Lambda Expressions , Interface Default and Static Methods , Method Reference , Parameters Name , Optional , Streams, Concurrency.
Factory is a creational design pattern whereas Strategy is behavioral design pattern. Factory revolves around the creation of object at runtime whereas Strategy or Policy revolves around the decision at runtime.
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.
The best practice guideline between settings.xml and pom.xml is that configurations in settings.xml must be specific to the current user and that pom.xml configurations are specific to the project.
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.
Simplest implementation we can have is a List wherein we can place ordered words and hence can perform Binary Search.
Other implementation with better search performance is to use HashMap with key as first character of the word and value as a LinkedList.
Further level up, we can have linked Hashmaps like ,
a ( key ) -> hashmap (key-aa , value (hashmap(key-aaa,value)
b ( key ) -> hashmap (key-ba , value (hashmap(key-baa,value)
z( key ) -> hashmap (key-za , value (hashmap(key-zaa,value)
upto n levels ( where n is the average size of the word in dictionary.
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.
In first case, there would be 2 DB calls in worst case and 1 in best case. In 2nd approach there will be always 2 DB calls.
Decision on the approach should depend on the following considerations -
@How costly is the call to DB. Are we using indices , hibernate etc
If calls to DB are costly , 1st approach should be the choice.
@Exception Book keeping load upon exception.
The benefit of saving 1st call in approach 1 should be bigger than the Book keeping for the exception.
@Probability of the exception in first apparoach.
If the DB Table is almost empty, it makes sense to follow Approach 1 as majority of the 1st calls will pass through without exception.
The Difference between these patterns in only the intent. Adapter is used because the objects in current form cannot communicate where as in Facade , though the objects can communicate , A Facade object is placed between the client and subject to simplify the interface.
When multiple external resources are trying to access the DB locks and runs into cyclic wait, it may makes the DB unresponsive.
Deadlock can be avoided using variety of measures, Few listed below:
With the advent of Internet, HTTP is the most preferred way of communication. Most of the clients ( web thin client , web thick clients , mobile apps ) are designed to communicate using http only. Web Services using http makes them accessible from vast variety of client applications.
No, Java runs on a virtual machine called JVM and hence doesn't embed well with the underlying hardware. Though we can create a platform independent system software but that would be really slow and that's what we would never need.
Builder is a creational Design Pattern whereas Composite is a structural design pattern. Composite creates Parent - Child relations between your objects while Builder is used to create group of objects of predefined types.
Class , Heap , Stack , Register , Native Method Stack.
Session info in the request can be intercepted and hence a vulnerability. Cookie can be read and write by respective domain only and make sure that right session information is being passed by the client.
Volatile is an instruction that the variables can be accessed by multiple threads and hence shouldn't be cached. As volatile variables are never cached and hence their retrieval cannot be optimized.
Adapter object has a different input than the real subject whereas Proxy object has the same input as the real subject. Proxy object is such that it should be placed as it is in place of the real subject.
Use Case Diagram, Component Diagram for High level Design and Class Diagram , Sequence Diagram for low level design.
Strategy deals only with decision making at runtime so Interfaces should be used.
If its already there in Maven local repository, We can add that as a dependency in the project pom file with its Group Id, Artifact Id and version.
We can provide additional attribute SystemPath if its unable to locate the jar in the local repository.
If its not there in the local repository, we can install it first in the local repository and then can add it as dependency.
We as a team of developers , testers , analyst , lead and architect sit close to each other. Most of the time I would just jump to their seat and talk to them ( if required ). We have daily stand up where we discuss things that needs team attention.
We have multi tier architecture with multiple layers , We have series of web servers and applications in application tier, infrastructure libraries at middle tier and Database servers at the lower tier. We are using Oracle as Database, ESB ( Enterprise service Bus ) for asynchronous communication and Rest Web Services.