What is the difference between iterator access and index access?
Index based access allow access of the element directly on the basis of index The cursor of the datastructure can directly go to the 'n' location and get the element.
In Iterator based access, the cursor has to traverse through each element to get the desired element.
Insertion, updation or deletion will be faster for index based access if the operations are performed on elements present at at last of the datastructure.
Insertion, updation or deletion will be faster for iterator based access if the operations are performed on elements present in between the datastructure
Insertion, updation or deletion will be faster for iterator based access if the operations are performed on elements present at at last of the datastructure.
Insertion, updation or deletion will be faster for index based access if the operations are performed on elements present in between the datastructure
ArrayList is index access and LinkedList is iterator access
ArrayList is iterator access and LinkedList is index access
How to sort a list in reverse order?
List list = new ArrayList(); Comparator comp = Collections.reverseOrder(); Collections.sort(list, comp)
List list = new ArrayList(); Collections.sort(list, comp)
List list = new ArrayList(); Comparator comp = Collections.reverseOrder(); Collections.sortReverse(list, comp)
Can a null element be added to a TreeSet or HashSet?
How to sort list of strings - case sensitive?
Collections.sort(list,String.CASE_INSENSITIVE_ORDER);
Collections.sort(list,String.CASE_SENSITIVE_ORDER);
Collections.sort(list,String.SENSITIVE_ORDER);
How to make a list unmodifiable (ArrayList, Vector, LinkedList)
Collections.unmodifiableList(list)
Collections.readOnly(list)
Collections.nonmodifiable(list)
Is a thread-safe implementation of Map Interface. In this class put and remove method are synchronized but not the get method. Better than HashTable in terms of performance
ConcurrentHashMap
LinkedHashSet
Which is faster to iterate LinkedHashSet or LinkedList?
LinkedList
Which data structure HashSet Implements?
Implements hashmap internally to store the data
Implements linkedlist internally to store the data
What is identityHashMap?
Uses == for equality checking instead of equals()
Uses equals() for equality checking instead of ==
What is an exception?
Is said to be thrown whenever an exceptional event occurs in java which signals that something is not correct with the code written an may give unexpected results.
Is said to be thrown whenever an exceptional event occurs in java which signals that something is not correct with the code written an may expected results.
Exceptions are defined in which java package?
All the exceptions are subclasses of java.lang.Exception
All the exceptions are subclasses of java.lang.com.Exception
Try-catch-finally block is...
The way java handles exceptions
a form of iteration between collections
Characteristics of Runtime Exception
represent problems that are the result of a programming problem. Such problems include arithmetic exceptions, such as dividing by zero; pointer exceptions: such as trying to access an object through a null reference; and indexing exceptions: such as attempting to access an array element through an index that is too large or too small.
exceptions need not be explicitly caught in try catch block as it can occur anywhere in a program, and in a typical one they can be very numerous.
exceptions which forces the programmer to catch them explicitly in try-catch block.
is called also unchecked exception
What is the difference between error and exception?
An error is an irrecoverable condition occurring at runtime. Such as OutOfMemory error. The application will come to a halt and is not recoverable
An exception is an irrecoverable condition occurring at runtime. Such as OutOfMemory error. The application will come to a halt and is not recoverable
Exceptions are conditions that occur because of bad input or human error. Like a FileNotFoundException or a NullPointerException. In most of these cases its possible to recover from an exception (probably by giving user a feedback for entering proper values etc.)
Errors are conditions that occur because of bad input or human error. Like a FileNotFoundException or a NullPointerException. In most of these cases its possible to recover from an exception (probably by giving user a feedback for entering proper values etc.)
What is ClassNotFoundException?
Is thrown when the reported class isnot found by the ClassLoader in the CLASSPATH
Is thrown when the calss in question has static blocks or members which use a Class that is not found in the ClassLoader
What is NoClassDefFoundError?
Is thrown when the reported class is not found by the ClassLoader in the CLASSPATH
Is thrown when the class in question has static blocks or members which use a class that is not found by the ClassLoader
Is used to throw the exception manually
throw keyword
try-catch block
What is the use of throws keyword?
if the function is not capable of handling the exception then it can ask the calling method to handle the exception
It is used to throw the exception manually
How to create custom exceptions?
Extend the exception class or any of its subclasses
Override methods from the Exception class of your preference.
When to make a custom checked Exception?
If the application can recover from an exception
If the application cant do nothing to recover from the exception
When to make an unchecked exception?
When the application can do something to recover from an exception
When the applications can not do anything to recover from an exception
What is a StackOverflowError?
Is an Error Object thrown by the Runtime System when it Encounters that your application/code has ran out of memory. It may occur in case of recursive methods or a large amount of data is fetched from the server and stored in some object. This error is generated by JVM
Is an Error Object thrown by the Runtime System when it Encounters that your application/code has ran out of memory. It does not may occur in case of recursive methods or a small amount of data is fetched from the server and stored in some object. This error is generated by JVM
Once the control reaches the catch block does it returns back to the try block?
What is the purpose of the finally block?
If an exception is or is not thrown the finally block is reached and there you can tipically release connections, closing of result, etc.
Be executed just if an exception is thrown
Finalize the actions of the code no matter what action was performed in the try-catch block
Is valid to have a try block without catch or finally?
Yes, the try block is the only thing that matters
No. This will result in a compilation error
No. The try block must be followed by a catch or a finally block
What is the method that allows to print the descriptive information about the exception ocurred during the program execution?
printStackTrace()
println()
print()
Is a good practice to write a single catch all handler to catch all the exceptions?
No, If you use the Superclass Exception in the catch block you will not receive valuable information about each of the exception thrown during the execution. All so it will increase the difficutly to read the code since you are not gonna know what is the exact reason of the try-catch
Yes, because you will save lines of code if you do not write all those try-catch blocks
What is exception matching?
is the process by which the jvm finds out the matching catch block for the exception thrown from the list of catch blocks
is the process where the JVM matchs blocks of try catch to use the best
How the exceptions must be placed in a try catch block? (because if are handled incorrectly it will result in a compilation error)
Most specific exceptions must always be placed above the catch block written to handle more general exceptions
More general exceptions must always be placed above the catch block written to handle more specific exceptions
If the exceptions are siblings in the Exception class's hierarchy when placed in multiple catch block, does it matter in what position are placed?
No, if they are not subtypes or supertypes of each other
Yes, always the more specific exception must be caught first
What does Ducking the exception mean?
If a method does not throw directly a checked exception but calls a method that does that and that method declares the exception but is not handled, then the calling method must handle the exception using throws.
Is a type of exception that happens only when the exception is rethrown again in the same catch block
