Search Interview Questions |  More than 3000 questions in repository. There are more than 900 unanswered questions. Click here and help us by providing the answer. Have a video suggestion. Click Correct / Improve and please let us know. |
|
|||
|
| ||||
| Interview Questions and Answers - Order By Rating | ||||
 | ||||
 Frequently asked in Infosys India | ||||
| ||||
| Ans. String pool (String intern pool) is a special storage area in Java heap. When a string is created and if the string already exists in the pool, the reference of the existing string will be returned, instead of creating a new object and returning its reference. | ||||
| Help us improve. Please let us know the company, where you were asked this question : | ||||
 Discuss Correct / Improve  java oops string string class string pool heap memory  Asked in 31 Companies  intermediate  frequent | ||||
 Try 2 Question(s) Test | ||||
| Advanced level question. Frequently asked in High end product companies. Frequently asked in Google , Cognizant and Deloitte ( Based on 2 feedback ) | ||||
| ||||
| Ans. 1. String Pool - When a string is created and if it exists in the pool, the reference of the existing string will be returned instead of creating a new object. If string is not immutable, changing the string with one reference will lead to the wrong value for the other references. Example - String str1 = "String1"; String str2 = "String1"; // It doesn't create a new String and rather reuses the string literal from pool // Now both str1 and str2 pointing to same string object in pool, changing str1 will change it for str2 too 2. To Cache its Hashcode - If string is not immutable, One can change its hashcode and hence it's not fit to be cached. 3. Security - String is widely used as parameter for many java classes, e.g. network connection, opening files, etc. Making it mutable might possess threats due to interception by the other code segment. | ||||
| Help us improve. Please let us know the company, where you were asked this question : | ||||
| Discuss Correct / Improve java oops string string class immutable immutability advanced Asked in 39 Companies expert frequent | ||||
| Try 4 Question(s) Test | ||||
| Very Frequently asked to fresh graduates and less experienced. Favorite question in Walk in drives. Frequently asked in Indian Services companies. | ||||
| ||||
| Ans. Overloading - Similar Signature but different definition , like function overloading. Overriding - Overriding the Definition of base class in the derived class. | ||||
 Sample Code for overloading Sample Code for overriding | ||||
| Help us improve. Please let us know the company, where you were asked this question : | ||||
| Discuss Correct / Improve java oops overloading overriding oops concepts basic interview question overloading vs overriding Asked in 86 Companies basic frequent | ||||
| Try 1 Question(s) Test | ||||
| ||||
| Ans. Vectors are synchronized whereas Array lists are not. | ||||
| Help us improve. Please let us know the company, where you were asked this question : | ||||
| Discuss Correct / Improve java basic interview question vector arraylist collections synchronization vector vs arraylist Asked in 35 Companies basic frequent | ||||
| Frequently asked question for intermediate developers. Frequently asked in HCL Technologies and EPAM. | ||||
| ||||
| Ans. Volatile is a declaration that a variable can be accessed by multiple threads and hence shouldnt be cached. | ||||
| Sample Code for volatile | ||||
| Help us improve. Please let us know the company, where you were asked this question : | ||||
| Discuss Correct / Improve java oops synchronization volatile java keywords Asked in 42 Companies intermediate frequent | ||||
| Try 1 Question(s) Test | ||||
| Very frequently asked in phone and walk in interviews. | ||||
| ||||
| Ans. An interface without any method declaration is called as marker interface. there are 3 in-built interfaces in JVM i.e. serializable, clonable, remote | ||||
| Help us improve. Please let us know the company, where you were asked this question : | ||||
| Discuss Correct / Improve java oops interfaces marker interface serializable clonable Asked in 21 Companies intermediate frequent | ||||
| Try 1 Question(s) Test | ||||
| Very frequently asked. Favorite question in Walk in Drive of many Indian service companies. Frequently asked in HCL Technologies, TCS and Accenture. | ||||
| ||||
