What is a tricky question? Well, tricky Java interview questions are those questions which direct maintain some surprise chemical component on it. If yous endeavour to reply a tricky enquiry amongst mutual sense, yous volition most probable neglect because they require some specific knowledge. Most of the tricky Java questions comes from confusing concepts similar component subdivision overloading as well as overriding, Multi-threading which is truly tricky to master, grapheme encoding, checked vs unchecked exceptions as well as subtle Java programming details similar Integer overflow. Most of import thing to reply a tricky Java enquiry is mental attitude as well as analytical thinking, which helps fifty-fifty if yous don't know the answer. Anyway inward this Java article nosotros volition run across 10 Java questions which are existent tricky as well as requires to a greater extent than than average cognition of Java programming linguistic communication to reply them correctly. As per my experience, in that location is e'er ane or 2 tricky or tough Java interview question on whatever meat Java or J2EE interviews, therefore it's proficient to fix tricky questions from Java inward advance.
If I direct maintain an interview, I purposefully position this variety of enquiry to approximate the depth of candidate's agreement inward Java. Another wages of bespeak such enquiry is the surprising element, which is a key cistron to position the candidate on some pressure level during interviews.
If I direct maintain an interview, I purposefully position this variety of enquiry to approximate the depth of candidate's agreement inward Java. Another wages of bespeak such enquiry is the surprising element, which is a key cistron to position the candidate on some pressure level during interviews.
Since these questions are less common, in that location is proficient adventure that many Java developer doesn't know virtually it. You won't detect these questions fifty-fifty on pop Java interview books similar Java Programming Interview exposed, which is all the same an splendid guide for Java interviews.
Btw, if yous don't detect these enquiry tricky enough, therefore yous should depository fiscal establishment check Joshua Bloch's some other classic book, Java Puzzlers for super tricky questions. I am sure yous volition detect them challenging enough.
What volition give off if yous position render declaration or System.exit () on endeavour or grab block? Will finally block execute?
This is a really pop tricky Java enquiry as well as it's tricky because many programmers think that no thing what, but the finally block volition e'er execute. This enquiry challenge that concept past times putting a render declaration inward the endeavour or grab block or calling System.exit() from endeavour or grab block. Answer of this tricky enquiry inward Java is that finally block volition execute fifty-fifty if yous position a render declaration inward the endeavour block or grab block but finally block won't run if yous telephone band System.exit() from endeavour or grab block.
Question: Can yous override a mortal or static method inward Java?
Another pop Java tricky question, As I said method overriding is a proficient theme to inquire play tricks questions inward Java. Anyway, you tin non override a mortal or static method inward Java, if yous create a similar method amongst same render type as well as same method arguments inward fry course of report therefore it volition enshroud the superclass method, this is known every bit method hiding.
What is the deviation betwixt StringBuffer as well as StringBuilder inward Java?
Classic Java questions which some people think tricky as well as some reckon really easy. StringBuilder inward Java was introduced inward JDK 1.5 as well as the entirely deviation betwixt both of them is that StringBuffer methods e.g. length(), capacity() or append() are synchronized acre corresponding methods inward StringBuilder are non synchronized.
Because of this primal difference, concatenation of String using StringBuilder is faster than StringBuffer. Actually, it's considered the bad practise to occupation StringBuffer anymore, because, inward almost 99% scenario, yous perform string concatenation on the same thread. See StringBuilder vs StringBuffer for to a greater extent than differences.
Can yous access a non-static variable inward the static context?
Another tricky Java enquiry from Java fundamentals. No, yous tin non access a non-static variable from the static context inward Java. If yous try, it volition give compile fourth dimension error. This is truly a mutual job beginner inward Java human face upwards when they endeavour to access instance variable within the master copy method. Because master copy is static inward Java, as well as instance variables are non-static, yous tin non access instance variable within main. See, why yous tin non access a non-static variable from static method to larn to a greater extent than virtually this tricky Java questions.
How many String objects are created past times the next code?
