dragondraikk Apr 16 '15 at 10:25 add a comment| 3 Answers 3 active oldest votes up vote 16 down vote accepted You have almost answered your own question. Your catch block will not catch the AssertionError that the Assert throws if it fails, because it is an Error (or, more specifically, it extends java.lang.Error). See the docs for more information on this. Your catch block only catches Throwable objects that extend java.lang.Exception If you really want to catch it - you need to use catch (AssertionError e) { ... However, as others have mentioned, this is a very unusual way to use assertions - they should usually pass and if the