What is a tricky question? Well, tricky Java interview questions are those questions which receive got some surprise chemical cistron on it. If you lot endeavour to reply a tricky enquiry amongst mutual sense, you lot volition most probable neglect because they require some specific knowledge. Most of the tricky Java questions comes from confusing concepts similar business office overloading as well as overriding, Multi-threading which is genuinely 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 you lot don't know the answer. Anyway inwards 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 noesis of Java programming linguistic communication to reply them correctly. As per my experience, at that spot is ever 1 or 2 tricky or tough Java interview question on whatever heart Java or J2EE interviews, thence it's expert to laid tricky questions from Java inwards advance.
If I accept an interview, I purposefully set this sort of enquiry to guess the depth of candidate's agreement inwards Java. Another wages of shout out for such enquiry is the surprising element, which is a key cistron to set the candidate on some line per unit of measurement area during interviews.
If I accept an interview, I purposefully set this sort of enquiry to guess the depth of candidate's agreement inwards Java. Another wages of shout out for such enquiry is the surprising element, which is a key cistron to set the candidate on some line per unit of measurement area during interviews.
Since these questions are less common, at that spot is expert gamble that many Java developer doesn't know almost it. You won't notice these questions fifty-fifty on pop Java interview books similar Java Programming Interview exposed, which is withal an fantabulous conduct for Java interviews.
Btw, if you lot don't notice these enquiry tricky enough, as well as thence you lot should cheque Joshua Bloch's some other classic book, Java Puzzlers for super tricky questions. I am sure you lot volition notice them challenging enough.
What volition hap if you lot set render declaration or System.exit () on endeavour or select grip of block? Will finally block execute?
This is a rattling pop tricky Java enquiry as well as it's tricky because many programmers think that no thing what, but the finally block volition ever execute. This enquiry challenge that concept past times putting a render declaration inwards the endeavour or select grip of block or calling System.exit() from endeavour or select grip of block. Answer of this tricky enquiry inwards Java is that finally block volition execute fifty-fifty if you lot set a render declaration inwards the endeavour block or select grip of block but finally block won't run if you lot telephone phone System.exit() from endeavour or select grip of block.
Question: Can you lot override a person or static method inwards Java?
Another pop Java tricky question, As I said method overriding is a expert theme to enquire fox questions inwards Java. Anyway, you tin non override a person or static method inwards Java, if you lot create a similar method amongst same render type as well as same method arguments inwards tyke shape as well as thence it volition enshroud the superclass method, this is known equally method hiding.
What is the deviation betwixt StringBuffer as well as StringBuilder inwards Java?
Classic Java questions which some people think tricky as well as some visit rattling easy. StringBuilder inwards Java was introduced inwards JDK 1.5 as well as the exclusively deviation betwixt both of them is that StringBuffer methods e.g. length(), capacity() or append() are synchronized spell corresponding methods inwards StringBuilder are non synchronized.
Because of this key difference, concatenation of String using StringBuilder is faster than StringBuffer. Actually, it's considered the bad exercise to utilisation StringBuffer anymore, because, inwards almost 99% scenario, you lot perform string concatenation on the same thread. See StringBuilder vs StringBuffer for to a greater extent than differences.
Can you lot access a non-static variable inwards the static context?
Another tricky Java enquiry from Java fundamentals. No, you lot tin non access a non-static variable from the static context inwards Java. If you lot try, it volition laissez passer on compile fourth dimension error. This is genuinely a mutual work beginner inwards Java confront when they endeavour to access illustration variable within the brain method. Because brain is static inwards Java, as well as illustration variables are non-static, you lot tin non access illustration variable within main. See, why you lot tin non access a non-static variable from static method to larn to a greater extent than almost this tricky Java questions.
How many String objects are created past times the next code?
Now, it's exercise time, hither are some questions for you lot guys to answer, these are contributed past times readers of this blog, big cheers to them.
Btw, if you lot don't notice these enquiry tricky enough, as well as thence you lot should cheque Joshua Bloch's some other classic book, Java Puzzlers for super tricky questions. I am sure you lot volition notice them challenging enough.
10 Tricky Java interview enquiry - Answered
Here is my listing of 10 tricky Java interview questions, Though I receive got prepared as well as shared lot of hard heart Java interview enquiry as well as answers, But I receive got chosen them equally Top 10 tricky questions because you lot tin non guess answers of this tricky Java questions easily, you lot 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 different the Integer, where MIN_VALUE is negative, both the MAX_VALUE as well as MIN_VALUE of the Double shape are positive numbers. The Double.MIN_VALUE is 2^(-1074), a double constant whose magnitude is the to the lowest degree amidst all double values. So different the obvious answer, this plan volition impress 0.0 because Double.MIN_VALUE is greater than 0. I receive got asked this enquiry to Java developer having sense upward to 3 to five years as well as surprisingly almost 70% candidate got it wrong.