Now, it's practise time, hither are some questions for yous guys to answer, these are contributed past times readers of this blog, big thank yous to them.
Btw, if yous don't detect these enquiry tricky enough, therefore yous should depository fiscal establishment check Joshua Bloch's some other classic book, Java Puzzlers for super tricky questions. I am sure yous volition detect them challenging enough.
10 Tricky Java interview enquiry - Answered
Here is my listing of 10 tricky Java interview questions, Though I direct maintain prepared as well as shared lot of hard meat Java interview enquiry as well as answers, But I direct maintain chosen them every bit Top 10 tricky questions because yous tin non guess answers of this tricky Java questions easily, yous demand some subtle details of Java programming linguistic communication to reply these questions. Question: What does the next Java plan print?
public class Test { public static void main(String[] args) { System.out.println(Math.min(Double.MIN_VALUE, 0.0d)); } }Answer: This enquiry is tricky because dissimilar the Integer, where MIN_VALUE is negative, both the MAX_VALUE as well as MIN_VALUE of the Double course of report are positive numbers. The Double.MIN_VALUE is 2^(-1074), a double constant whose magnitude is the to the lowest degree amid all double values. So dissimilar the obvious answer, this plan volition impress 0.0 because Double.MIN_VALUE is greater than 0. I direct maintain asked this enquiry to Java developer having sense upwards to 3 to v years as well as surprisingly almost 70% candidate got it wrong.
What volition give off if yous position render declaration or System.exit () on endeavour or grab block? Will finally block execute?
This is a really pop tricky Java enquiry as well as it's tricky because many programmers think that no thing what, but the finally block volition e'er execute. This enquiry challenge that concept past times putting a render declaration inward the endeavour or grab block or calling System.exit() from endeavour or grab block. Answer of this tricky enquiry inward Java is that finally block volition execute fifty-fifty if yous position a render declaration inward the endeavour block or grab block but finally block won't run if yous telephone band System.exit() from endeavour or grab block.
Another pop Java tricky question, As I said method overriding is a proficient theme to inquire play tricks questions inward Java. Anyway, you tin non override a mortal or static method inward Java, if yous create a similar method amongst same render type as well as same method arguments inward fry course of report therefore it volition enshroud the superclass method, this is known every bit method hiding.
Similarly, yous cannot override a mortal method inward sub course of report because it's non accessible there, what yous do is create some other mortal method amongst the same advert inward the fry class. See Can yous override a mortal method inward Java or to a greater extent than details.
Question: What do the facial expression 1.0 / 0.0 volition return? volition it throw Exception? whatever compile fourth dimension error?
Answer: This is some other tricky enquiry from Double class. Though Java developer knows virtually the double primitive type as well as Double class, acre doing floating indicate arithmetics they don't pay plenty attending to Double.INFINITY, NaN, as well as -0.0 as well as other rules that principle the arithmetics calculations involving them. The elementary reply to this enquiry is that it volition non throw ArithmeticExcpetion as well as render Double.INFINITY.
Also, Federal Reserve annotation that the comparing x == Double.NaN e'er evaluates to false, fifty-fifty if x itself is a NaN. To attempt if x is a NaN, ane should occupation the method telephone band Double.isNaN(x) to depository fiscal establishment check if given number is NaN or not. If yous know SQL, this is really around NULL there.
Btw, If yous are running out of fourth dimension for your interview preparation, yous tin likewise depository fiscal establishment check out Java Programming Interviews exposed for to a greater extent than of such pop questions,
Does Java back upwards multiple inheritances?
This is the trickiest enquiry inward Java if C++ tin back upwards instantly multiple inheritances than why non Java is the declaration Interviewer often give. Answer of this enquiry is much to a greater extent than subtle therefore it looks like, because Java does back upwards multiple inheritances of Type past times allowing an interface to extend other interfaces, what Java doesn't back upwards is multiple inheritances of implementation. This distinction likewise gets blur because of default method of Java 8, which at nowadays provides Java, multiple inheritances of demeanor every bit well. See why multiple inheritances are non supported inward Java to reply this tricky Java question.
