1600 PMP mock questions 1400 CAPM mock questions 800 SCJP 6 mock questions 600 OCAJP 7 mock questions 590 OCPJP 7 mock questions 556 SCWCD 5 mock questions 500 OCEJWCD 6 mock questions pdfDownload (java,struts, hibernet etc)

OOPs and Design Pattern interview questions

  • What is Observer pattern ? Explain with Code Example ? view answer
  • "is-a" relationship describes inheritance relationship between objects view answer
  • has-a relationship, which is also called object composition view answer
  • The four main concepts are involved in OOP view answer
  • Example Java Code For Association & Aggregation & Composition view answer
  • What are the common things need to consider while Creating and Destroying Objects view answer
  • what is the difference between encapsulation and data hiding? explain with Code example? view answer
  • Dependency In Java view answer
  • Is Singleton class is serialized ? view answer
  • What is Singleton ? and Double-checked locking ? view answer
  • What is Factory Method pattern? view answer
  • What is Adapter pattern ? view answer
  • What is Proxy and Decorator patterns ? With Java Example ? view answer
  • Brief Introduction to OOP Concepts view answer
  • What is Abstract Factory Pattern ? With Code Example ? view answer

!!! OOPs and Design Pattern interview questions !!!

What is Adapter pattern ?

The Adapter pattern is typically used to allow the reuse of a class that is similar, but not the
same, as the class the client class would like to see. Typically the original class is capable of
supporting the behavior the client class needs, but does not have the interface the client
class expects, and it is not possible or practical to alter the original class. Perhaps the source
code is not available, or it is used elsewhere and changing the interface is inappropriate.
Here is an example that wraps OldClass so a client class can call it using a method,
NewMethod() defined in NewInterface:
public class OldClassAdapter implements NewInterface {
private OldClass ref;
public OldClassAdapter(OldClass oc)
ref = oc;
public void NewMethod()

Example :

interface Contact{
    public String getLastName();

//adapter class to connect old interface and get the value
class ContactAdapter implements Contact{
    private DataBaseContactInf contact;
    public ContactAdapter()
        contact = new DataBaseContactImpl();
        public String getLastName(){
            return contact.getLName();

    //old interface and classs
interface DataBaseContactInf {
    public String getLName();
class DataBaseContactImpl implements DataBaseContactInf {
    public String getLName() {
        return "das";

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