Core Java - Interview Questions and Answers for 'Memory' | Search Interview Question

Interview Questions and Answers - Order By Rating

Q31. What is a class loader ? What are the different class loaders used by JVM ?

Ans. Part of JVM which is used to load classes and interfaces.

Bootstrap , Extension and System are the class loaders used by JVM.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java class loaders classloaders jvm java memory management advanced Asked in 3 Companies}

Q32. Explain java.lang.OutOfMemoryError ?

Core Java

Ans. This Error is thrown when the Java Virtual Machine cannot allocate an object because it is out of memory, and no more memory could be made available by the garbage collector.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java exceptions jvm outofmemoryerror Asked in 1 Companies}

Q33. Should we override finalize method ?

Ans. Finalize is used by Java for Garbage collection. It should not be done as we should leave the Garbage Collection to Java itself.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java garbage collection java memory management finalize}

Try 2 Question(s) Test

Q34. Which kind of memory is used for storing object member variables and function local variables ?

Ans. Local variables are stored in stack whereas object variables are stored in heap.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java jvm memory management stack memory heap memory expert}

Q35. Why do member variables have default values whereas local variables don't have any default value ?

Core Java

Ans. member variable are loaded into heap, so they are initialized with default values when an instance of a class is created. In case of local variables, they are stored in stack until they are being used.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java jvm memory management variables stack memory heap memory default values expert}

Q36. Why Java don't use pointers ?

Ans. Pointers are vulnerable and slight carelessness in their use may result in memory problems and hence Java intrinsically manage their use.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java jvm memory management pointers intermediate}

Advanced level question. Recently asked in few Indian service companies ( Based on 3 inputs )

Q37. What are various types of Class loaders used by JVM ?

Core Java

Ans. Bootstrap - Loads JDK internal classes, java.* packages.

Extensions - Loads jar files from JDK extensions directory - usually lib/ext directory of the JRE

System - Loads classes from system classpath.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java jvm memory management class loaders bootstrap extensions system classloaders advanced technical lead technical architect Asked in 7 Companies}

Q38. How are classes loaded by JVM ?

Core Java

Ans. Class loaders are hierarchical. The very first class is specially loaded with the help of static main() method declared in your class. All the subsequently loaded classes are loaded by the classes, which are already loaded and running.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java jvm memory management class loaders classloaders Asked in 1 Companies}

Q39. Difference between static vs. dynamic class loading?

Core Java

Ans. static loading - Classes are statically loaded with Java new operator.

dynamic class loading - Dynamic loading is a technique for programmatically invoking the functions of a class loader at run time.

Class.forName (Test className);

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java jvm memory management class loaders classloaders static class loading static loading dynamic class loading dynamic loading Asked in 2 Companies expert frequent}

Q40. What are strong, soft, weak and phantom references in Java ?

Core Java

Ans. Garbage Collector wont remove a strong reference.

A soft reference will only get removed if memory is low.

A weak reference will get removed on the next garbage collection cycle.

A phantom reference will be finalized but the memory will not be reclaimed. Can be useful when you want to be notified that an object is about to be collected.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java memory management jvm garbage collections references strong reference soft reference weak reference phantom reference architecture Asked in 2 Companies}

Q41. Name few tools for probing Java Memory Leaks ?

Ans. JProbe, OptimizeIt

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java tools jvm memory management memory leaks jprobe optimeit architecture technical lead}

Q42. Which memory areas does instance and static variables use ?

Core Java

Ans. instance variables and objects are stored on heap and the references are stored on stack whereas static variables are stored in the method area of heap.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java jvm memory management memory heap stack}

Try 2 Question(s) Test

Q43. What is PermGen or Permanent Generation ?

Core Java

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 :

_{Like Discuss Correct / Improve java jvm memory management permgen permanent generation advanced architecture Asked in 9 Companies expert}

Q44. What is metaspace ?

Core Java

Ans. The Permanent Generation (PermGen) space has completely been removed and is kind of replaced by a new space called Metaspace. The consequences of the PermGen removal is that obviously the PermSize and MaxPermSize JVM arguments are ignored and you will never get a java.lang.OutOfMemoryError: PermGen error.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java jvm memory management permgen permanent generation metaspace advanced architecture expert}

Q45. What are the disadvantages of using arrays ?

Core Java

Ans. Arrays are of fixed size and have to reserve memory prior to use. Hence if we don't know size in advance arrays are not recommended to use.

Arrays can store only homogeneous elements.

Arrays store its values in contentious memory location. Not suitable if the content is too large and needs to be distributed in memory.

There is no underlying data structure for arrays and no ready made method support for arrays, for every requriment we need to code explicitly

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java arrays disadvantages of arrays arrays memory arrays vs variables}

Q46. Can we call the garbage collector explicitly ?