What volition give off if nosotros position a key object inward a HashMap which is already there?
This tricky Java enquiry is component subdivision of some other oft asked question, How HashMap industrial plant inward Java. HashMap is likewise a pop theme to create confusing as well as tricky enquiry inward Java. Answer of this enquiry is if yous position the same key ane time again therefore it volition supersede the former mapping because HashMap doesn't allow duplicate keys. The Same key volition lawsuit inward the same hashcode as well as volition halt upwards at the same seat inward the bucket.
Question: What do the facial expression 1.0 / 0.0 volition return? volition it throw Exception? whatever compile fourth dimension error?
Answer: This is some other tricky enquiry from Double class. Though Java developer knows virtually the double primitive type as well as Double class, acre doing floating indicate arithmetics they don't pay plenty attending to Double.INFINITY, NaN, as well as -0.0 as well as other rules that principle the arithmetics calculations involving them. The elementary reply to this enquiry is that it volition non throw ArithmeticExcpetion as well as render Double.INFINITY.
Also, Federal Reserve annotation that the comparing x == Double.NaN e'er evaluates to false, fifty-fifty if x itself is a NaN. To attempt if x is a NaN, ane should occupation the method telephone band Double.isNaN(x) to depository fiscal establishment check if given number is NaN or not. If yous know SQL, this is really around NULL there.
Btw, If yous are running out of fourth dimension for your interview preparation, yous tin likewise depository fiscal establishment check out Java Programming Interviews exposed for to a greater extent than of such pop questions,
This is the trickiest enquiry inward Java if C++ tin back upwards instantly multiple inheritances than why non Java is the declaration Interviewer often give. Answer of this enquiry is much to a greater extent than subtle therefore it looks like, because Java does back upwards multiple inheritances of Type past times allowing an interface to extend other interfaces, what Java doesn't back upwards is multiple inheritances of implementation. This distinction likewise gets blur because of default method of Java 8, which at nowadays provides Java, multiple inheritances of demeanor every bit well. See why multiple inheritances are non supported inward Java to reply this tricky Java question.
This tricky Java enquiry is component subdivision of some other oft asked question, How HashMap industrial plant inward Java. HashMap is likewise a pop theme to create confusing as well as tricky enquiry inward Java. Answer of this enquiry is if yous position the same key ane time again therefore it volition supersede the former mapping because HashMap doesn't allow duplicate keys. The Same key volition lawsuit inward the same hashcode as well as volition halt upwards at the same seat inward the bucket.
Each bucket contains a linked listing of Map.Entry object, which contains both Key as well as Value. Now Java volition direct maintain the Key object from each entry as well as compare amongst this novel key using equals() method, if that render truthful therefore value object inward that entry volition live replaced past times novel value. See How HashMap industrial plant inward Java for to a greater extent than tricky Java questions from HashMap.
Question: What does the next Java plan print?
Answer: The trickiness of this enquiry lies on grapheme encoding as well as how String to byte array conversion works. In this program, nosotros are get-go creating a String from a grapheme array, which only has ane grapheme '\u0097', afterward that nosotros are getting the byte array from that String as well as printing that byte. Since \u0097 is within the 8-bit attain of byte primitive type, it is reasonable to guess that the str.getBytes() telephone band volition render a byte array that contains ane chemical component amongst a value of -105 ((byte) 0x97).
However, that's non what the plan prints as well as that's why this enquiry is tricky. As a thing of fact, the output of the plan is operating arrangement as well as locale dependent. On a Windows XP amongst the the U.S. locale, the higher upwards plan prints [63], if yous run this plan on Linux or Solaris, yous volition acquire different values.
To reply this enquiry correctly, yous demand to know virtually how Unicode characters are represented inward Java char values as well as inward Java strings, as well as what role grapheme encoding plays inward String.getBytes().