What volition hap if you lot set render declaration or System.exit () on endeavour or select grip of block? Will finally block execute?
This is a rattling pop tricky Java enquiry as well as it's tricky because many programmers think that no thing what, but the finally block volition ever execute. This enquiry challenge that concept past times putting a render declaration inwards the endeavour or select grip of block or calling System.exit() from endeavour or select grip of block. Answer of this tricky enquiry inwards Java is that finally block volition execute fifty-fifty if you lot set a render declaration inwards the endeavour block or select grip of block but finally block won't run if you lot telephone phone System.exit() from endeavour or select grip of block.
Another pop Java tricky question, As I said method overriding is a expert theme to enquire fox questions inwards Java. Anyway, you tin non override a person or static method inwards Java, if you lot create a similar method amongst same render type as well as same method arguments inwards tyke shape as well as thence it volition enshroud the superclass method, this is known equally method hiding.
Similarly, you lot cannot override a person method inwards sub shape because it's non accessible there, what you lot do is create some other person method amongst the same mention inwards the tyke class. See Can you lot override a person method inwards Java or to a greater extent than details.
Question: What do the aspect 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 almost the double primitive type as well as Double class, spell doing floating signal 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 uncomplicated reply to this enquiry is that it volition non throw ArithmeticExcpetion as well as render Double.INFINITY.
Also, Federal Reserve notation that the comparing x == Double.NaN ever evaluates to false, fifty-fifty if x itself is a NaN. To examine if x is a NaN, 1 should utilisation the method telephone phone Double.isNaN(x) to cheque if given number is NaN or not. If you lot know SQL, this is rattling to a greater extent than or less NULL there.
Btw, If you lot are running out of fourth dimension for your interview preparation, you lot tin likewise cheque out Java Programming Interviews exposed for to a greater extent than of such pop questions,
Does Java back upward multiple inheritances?
This is the trickiest enquiry inwards Java if C++ tin back upward straight multiple inheritances than why non Java is the declaration Interviewer often give. Answer of this enquiry is much to a greater extent than subtle as well as thence it looks like, because Java does back upward multiple inheritances of Type past times allowing an interface to extend other interfaces, what Java doesn't back upward is multiple inheritances of implementation. This distinction likewise gets blur because of default method of Java 8, which straight off provides Java, multiple inheritances of demeanor equally well. See why multiple inheritances are non supported inwards Java to reply this tricky Java question.
What volition hap if nosotros set a key object inwards a HashMap which is already there?
This tricky Java enquiry is portion of some other ofttimes asked question, How HashMap industrial plant inwards Java. HashMap is likewise a pop theme to create confusing as well as tricky enquiry inwards Java. Answer of this enquiry is if you lot set the same key 1 time to a greater extent than as well as thence it volition supersede the onetime mapping because HashMap doesn't allow duplicate keys. The Same key volition lawsuit inwards the same hashcode as well as volition cease upward at the same seat inwards the bucket.
Question: What do the aspect 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 almost the double primitive type as well as Double class, spell doing floating signal 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 uncomplicated reply to this enquiry is that it volition non throw ArithmeticExcpetion as well as render Double.INFINITY.
Also, Federal Reserve notation that the comparing x == Double.NaN ever evaluates to false, fifty-fifty if x itself is a NaN. To examine if x is a NaN, 1 should utilisation the method telephone phone Double.isNaN(x) to cheque if given number is NaN or not. If you lot know SQL, this is rattling to a greater extent than or less NULL there.
Btw, If you lot are running out of fourth dimension for your interview preparation, you lot tin likewise cheque out Java Programming Interviews exposed for to a greater extent than of such pop questions,
This is the trickiest enquiry inwards Java if C++ tin back upward straight multiple inheritances than why non Java is the declaration Interviewer often give. Answer of this enquiry is much to a greater extent than subtle as well as thence it looks like, because Java does back upward multiple inheritances of Type past times allowing an interface to extend other interfaces, what Java doesn't back upward is multiple inheritances of implementation. This distinction likewise gets blur because of default method of Java 8, which straight off provides Java, multiple inheritances of demeanor equally well. See why multiple inheritances are non supported inwards Java to reply this tricky Java question.
