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Q2491. What will be the output of the following code ?
enum Day {
MONDAY,TUESDAY,WEDNESDAY,THURSDAY,FRIDAY,SATURDAY,SUNDAY
}
public class BuggyBread1{
public static void main (String args[]) {
Set mySet = new HashSet();
mySet.add(Day.SATURDAY);
mySet.add(Day.WEDNESDAY);
mySet.add(Day.FRIDAY);
mySet.add(Day.WEDNESDAY);
for(Day d: mySet){
System.out.println(d);
}
}
}
Ans. FRIDAY , SATURDAY and WEDNESDAY will be printed but the order cannot be determined.
Only one FRIDAY will be printed as Set doesn't allow duplicates. Order cannot be determined as HashSet doesn't maintain elements in a particular order.
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If we add Enum constants to a sorted collection ( Treemap , TreeSet ), What will be the order in which they will be maintained ?
Sorted Collection wont maintain them in any order.
Insertion Order
Order in which constants are declared.
Natural Sorting Order.
enums are intrinsically ..
private
public
static
final
Enums cannot be declared ..
private
public
static
final
Q2492. What will be the output of the following code ?
enum Day {
MONDAY,TUESDAY,WEDNESDAY,THURSDAY,FRIDAY,SATURDAY,SUNDAY
}
public class BuggyBread1{
public static void main (String args[]) {
Set mySet = new TreeSet();
mySet.add(Day.SATURDAY);
mySet.add(Day.WEDNESDAY);
mySet.add(Day.FRIDAY);
mySet.add(Day.WEDNESDAY);
for(Day d: mySet){
System.out.println(d);
}
}
}
Only one FRIDAY will be printed as Set doesn't allow duplicates.Elements will be printed in the order in which constants are declared in the Enum. TreeSet maintains the elements in the ascending order which is identified by the defined compareTo method. compareTo method in Enum has been defined such that the constant declared later are greater than the constants declared prior.
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TreeSet maintains the elements in the ascending order which is identified by the compareTo method. compareTo method in String has been defined such that it results in the natural alphabetic Order. Here the elements in the TreeSet are of String and not of Integer. In String Natural Order, 111 comes before 2 as ascii of 1st character first determines the order.
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TreeSet maintains the elements in the ascending order which is identified by the compareTo method. compareTo method in Integer has been defined such that it results in the natural numerical Order.
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Ans. If its already there in Maven local repository, We can add that as a dependency in the project pom file with its Group Id, Artifact Id and version.
We can provide additional attribute SystemPath if its unable to locate the jar in the local repository.
If its not there in the local repository, we can install it first in the local repository and then can add it as dependency.
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Ans. 1. It shouldn't result in infinite loop. Please make sure that you have a condition that will terminate the loop and that condition should be reached.
2. Make sure to use the break statement if you aspire to only look for something. Not using break will unnecessarily execute it till the end of for loop in some cases.
3. Similarly use continue to execute the loop with next iteration and bypass the rest of the code block if required.
4. Try to avoid multiple nesting of for loops. If it''s required, Make sure to use break and continue properly so as to avoid some unnecessary processing.
5. Make sure to use try catch within the loop and not outside the for loop if you expect it to continue if one of the iteration fails.
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LikeDiscussCorrect / Improve java loops continue break for loop control statements loop statement.while loop control statements loop statement architecture
Q2502. Shouldn't we make a class with all static members is its just expected to be executed as a standalone program with just one thread. Moreover Lets assume that there is no runtime Polymorphism required and there is no need for serialization ?
Ans. Still No in case we are making use of inheritance. we may have problem wherein we have program flow moving across common inherited method and specific methods of the derived class. call made to another static method in the parent class will only access the static class of the Parent class irrespective of the call from any of the derived class.
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Ans. AssertionError is actually a fatal fault or a bug in the program. We may not like to continue program , request or thread execution if this error occurs as this condition is the assumption to continue further execution.