In elementary word, to convert a string to a byte array, Java iterate through all the characters that the string represents as well as plough each ane into a number of bytes as well as finally position the bytes together. The dominion that maps each Unicode grapheme into a byte array is called a grapheme encoding. So It's possible that if same grapheme encoding is non used during both encoding as well as decoding therefore retrieved value may non live correct. When nosotros call str.getBytes() without specifying a grapheme encoding scheme, the JVM uses the default grapheme encoding of the platform to do the job.
The default encoding system is operating arrangement as well as locale dependent. On Linux, it is UTF-8 as well as on Windows amongst a the U.S. locale, the default encoding is Cp1252. This explains the output nosotros acquire from running this plan on Windows machines amongst a the U.S. locale. No thing which grapheme encoding system is used, Java volition e'er interpret Unicode characters non recognized past times the encoding to 63, which represents the grapheme U+003F (the enquiry mark, ?) inward all encodings.
If a method throws NullPointerException inward the superclass, tin nosotros override it amongst a method which throws RuntimeException?
One to a greater extent than tricky Java questions from the overloading as well as overriding concept. The reply is yous tin really good throw superclass of RuntimeException inward overridden method, but yous tin non do same if its checked Exception. See Rules of method overriding inward Java for to a greater extent than details.
How do yous ensure that due north thread tin access due north resources without deadlock?
If yous are non good versed inward writing multi-threading code therefore this is a existent tricky enquiry for you. This Java enquiry tin live tricky fifty-fifty for the experienced as well as senior programmer, who are non truly exposed to deadlock as well as race conditions. The key indicate hither is ordering, if yous acquire resources inward a exceptional lodge as well as liberate resources inward the contrary lodge yous tin forestall deadlock. See how to avoid deadlock inward Java for a sample code example.
Question: Consider the next Java code snippet, which is initializing 2 variables as well as both are non volatile, and 2 threads T1 as well as T2 are modifying these values every bit following, both are non synchronized
Answer: It's impossible for a listing of tricky Java questions to non incorporate anything from multi-threading. This is the simplest ane I tin get. Answer of this enquiry is Yes, It's possible that thread T2 may impress x=0.Why? because without whatever didactics to compiler e.g. synchronized or volatile, bExit=true might come upwards earlier x=1 inward compiler reordering. Also, x=1 powerfulness non transcend away visible inward Thread 2, therefore Thread 2 volition charge x=0. Now, how do yous ready it?
When I asked this enquiry to a pair of programmers they reply differently, ane suggests to brand both threads synchronized on a mutual mutex, some other ane said brand both variable volatile. Both are correct, every bit it volition forestall reordering as well as guarantee visibility.
But the best reply is yous only demand to make bExit as volatile, therefore Thread 2 tin entirely impress “x=1”. x does non demand to live volatile because x cannot live reordered to come upwards after bExit=true when bExit is volatile.
What is deviation betwixt CyclicBarrier as well as CountDownLatch inward Java
Relatively newer Java tricky question, entirely been introduced from Java 5. The master copy deviation betwixt both of them is that yous tin reuse CyclicBarrier fifty-fifty if Barrier is broken, but yous tin non reuse CountDownLatch inward Java. See CyclicBarrier vs CountDownLatch inward Java for to a greater extent than differences.
Question: What does the next Java plan print?
public class Test { public static void main(String[] args) throws Exception { char[] chars = new char[] {'\u0097'}; String str = new String(chars); byte[] bytes = str.getBytes(); System.out.println(Arrays.toString(bytes)); } }
Answer: The trickiness of this enquiry lies on grapheme encoding as well as how String to byte array conversion works. In this program, nosotros are get-go creating a String from a grapheme array, which only has ane grapheme '\u0097', afterward that nosotros are getting the byte array from that String as well as printing that byte. Since \u0097 is within the 8-bit attain of byte primitive type, it is reasonable to guess that the str.getBytes() telephone band volition render a byte array that contains ane chemical component amongst a value of -105 ((byte) 0x97).