This tricky Java enquiry is portion of some other ofttimes asked question, How HashMap industrial plant inwards Java. HashMap is likewise a pop theme to create confusing as well as tricky enquiry inwards Java. Answer of this enquiry is if you lot set the same key 1 time to a greater extent than as well as thence it volition supersede the onetime mapping because HashMap doesn't allow duplicate keys. The Same key volition lawsuit inwards the same hashcode as well as volition cease upward at the same seat inwards the bucket.
Each bucket contains a linked listing of Map.Entry object, which contains both Key as well as Value. Now Java volition accept the Key object from each entry as well as compare amongst this novel key using equals() method, if that render truthful as well as thence value object inwards that entry volition live replaced past times novel value. See How HashMap industrial plant inwards 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 kickoff creating a String from a grapheme array, which merely has 1 grapheme '\u0097', subsequently 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 phone volition render a byte array that contains 1 chemical cistron 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 organisation as well as locale dependent. On a Windows XP amongst the United States locale, the higher upward plan prints [63], if you lot run this plan on Linux or Solaris, you lot volition acquire different values.
To reply this enquiry correctly, you lot demand to know almost how Unicode characters are represented inwards Java char values as well as inwards Java strings, as well as what role grapheme encoding plays inwards String.getBytes().
In uncomplicated word, to convert a string to a byte array, Java iterate through all the characters that the string represents as well as plough each 1 into a number of bytes as well as finally set 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 as well as thence 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 organisation as well as locale dependent. On Linux, it is UTF-8 as well as on Windows amongst a United States locale, the default encoding is Cp1252. This explains the output nosotros acquire from running this plan on Windows machines amongst a United States locale. No thing which grapheme encoding system is used, Java volition ever interpret Unicode characters non recognized past times the encoding to 63, which represents the grapheme U+003F (the enquiry mark, ?) inwards all encodings.
If a method throws NullPointerException inwards 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 you lot tin rattling good throw superclass of RuntimeException inwards overridden method, but you lot tin non do same if its checked Exception. See Rules of method overriding inwards Java for to a greater extent than details.
How do you lot ensure that northward thread tin access northward resources without deadlock?
If you lot are non good versed inwards writing multi-threading code as well as thence 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 genuinely exposed to deadlock as well as race conditions. The key signal hither is ordering, if you lot acquire resources inwards a exceptional social club as well as unloose resources inwards the contrary social club you lot tin preclude deadlock. See how to avoid deadlock inwards 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 equally 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 1 I tin get. Answer of this enquiry is Yes, It's possible that thread T2 may impress x=0.Why? because without whatever teaching to compiler e.g. synchronized or volatile, bExit=true might come upward earlier x=1 inwards compiler reordering. Also, x=1 powerfulness non acquire visible inwards Thread 2, thence Thread 2 volition charge x=0. Now, how do you lot ready it?
When I asked this enquiry to a twain of programmers they reply differently, 1 suggests to brand both threads synchronized on a mutual mutex, some other 1 said brand both variable volatile. Both are correct, equally it volition preclude reordering as well as guarantee visibility.
But the best reply is you lot merely demand to make bExit as volatile, as well as thence Thread 2 tin exclusively impress “x=1”. x does non demand to live volatile because x cannot live reordered to come upward after bExit=true when bExit is volatile.
What is deviation betwixt CyclicBarrier as well as CountDownLatch inwards Java
Relatively newer Java tricky question, exclusively been introduced from Java 5. The brain deviation betwixt both of them is that you lot tin reuse CyclicBarrier fifty-fifty if Barrier is broken, but you lot tin non reuse CountDownLatch inwards Java. See CyclicBarrier vs CountDownLatch inwards 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 kickoff creating a String from a grapheme array, which merely has 1 grapheme '\u0097', subsequently 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 phone volition render a byte array that contains 1 chemical cistron 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 organisation as well as locale dependent. On a Windows XP amongst the United States locale, the higher upward plan prints [63], if you lot run this plan on Linux or Solaris, you lot volition acquire different values.
To reply this enquiry correctly, you lot demand to know almost how Unicode characters are represented inwards Java char values as well as inwards Java strings, as well as what role grapheme encoding plays inwards String.getBytes().
In uncomplicated word, to convert a string to a byte array, Java iterate through all the characters that the string represents as well as plough each 1 into a number of bytes as well as finally set 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 as well as thence 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 organisation as well as locale dependent. On Linux, it is UTF-8 as well as on Windows amongst a United States locale, the default encoding is Cp1252. This explains the output nosotros acquire from running this plan on Windows machines amongst a United States locale. No thing which grapheme encoding system is used, Java volition ever interpret Unicode characters non recognized past times the encoding to 63, which represents the grapheme U+003F (the enquiry mark, ?) inwards all encodings.