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Ans. No, Java runs on a virtual machine called JVM and hence doesn't embed well with the underlying hardware. Though we can create a platform independent system software but that would be really slow and that's what we would never need.
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Q2506. Shall we keep the enumeration name in all capital letters as it contains all constants ?
Ans. Enum is actually a class with pre defined constants. So enum name should follow the convention of the Class name. Though the constant names or the Enum variables should follow the convention of having all capital letters.
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Ans. Static methods can be called using instance references wherein this would have made sense but static method can also be called using Class name wherein this would mean nothing and hence forbidden.
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Methods , Variables , Initialization Blocks and Outer Classes and nested Classes.
Methods , Variables , Initialization Blocks and Outer Classes.
Methods , Variables , Initialization Blocks and nested Classes.
Which of the following cannot be marked static ?
Constructors , Classes ( Outer ) , Classes ( nested ), Interfaces , Local variables , Inner Class methods and instance variables.
Constructors , Classes ( Outer ) , Interfaces , Local variables , Class variables , Class Methods , Inner Class methods and instance variables.
Constructors , Classes ( Outer ) , Interfaces , Local variables , Inner Class methods and instance variables.
Constructors , Classes ( Outer ) , Classes (Nested), Interfaces , Local variables , Inner Class methods and instance variables.
Q2508. In majority of the situations it won't make much sense whether you append this with the instance method call.Can you tell a situation wherein this keyword would make sense in a instance method ?
Ans. Within instance method of the parent class that has other multiple methods that have been overridden by the derived classes.
In such case a simple method call from the common method will always be made to the method definition in the parent class. But If we use this.methodCall , this will be polymorphic and will be made to the respective derived object overriding method.
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Ans. Any reference in java that doesn't point to any object , gets assigned null i.e is a reference to null. Two object references in java are treated equal if they point to the same memory. That's Why null == null results true.
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Ans. Yes, we can substitute outer classes wherever we need to have inner classes but Inner classes have advantage in certain cases and hence preferred -
Ease - Why to implement a class outside if its objects are only intended to be part of an outer object. Its easy to define the class within another class if the use is only local.
Protection - Making a call an outer exposes a threat of it being used by any of the class. Why should it be made an outer class if its object should only occur as part of other objects.
For example - You may like to have an class address whose object should have a reference to city and by design thats the only use of city you have in your application. Making Address and City as outer class exposes City to any of the Class. Making it an inner class of Address will make sure that its accessed using object of Address.
Ans. Its a specification that guides the implementation of ORM frameworks. Implementations abiding by the specification would mean that one can be replaced with other in an application without much hassle. Only the Features that are added over the specification needs to be taken care of if any such change is made.
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Ans. This is an informative annotation that specify that the interface is a functional interface. A Function Interface has only one abstract method and many default methods. Compiler generates an error if the interface specified with the annotation doesn't abide by the specifications for functional interface.
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Ans. Its used to execute last command. Yes this can be used with other string to execute new command. For eg - if ls was the last command, We can execute !! -l for having the long listing.
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Ans. Final variable means a variable that has been declared final and hence cannot be de referenced after initialization. Effective final means a variable that has not been declared final but haven't been reassigned the value after initialization.
First is the regulation that restricts the reassignment and will raise a compilation error if we try to do so. Second is the outcome without the restriction.
Effective Final is the eventual treatment of the variable that is required for many features. For eq - Java 8 requires that local variables referenced from a lambda expression must be final or effectively final.It means all local referenced from lambda expressions must be such that their value shouldn't be changed after initialization whether declared final or not.
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Ans. throw is used to re throw an exception.throws is used to declare that the method throws the respective exceptions.try block is used to identify if the respective block has thrown any exception.catch is used to catch the exception that has been thrown by the respective try block.
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If we add Enum constants to a sorted collection ( Treemap , TreeSet ), What will be the order in which they will be maintained ?