| Ans. final - constant variable, objects cannot be de-referenced, restricting method overriding, restricting class sub classing. finally - handles exception. The finally block is optional and provides a mechanism to clean up regardless of what happens within the try block. Use the finally block to close files or to release other system resources like database connections, statements etc. finalize() - method helps in garbage collection. A method that is invoked before an object is discarded by the garbage collector, allowing it to clean up its state. | ||||
| Sample Code for final Sample Code for finally Sample Code for finalize | ||||
| Help us improve. Please let us know the company, where you were asked this question : | ||||
| Discuss Correct / Improve java oops final finally finalize final vs finally vs finalize Asked in 61 Companies basic frequent | ||||
| Try 4 Question(s) Test | ||||
| ||||
| Ans. Translation of JSP PageCompilation of JSP PageClassloading (class file is loaded by the classloader)Instantiation (Object of the Generated Servlet is created).Initialization ( jspInit() method is invoked by the container).Reqeust processing ( _jspService() method is invoked by the container).Destroy ( jspDestroy() method is invoked by the container). | ||||
| Help us improve. Please let us know the company, where you were asked this question : | ||||
| Discuss Correct / Improve j2ee servlets servelets web application jsp jsp life cycle mindtree Asked in 9 Companies | ||||
| ||||
| Ans. The memory pool containing all the reflective data of the java virtual machine itself, such as class and method objects. With Java VMs that use class data sharing, this generation is divided into read-only and read-write areas. The Permanent generation contains metadata required by the JVM to describe the classes and methods used in the application. The permanent generation is populated by the JVM at runtime based on classes in use by the application. In addition, Java SE library classes and methods may be stored here. | ||||
| Help us improve. Please let us know the company, where you were asked this question : | ||||
| Discuss Correct / Improve java jvm memory management permgen permanent generation advanced architecture Asked in 9 Companies expert | ||||
| ||||
| Ans. Implementation Hiding is a broader concept. Abstraction is a way of implementation hiding in OOP's. | ||||
| Help us improve. Please let us know the company, where you were asked this question : | ||||
| Discuss Correct / Improve java oops oops concepts abstraction hiding information build management | ||||
| Very frequently asked in HCL Tech ( Based of 4 inputs ) | ||||
| ||||
| Ans. Using String method - new StringBuffer(str).reverse().toString(); Iterative - public static String getReverseString(String str){ StringBuffer strBuffer = new StringBuffer(str.length); for(int counter=str.length -1 ; counter>=0;counter--){ strBuffer.append(str.charAt(counter)); } return strBuffer; } Recursive - public static String getReverseString(String str){ if(str.length <= 1){ return str; } return (getReverseString(str.subString(1)) + str.charAt(0); } | ||||
| Help us improve. Please let us know the company, where you were asked this question : | ||||
| Discuss Correct / Improve java string reverse stringbuffer string class code Asked in 6 Companies frequent | ||||
| ||||
| Ans. Encapsulation | ||||
| Help us improve. Please let us know the company, where you were asked this question : | ||||
| Discuss Correct / Improve java java concepts java features oops concepts oops features access protection information hiding | ||||
| Frequently asked in face to face interviews. | ||||
| ||||
| Ans. int count = 15; int[] fibonacci = new int[count]; fibonacci[0] = 0; fibonacci[1] = 1; for(int x=2; x < count; x++){ fibonacci[x] = fibonacci[x-1] + fibonacci[x-2]; } for(int x=0; x< count; x++){ System.out.print(fibonacci[x] + " "); } | ||||
| Help us improve. Please let us know the company, where you were asked this question : | ||||
| Discuss Correct / Improve ebay fibonacci series Asked in 66 Companies basic frequent | ||||
| ||||
| Ans. There are 2 reasons for it. 1. Usage of Primitive types - Though Java provides classes for the primitive data types but as the usage of primitives is permissible, its considered unpure OOP's language. 2. Usage of Static members - Static members belong to the class and not objects and hence not considered fit for pure OOP's programming. | ||||
| Help us improve. Please let us know the company, where you were asked this question : | ||||
| Discuss Correct / Improve oops object oriented programming object oriented language primitive data types Asked in 2 Companies | ||||
| | ||||
When String literals are compared using ==, they always returns true if the string values are same because .. 