Core Java

Ans. Yes, We can call garbage collector directly but it doesn't guarantees that the gc will start executing immediately. This gc( ) method appears in both Runtime and System classes of java.lang package.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java garbage collection java memory management jvm gc yes no Asked in 4 Companies expert}

Try 1 Question(s) Test

Q47. What are different ways to create String Object? Explain.

Core Java

Ans. There are total six ways

1. literals

When we create a String using double quotes, JVM looks in the String pool to find if any other String is stored with same value. If found, it just returns the reference to that String object else it creates a new String object with given value and stores it in the String pool.

2. new keyword

When we use new operator, JVM creates the String object but dont store it into the String Pool. We can use intern() method to store the String object into String pool or return the reference if there is already a String with equal value present in the pool.

3. string buffer
4. string builder
5. System.out.println
6. char to string

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java string class string jvm memory management string pool Asked in 5 Companies basic frequent}

Try 3 Question(s) Test

Q48. How substring() method of String class create memory leaks?

Core Java

Ans. substring method would build a new String object keeping a reference to the whole char array, to avoid copying it. Hence you can inadvertently keep a reference to a very big character array with just a one character string.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java string class string substring memory leaks jvm memory management advanced architecture technical architect technical lead expert}

Q49. Name few classes java provides for memory management ?

Ans. http://www.buggybread.com/2015/01/java-memory-classes-and-interfaces.html

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java memory management}

Q50. Difference between Stack and Heap memory ?

Core Java

Ans. Stack memory areas is used to hold method and local variables while objects are always allocated memory in the heap. The heap memory is shared between multiple threads whereas Stack memory isn't.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java memory management stack memory heap memory difference between ebay Asked in 2 Companies intermediate frequent}

Try 1 Question(s) Test

Q51. What is OutOfMemoryError in Java?

Core Java

Ans. OutOfMemoryError in Java is a subclass of VirtualMachineError and is thrown by JVM when it runs out of heap memory.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve outofmemoryerror error exceptions jvm java heap memory heap}

Q52. What will happen if we don't have termination statement in recursion ?

Ans. Function call allocates a stackframe in stack. Every stackframe will use some memory to store local variables, parameters and to remember return address. Without terminating condition stackframes will keep consuming memory from stack and eventually program will result in stackoverflow error.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve recursion break statement break stackoverflow exception stackoverflow memory management memory exceptions}

Q53. Function variables are kept in ..

Core Java

a. Stack

b. Heap

c. Both Stack and Heap

d. None of them

Ans.a. Stack

Q54. Which memory segment holds String Pool ?

Core Java

a. Stack

b. Heap

c. Code Segment

d. Class Segment

Ans.b. Heap

Q55. In this code

public class BuggyBread1{
   private static String staticVariable = "static Variable";

   private String instanceVariable = "instance Variable";

   public static void main (String args[]) {
String localVariable = "local Variable";
}
}

Where will the value 'static Variable' be stored ?

Core Java

a. Stack Memory Segment

b. Heap Memory Segment

c. Runtime Constant Pool within Heap Segment

d. Code Segment

Ans.c. Runtime Constant Pool within Heap Segment

Q56. In this code

public class BuggyBread1{
   private static String staticVariable = "static Variable";

   private String instanceVariable = "instance Variable";

   public static void main (String args[]) {
String localVariable = "local Variable";
}
}

Where will the value 'static Variable' be stored ?

Core Java

a. Stack Memory Segment

b. Heap Memory Segment

c. Runtime Constant Pool within Heap Segment

d. Code Segment

Ans.c. Runtime Constant Pool within Heap Segment

Q57. In this code

public class BuggyBread1{
   private static String staticVariable = "static Variable";

   private String instanceVariable = "instance Variable";

   public static void main (String args[]) {
String localVariable = new String("local Variable");
}
}

Where will the value 'local Variable' be stored ?

Core Java

a. Stack Memory Segment

b. Heap Memory Segment

c. Runtime Constant Pool within Heap Segment

d. Code Segment

Ans.a. Stack Memory Segment

Q58. In this code

public class BuggyBread1{
   private static String staticVariable = new String("static Variable");

   private String instanceVariable = "instance Variable";

   public static void main (String args[]) {
String localVariable = "local Variable";
}
}

Where will the value 'static Variable' be stored ?

Core Java

a. Stack Memory Segment

b. Heap Memory Segment

c. Runtime Constant Pool within Heap Segment

d. Code Segment

Ans.b. Heap Memory Segment

Q59. Which of following memory segment is cleaned by Garbage Collection Mechanism ?

Core Java

a. Stack

b. Heap

c. Code

d. Cache

Ans.b. Heap

Search Interview Questions

Help us and Others Improve. Please let us know the questions asked in any of your previous interview.