One to a greater extent than tricky Java questions from the overloading as well as overriding concept. The reply is you lot tin rattling good throw superclass of RuntimeException inwards overridden method, but you lot tin non do same if its checked Exception. See Rules of method overriding inwards Java for to a greater extent than details.
What is the number amongst next implementation of compareTo() method inwards 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 zippo wrong inwards this Java enquiry until you lot guarantee that id is ever positive. This Java enquiry becomes tricky when you lot can't guarantee that id is positive or negative. the tricky portion is, If id becomes negative than subtraction may overflow as well as make an wrong result. See How to override compareTo method inwards Java for the consummate reply of this Java tricky enquiry for an experienced programmer.
How do you lot ensure that northward thread tin access northward resources without deadlock?
If you lot are non good versed inwards writing multi-threading code as well as thence 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 genuinely exposed to deadlock as well as race conditions. The key signal hither is ordering, if you lot acquire resources inwards a exceptional social club as well as unloose resources inwards the contrary social club you lot tin preclude deadlock. See how to avoid deadlock inwards 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 equally 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 1 I tin get. Answer of this enquiry is Yes, It's possible that thread T2 may impress x=0.Why? because without whatever teaching to compiler e.g. synchronized or volatile, bExit=true might come upward earlier x=1 inwards compiler reordering. Also, x=1 powerfulness non acquire visible inwards Thread 2, thence Thread 2 volition charge x=0. Now, how do you lot ready it?
When I asked this enquiry to a twain of programmers they reply differently, 1 suggests to brand both threads synchronized on a mutual mutex, some other 1 said brand both variable volatile. Both are correct, equally it volition preclude reordering as well as guarantee visibility.
But the best reply is you lot merely demand to make bExit as volatile, as well as thence Thread 2 tin exclusively impress “x=1”. x does non demand to live volatile because x cannot live reordered to come upward after bExit=true when bExit is volatile.
What is deviation betwixt CyclicBarrier as well as CountDownLatch inwards Java
Relatively newer Java tricky question, exclusively been introduced from Java 5. The brain deviation betwixt both of them is that you lot tin reuse CyclicBarrier fifty-fifty if Barrier is broken, but you lot tin non reuse CountDownLatch inwards Java. See CyclicBarrier vs CountDownLatch inwards Java for to a greater extent than differences.
What is the deviation betwixt StringBuffer as well as StringBuilder inwards Java?
Classic Java questions which some people think tricky as well as some visit rattling easy. StringBuilder inwards Java was introduced inwards JDK 1.5 as well as the exclusively deviation betwixt both of them is that StringBuffer methods e.g. length(), capacity() or append() are synchronized spell corresponding methods inwards StringBuilder are non synchronized.
Because of this key difference, concatenation of String using StringBuilder is faster than StringBuffer. Actually, it's considered the bad exercise to utilisation StringBuffer anymore, because, inwards almost 99% scenario, you lot 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, you lot tin non access a non-static variable from the static context inwards Java. If you lot try, it volition laissez passer on compile fourth dimension error. This is genuinely a mutual work beginner inwards Java confront when they endeavour to access illustration variable within the brain method. Because brain is static inwards Java, as well as illustration variables are non-static, you lot tin non access illustration variable within main. See, why you lot tin non access a non-static variable from static method to larn to a greater extent than almost this tricky Java questions.
How many String objects are created past times the next code?
Now, it's exercise time, hither are some questions for you lot guys to answer, these are contributed past times readers of this blog, big cheers to them.
- When doesn't Singleton rest Singleton inwards Java?
- is it possible to charge a shape 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 inwards Java?
- When do Double as well as BigDecimal laissez passer on 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 ascendancy 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 inwards Java? is it an illustration 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 inwards Java. It's non a bad thought to laid tricky Java enquiry earlier appearing for whatever heart Java or J2EE interview. One or 2 open-ended or tricky enquiry is quite mutual inwards Java interviews.
Further Reading
If you lot are looking for super challenging fox coding questions as well as thence you lot should cheque out Joshua Bloch some other classic book, the Java Puzzlers, I am sure you lot sick notice them genuinely challenging to solve, I surely did.
Hungry for to a greater extent than Java Interview Question as well as Answer post, cheque out these articles
Further Reading
If you lot are looking for super challenging fox coding questions as well as thence you lot should cheque out Joshua Bloch some other classic book, the Java Puzzlers, I am sure you lot sick notice them genuinely challenging to solve, I surely did.
Hungry for to a greater extent than Java Interview Question as well as Answer post, cheque out these articles
- 18 Java pattern pattern enquiry asked inwards 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 five years
- Top 50 Multithreading as well as Concurrency Interview Questions
- 21 Frequently asked SQL queries from Java Interviews
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