However, that's non what the plan prints as well as that's why this enquiry is tricky. As a thing of fact, the output of the plan is operating arrangement as well as locale dependent. On a Windows XP amongst the the U.S. locale, the higher upwards plan prints [63], if yous run this plan on Linux or Solaris, yous volition acquire different values.
To reply this enquiry correctly, yous demand to know virtually how Unicode characters are represented inward Java char values as well as inward Java strings, as well as what role grapheme encoding plays inward String.getBytes().
In elementary word, to convert a string to a byte array, Java iterate through all the characters that the string represents as well as plough each ane into a number of bytes as well as finally position the bytes together. The dominion that maps each Unicode grapheme into a byte array is called a grapheme encoding. So It's possible that if same grapheme encoding is non used during both encoding as well as decoding therefore retrieved value may non live correct. When nosotros call str.getBytes() without specifying a grapheme encoding scheme, the JVM uses the default grapheme encoding of the platform to do the job.
The default encoding system is operating arrangement as well as locale dependent. On Linux, it is UTF-8 as well as on Windows amongst a the U.S. locale, the default encoding is Cp1252. This explains the output nosotros acquire from running this plan on Windows machines amongst a the U.S. locale. No thing which grapheme encoding system is used, Java volition e'er interpret Unicode characters non recognized past times the encoding to 63, which represents the grapheme U+003F (the enquiry mark, ?) inward all encodings.
One to a greater extent than tricky Java questions from the overloading as well as overriding concept. The reply is yous tin really good throw superclass of RuntimeException inward overridden method, but yous tin non do same if its checked Exception. See Rules of method overriding inward Java for to a greater extent than details.
What is the number amongst next implementation of compareTo() method inward Java
public int compareTo(Object o){ Employee emp = (Employee) o; return this.id - e.id; }
where an id is an integer number.
Well, 3 is zilch wrong inward this Java enquiry until yous guarantee that id is e'er positive. This Java enquiry becomes tricky when yous can't guarantee that id is positive or negative. the tricky component subdivision is, If id becomes negative than subtraction may overflow as well as create an wrong result. See How to override compareTo method inward Java for the consummate reply of this Java tricky enquiry for an experienced programmer.
How do yous ensure that due north thread tin access due north resources without deadlock?
If yous are non good versed inward writing multi-threading code therefore this is a existent tricky enquiry for you. This Java enquiry tin live tricky fifty-fifty for the experienced as well as senior programmer, who are non truly exposed to deadlock as well as race conditions. The key indicate hither is ordering, if yous acquire resources inward a exceptional lodge as well as liberate resources inward the contrary lodge yous tin forestall deadlock. See how to avoid deadlock inward Java for a sample code example.
Question: Consider the next Java code snippet, which is initializing 2 variables as well as both are non volatile, and 2 threads T1 as well as T2 are modifying these values every bit following, both are non synchronized
int x = 0; boolean bExit = false; Thread 1 (not synchronized) x = 1; bExit = true; Thread 2 (not synchronized) if (bExit == true) System.out.println("x=" + x);Now tell us, is it possible for Thread 2 to impress “x=0”?
Answer: It's impossible for a listing of tricky Java questions to non incorporate anything from multi-threading. This is the simplest ane I tin get. Answer of this enquiry is Yes, It's possible that thread T2 may impress x=0.Why? because without whatever didactics to compiler e.g. synchronized or volatile, bExit=true might come upwards earlier x=1 inward compiler reordering. Also, x=1 powerfulness non transcend away visible inward Thread 2, therefore Thread 2 volition charge x=0. Now, how do yous ready it?
When I asked this enquiry to a pair of programmers they reply differently, ane suggests to brand both threads synchronized on a mutual mutex, some other ane said brand both variable volatile. Both are correct, every bit it volition forestall reordering as well as guarantee visibility.
But the best reply is yous only demand to make bExit as volatile, therefore Thread 2 tin entirely impress “x=1”. x does non demand to live volatile because x cannot live reordered to come upwards after bExit=true when bExit is volatile.
