Q&A

Java interview questions

• why java is platform independent and jvm is platform dependent?
• List any five features of java?
• What all memory areas are allocated by JVM?
• What is difference between JDK, JRE and JVM?
• What is javac?
• Why java is not 100 object oriented language?
• What is the base class of all classes in java?
• What gives java its write once and run anywhere nature?
• What is classloader in java?
• Is empty .java file name a valid source file name?
• Can we overload main() method in java?
• Can we declare main() method as private or protected or with no access modifier?
• Can we declare main method as non static in java?
• Why main() method must be static?
• Can we change return type of main() method?
• Can we run java class without main() method?
• Difference between Object Oriented Programming and Procedural Programming.
• Difference between Object Oriented and Object based language.
• What is class in java?
• What is object in java?
• How to open a notepad in java?
• What is constructor?
• Default constructor
• Does constructor return any value in java?
• Is constructor inherited in java?
• Can you make a constructor final in java?
• Difference between constructor and method in java?
• How to copy values from one object to another java?
• How to overload constructor in java?
• can you create an object without using new operator in java?
• Constructor chaining in java
• Parameterized constructor in java
• Can we call subclass constructor from superclass constructor?
• What happens if you keep return type for a constructor?
• What is the use of private constructor in java?
• Can a constructor call another constructor java?
• What is static variable in java?
• What is static method in java?
• What is static block in java?
• What is this in java?
• What is aggregation in java?
• What is inheritance in java?
• Why multiple inheritance is not supported in java?
• How to implement multiple inheritance in java?
• Are interfaces also inherited from Object class?
• Why an interface cannot have constructor in java?
• How do you restrict a member of a class from inheriting to it’s sub classes?
• Can a class extend itself in java?
• Are constructors inherited in java?
• What happens if both superclass and subclass have a field with same name?
• Are static members inherited to subclasses in java?
• what are access modifiers in java?
• What are different types of access modifiers in java?
• What are non access modifiers in java?
• Can we use abstract and final both with a method?
• Can abstract class have final methods in java?
• Can we declare a class as private in java?
• Can we declare an abstract method as private?
• Can we declare a class as protected in java?
• what is final in java?
• What is final variable in java?
• What is final method in java?
• What is final class in java?
• What is blank final variable in java?
• What is static blank final variable in java?
• What is final parameter in java?
• Can we initialize blank final variable in java?
• Can we declare the main method as final?
• What is the use of final keyword in java?
• Can we change the state of an object to which a final reference variable is pointing?
• Difference between abstract method and final method in java?
• Can we change the value of an interface field?
• Can we declare constructor as final in java?
• What is runtime polymorphism in java?
• Can we achieve runtime polymorphism by data members?
• What is the difference between static binding and dynamic binding in java?
• What is abstraction in java?
• What is the difference between abstraction and encapsulation?
• What is encapsulation in java?
• What is polymorphism in java?
• Are true and false keywords in java?
• Can we declare local inner class as private?
• Is “abc” a primitive value?
• What is the priority of garbage collector thread?
• Is map collection in java?
• Which package is always imported by default?
• Can a class implement two interfaces with the same method signature?
• Can you declare an interface method static in java?
• Which one is faster among string stringbuffer and stringbuilder?
• What is method overloading in java?
• Can we declare an overloaded method as static and another one as non-static?
• Can overloaded methods be synchronized?
• Synchronized override method
• Can we declare overloaded methods as final?
• Can overloaded method be overridden?
• What is method overriding in java?
• Can static method be overridden?
• Difference between method overloading and overriding in java?
• Can we override private methods in java?
• Is it possible to override non static method as static method?
• What is interface in java?
• Can we declare an interface method static in java?
• Can an interface be declared final in java?
• What is marker interface and how we can create it?
• What is difference between abstract class and interface in java?
• What is abstract class in java?
• Why abstract class is used in java?
• Can abstract class have constructors in java?
• Can abstract class be final in java?
• Can we declare local inner class as abstract?
• what is an exception?
• How the exceptions are handled in java?
• What is the difference between error and exception in java?
• Can we keep other statements in between try catch and finally blocks?
• Explain the exception hierarchy in java?
• What are runtime exceptions in java?
• What is outofmemoryerror in java?
• What are checked and unchecked exceptions in java?
• What is the difference between classnotfoundexception and noclassdeffounderror in java?
• Will finally block get executed if return?
• Can we throw an exception without throws?
• What is rethrowing an exception in java?
• What is the use of throws keyword in java?
• What is exception propagation in java?
• Difference between throw and throws in java?
• What is finally in java?
• What is the difference between final finally and finalize in java?
• How to create customized exceptions in java?
• What is classcastexception in java?
• What is stackoverflowerror in java?
• What is the superclass of all exception classes?
• What is the use of printstacktrace method in java?
• What is arraystoreexception in java?
• Why string objects are immutable in java?
• How many ways we can create the string object?
• Why java uses the concept of string literal?
• String vs StringBuffer vs StringBuilder in java
• How to create immutable class in java?
• What is the purpose of toString() method in java?
• Is string a keyword in java?
• Is string a primitive type or derived type?
• What is string constant pool in java?
• What are mutable and immutable objects in java?
• What is string intern in java?
• Can we call string class methods using string literals?
• Can we change array size in java?
• What is an anonymous array in java?
• Difference between array and arraylist in java?
• What are jagged arrays in java?
• Can array size be negative in java?
• Java program to find duplicate elements in an array.
• Java program to find second largest element in an array of integers.
• Java program to check the equality of two arrays.
• Find all pairs of elements in an integer array whose sum is equal to a given number.
• Java program to find continuous sub array whose sum is equal to a given number
• Java program to find the intersection of two arrays
• Java program to separate zeros from non-zeros in an integer array
• Java program to find all the leaders in an integer array
• Java program to find a missing number in an integer array
• Java program to convert an array to ArrayList and an ArrayList to array
• Java program to count occurrences of each element in an array
• Java program to reverse an array without using an additional array
• Java program to remove duplicate elements from an array
• Java program to find union and intersection of multiple arrays
• Java program to find the most frequent element in an array
• What is multithreading?
• Difference between process and thread in java?
• What is thread in java?
• What is join method in java?
• What is the difference between sleep and yield method?
• Is it possible to start a thread twice in java?
• Can we call run method directly in java?
• What is daemon threads in java?
• Can we make the user thread as daemon thread if thread is started?
• Difference between thread start and run method.
• Why we call start method in thread?
• Which is a better way to create a thread in java?
• Can we override start method?
• Can we override run method?
• How to get current thread in java?
• What is synchronization?
• What is synchronized block in java?
• What is synchronized method in java?
• What is static synchronization in java?
• What is deadlock in java?
• What is starvation in java?
• ArrayList vs LinkedList vs Vector
• Iterator vs ListIterator vs Enumeration
• List vs Set Vs Map
• HashSet vs LinkedHashSet vs TreeSet
• HashMap vs LinkedHashMap vs TreeMap vs HashTable
• HashSet vs HashMap vs HashTable
• Collection vs collections in java
• Comparable vs Comparator interfaces
• What is garbage collection in java?
• What is garbage collector in java?
• Can an unreferenced objects be referenced again in java?
• What kind of thread is the garbage collector thread in java?
• what is serialization in java?
• what is Deserialization in java?
• What is transient keyword?
• Java hashcode and equals methods
• How HashMep works internally?
• How hashmap stores null key?
• How hashset works internally?