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Java Interview Questions and Answers | Spring and Hibernate Interview Questions | Java Tutorial | Edureka

This Edureka Java Interview Questions and Answers tutorial will help you to prepare yourself for Java Interviews ( Java Interview Questions Blog: https://goo.gl/GY3yTR ). Learn about the most important Java interview questions and answers and know what will set you apart in the interview process. <br><br>This tutorial covers Java Interview Questions on: <br>1) Basic Java Questions <br>2) OOPS Questions <br>3) Servlets <br>4) JDBC <br>5) Spring <br>6) Hibernate

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Java Interview Questions and Answers | Spring and Hibernate Interview Questions | Java Tutorial | Edureka

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  1. https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  2. Java Market ➢ Java has been rated #1 in TIOBE Popular programming languages index. ➢ Used by 10 Million developers world wide to develop applications for the 15 Billion devices supporting Java. ➢ Used for creating applications for trending technologies like Big Data to household devices like Mobiles and DTH boxes, Java is used everywhere. https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  3. Java Job Trends Below are the number for job postings for Java professionals on various job portals as on 15thMarch 2017. https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  4. Java Job Distribution and Salary Trends Below are the overall Job Distribution and Average salary trends in the Java Domain as on 15thJanuary 2017. https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  5. Agenda For Today Basic Java Questions OOPS Questions Servlets JDBC Spring Hibernate https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  6. OOPS JDBC Hibernate Spring Servlets Basic Questions

  7. Java Interview Questions Q1. What is difference between JDK,JRE and JVM? https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  8. Java Interview Questions Q1. What is difference between JDK,JRE and JVM? JVM (Java Virtual Machine) is an abstract machine. It is a specification that provides runtime environment in which java bytecode can be executed. JDK JRE JRE (Java Runtime Environment) is a runtime environment which implements JVM and provides all class libraries and other files that JVM uses at runtime. JVM JDK(Java Development Kit) is the tool necessary to compile, document and package Java programs. The JDK completely includes JRE. https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  9. Java Interview Questions Q2. What is synchronization? https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  10. Java Interview Questions Q2. What is synchronization? ➢ Synchronization is a process which keeps all concurrent threads in execution to be in sync. ➢ Synchronization avoids memory consistency errors caused due to inconsistent view of shared memory. https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  11. Java Interview Questions Q3. What are the differences between processes and threads? https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  12. Java Interview Questions Q3. What are the differences between processes and threads? Process Thread An executing instance of a program is called a process. Definition A thread is a subset of the process. Processes must use inter-process communication to communicate with sibling processes. Threads can directly communicate with other threads of its process. Communication Processes can only exercise control over child processes. Threads can exercise considerable control over threads of the same process. Control Any change in the parent process does not affect child processes. Any change in the main thread may affect the behavior of the other threads of the process. Changes Memory Run in separate memory spaces. Run in shared memory spaces. Threads are controlled by programmer in a program. Controlled by Process is controlled by the operating system. Dependence Processes are independent. Threads are dependent. https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  13. Java Interview Questions Q4. What are Wrapper classes? https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  14. Java Interview Questions Q4. What are Wrapper classes? Each of Java's eight primitive data types has a class dedicated to it. These are known as wrapper classes because they "wrap" the primitive data type into an object of that class Primitive Wrapper Class Constructor Argument boolean Boolean boolean or String byte Byte byte or String char Character char int Integer int or String float Float float, double or String double Double double or String long Long long or String short Short short or String https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  15. Java Interview Questions Q5. What purpose does the keywords final, finally, and finalize fulfill? https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  16. Java Interview Questions Q5. What purpose does the keywords final, finally, and finalize fulfill? final finally finalize ➢ Finalize is used to perform clean up processing just before object is garbage collected. ➢ Final is used to apply restrictions on class, method and variable. ➢ Final class can't be inherited, final method can't be overridden and final variable value can't be changed. ➢ Finally is used to place important code, it will be executed whether exception is handled or not. https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  17. Java Interview Questions Q6. What is the difference between StringBuffer and StringBuilder? https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  18. Java Interview Questions Q6. What is the difference between StringBuffer and StringBuilder? ➢ StringBuffer operations are thread-safe and synchronized where StringBuilder operations are not thread-safe. ➢ StringBuffer is to be used when multiple threads are working on same String and StringBuilder in the single threaded environment. ➢ StringBuilder performance is faster when compared to StringBuffer because of no overhead of synchronized https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  19. Java Interview Questions Q7. What are the differences between Heap and Stack Memory? https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  20. Java Interview Questions Q7. What are the differences between Heap and Stack Memory? Stack Heap Stack memory is used only by one thread of execution. Heap memory is used by all the parts of the application. Memory Objects stored in the heap are globally accessible Stack memory can’t be accessed by other threads. Access Memory Management Memory management is based on generation associated to each object. Follows LIFO manner to free memory. Exists until the end of execution of the tread. Heap memory lives from the start till the end of application execution. Lifetime Stack memory only contains local primitive variables and reference variables to objects in heap space. Whenever an object is created, it’s always stored in the Heap space Usage https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  21. Java Interview Questions Q8. What is the difference between Arrylist and Vector? https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  22. Java Interview Questions Q8. What is the difference between Arrylist and Vector? Array List Vector Array List is not synchronized. Vector is synchronized. Array List is fast as it’s non-synchronized Vector is slow as it is thread safe. If an element is inserted into the Array List, it increases its Array size by 50%. Vector defaults to doubling size of its array. Array List does not define the increment size. Vector defines the increment size. Array List can only use Iterator for traversing an Array List. Except Hashtable, Vector is the only other class which uses both Enumeration and Iterator. https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  23. Java Interview Questions Q9. What is the difference between HashMap and HashTable https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  24. Java Interview Questions Q9. What is the difference between HashMap and HashTable HashMap HashTable HashMap is non synchronized and are not- thread safe. Hashtable is synchronized. It is thread-safe and can be shared with many threads. HashMap allows one null key and multiple null values. Hashtable doesn't allow any null key or value. HashMap is fast compared to HashTable Hashtable is slow compared to HashMap We can make the HashMap as synchronized by calling Collections.synchronizedMap(hashMap) Hashtable is internally synchronized and can't be unsynchronized. HashMap is traversed by Iterator. Hashtable is traversed by Enumerator and Iterator. HashMap inherits AbstractMap class. Hashtable inherits Dictionary class. https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  25. Java Interview Questions Q10. What is the difference between equals() and == operator ? https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  26. Java Interview Questions Q10. What is the difference between equals() and == operator ? ➢ Equals() method is defined in Object class in Java and used for checking equality of two objects defined by business logic. ➢ "==" or equality operator in Java is a binary operator provided by Java programming language and used to compare primitives and objects. https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  27. Java Interview Questions Q11. What will be the output of this program? https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  28. Java Interview Questions Q11. What will be the output of this program? Output: 11 https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  29. OOPS Questions Hibernate JDBC Servlets Basic Questions Spring