What is deviation betwixt CyclicBarrier as well as CountDownLatch inward Java
Relatively newer Java tricky question, entirely been introduced from Java 5. The master copy deviation betwixt both of them is that yous tin reuse CyclicBarrier fifty-fifty if Barrier is broken, but yous tin non reuse CountDownLatch inward Java. See CyclicBarrier vs CountDownLatch inward Java for to a greater extent than differences.
What is the deviation betwixt StringBuffer as well as StringBuilder inward Java?
Classic Java questions which some people think tricky as well as some reckon really easy. StringBuilder inward Java was introduced inward JDK 1.5 as well as the entirely deviation betwixt both of them is that StringBuffer methods e.g. length(), capacity() or append() are synchronized acre corresponding methods inward StringBuilder are non synchronized.
Because of this primal difference, concatenation of String using StringBuilder is faster than StringBuffer. Actually, it's considered the bad practise to occupation StringBuffer anymore, because, inward almost 99% scenario, yous perform string concatenation on the same thread. See StringBuilder vs StringBuffer for to a greater extent than differences.
Another tricky Java enquiry from Java fundamentals. No, yous tin non access a non-static variable from the static context inward Java. If yous try, it volition give compile fourth dimension error. This is truly a mutual job beginner inward Java human face upwards when they endeavour to access instance variable within the master copy method. Because master copy is static inward Java, as well as instance variables are non-static, yous tin non access instance variable within main. See, why yous tin non access a non-static variable from static method to larn to a greater extent than virtually this tricky Java questions.
How many String objects are created past times the next code?
Now, it's practise time, hither are some questions for yous guys to answer, these are contributed past times readers of this blog, big thank yous to them.
- When doesn't Singleton rest Singleton inward Java?
- is it possible to charge a course of report past times 2 ClassLoader?
- is it possible for equals() to render false, fifty-fifty if contents of 2 Objects are same?
- Why compareTo() should live consistent to equals() method inward Java?
- When do Double as well as BigDecimal give different answers for equals() as well as compareTo() == 0.
- How does "has before" apply to volatile work?
- Why is 0.1 * 3 != 0.3,
- Why is (Integer) 1 == (Integer) 1 but (Integer) 222 != (Integer) 222 as well as which ascendence arguments alter this.
- What happens when an exception is thrown past times a Thread?
- Difference betwixt notify() as well as notifyAll() call?
- Difference betwixt System.exit() as well as System.halt() method?
- Does next code legal inward Java? is it an instance of method overloading or overriding?
public String getDescription(Object obj){ return obj.toString; } public String getDescription(String obj){ return obj; } as well as public void getDescription(String obj){ return obj; }
This was my listing of Some of the most mutual tricky questions inward Java. It's non a bad thought to fix tricky Java enquiry earlier appearing for whatever meat Java or J2EE interview. One or 2 open-ended or tricky enquiry is quite mutual inward Java interviews.
Further Reading
If yous are looking for super challenging play tricks coding questions therefore yous should depository fiscal establishment check out Joshua Bloch some other classic book, the Java Puzzlers, I am sure yous sick detect them truly challenging to solve, I sure as shooting did.
Hungry for to a greater extent than Java Interview Question as well as Answer post, depository fiscal establishment check out these articles
Further Reading
If yous are looking for super challenging play tricks coding questions therefore yous should depository fiscal establishment check out Joshua Bloch some other classic book, the Java Puzzlers, I am sure yous sick detect them truly challenging to solve, I sure as shooting did.
Hungry for to a greater extent than Java Interview Question as well as Answer post, depository fiscal establishment check out these articles
- 18 Java blueprint pattern enquiry asked inward interviews
- 10 Java coding interview questions reply for 2 to iv years experience
- Top 21 Most Frequently Asked Java Questions as well as Answers
- 133 Core Java Interview Questions from lastly v years
- Top 50 Multithreading as well as Concurrency Interview Questions
- 21 Frequently asked SQL queries from Java Interviews
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