  30. Java Interview Questions Q12. What is the difference between Abstract classes and Interfaces? https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  31. Java Interview Questions Q12. What is the difference between Abstract classes and Interfaces? Abstract Class Interfaces An abstract class can provide complete, default code and/or just the details that have to be overridden. In case of abstract class, a class may extend only one abstract class. An abstract class can have non-abstract methods. An abstract class can have instance variables. An abstract class can have any visibility: public, private, protected. An abstract class can contain constructors . An interface cannot provide any code at all,just the signature. A Class may implement several interfaces. All methods of an Interface are abstract. An Interface cannot have instance variables. An Interface visibility must be public (or) none. An Interface cannot contain constructors . Interfaces are slow as it requires extra indirection to find corresponding method in the actual class. Abstract classes are fast. https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  32. Java Interview Questions Q13. What is Polymorphism? https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  33. Java Interview Questions Q13. What is Polymorphism? Mobile ➢ Polymorphism is briefly described as “one interface, many implementations”. ➢ It is a characteristic of being able to assign a different meaning or usage to something in different contexts. MP3 Player Camera Remote https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  34. Java Interview Questions Q14. What is runtime polymorphism or dynamic method dispatch? https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  35. Java Interview Questions Q14. What is runtime polymorphism or dynamic method dispatch? ➢ It is a process in which a call to an overridden method is resolved at runtime rather than at compile-time. ➢ In this process, an overridden method is called through the reference variable of a superclass. ➢ The determination of the method to be called is based on the object being referred to by the reference variable. https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  36. Java Interview Questions Q15. What is the difference between method overloading and method overriding? https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  37. Java Interview Questions Q15. What is the difference between method overloading and method overriding? Overloaded Method Overridden Method In Method Overloading, Methods of the same class shares the same name but each method must have different number of parameters or parameters having different types and order. In Method Overriding, sub class have the same method with same name and exactly the same number and type of parameters and same return type as a super class. Definition Method Overloading is to “add” or “extend” more to method’s behavior. Method Overriding is to “Change” existing behavior of method. Behavior Polymorphism It is a compile time polymorphism. It is a run time polymorphism. Signature The methods must have different signature. The methods must have same signature. It may or may not need inheritance in Method Overloading. It always requires inheritance in Method Overriding. Inheritance https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  38. Java Interview Questions Q15. What is the difference between Method overloading and Method overriding? Method overloading Method overriding https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  39. Java Interview Questions Q16. Can you override a private or static method in Java? https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  40. Java Interview Questions Q16. Can you override a private or static method in Java? A private method cannot be overridden since it is not visible from any other class. If you create a similar method with same return type and same method arguments in child class then it will hide the super class method; this is known as method hiding. ➢ ➢ https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  41. Java Interview Questions Q17. What is multiple inheritance and does java support? https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  42. Java Interview Questions Q17. What is multiple inheritance and does java support? Class A ➢ If a child class inherits the property from multiple classes is known as multiple inheritance. ➢ The problem with multiple inheritance is that if multiple parent classes have a same method name, then at runtime it becomes difficult for the compiler to decide which method to execute from the child class Class A Class A Class A https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  43. Java Interview Questions Q18. What will be the output of this program? https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  44. Java Interview Questions Q18. What will be the output of this program? Output: I am foo in Super I am foo in Child I am bar in Child I am bar in Child https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  45. Java Interview Questions Q19. What will be the output of this program? https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  46. Java Interview Questions Q19. What will be the output of this program? Output: How are you? Hello Hi https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  47. Java Interview Questions Q20. What will be the output of this program? https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  48. Java Interview Questions Q20. What will be the output of this program? Output: First 2 Third 0 Second 2 Fourth 6 6 https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

  49. JDBC OOPS Questions Hibernate Spring Basic Questions Servlets

  50. Java Interview Questions Q21. What is a Servlet? https://www.edureka.co/java-j2ee-soa-training EDUREKA JAVA /J2EE SOA CERTIFICATION TRAINING

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