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Ans. Step 1 - We can create a Registry Class having Map of all created objects as key and References list as value.
Step 2 - Whenever we create an object , we should update the Registry in the constructor to add the new object.
Step 3 - Whenever we assign a new reference to the object , we need to update the entry in Map. Similarly if the reference get's removed ( end of scope etc ), we need to remove the entry of reference from the list.
Step 4 - We can have threaded code to monitor the Map to see if any object looses all it's references and should call the method to destroy object and clean the memory.
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Ans. Initialize an ArrayList that will hold LinkedLists i.e every element of the arraylist will be a linked list.
Such collection could be used in algorithms that require first random access and then sequential traversal. For example - Storing traversal paths for a graph wherein we can start from any vertex. Implementing dictionary with each arraylist element holding staring with character and then linked list holding duplicate words.
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Ans. LocalDate today = LocalDate.now();
LocalDate birthday = LocalDate.of(1960, Month.JANUARY, 1);
Period p = Period.between(birthday, today); //Now access the values as below
System.out.println(period.getDays());
System.out.println(period.getMonths());
System.out.println(period.getYears());
Ans. Yes , a gc method to explicitly call garbage collection immediately on the object. It will provide better flexibility over application that require optimal usage of memory.
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Ans. 1. In Setter Injection, partial injection of dependencies can possible, means if we have 3 dependencies like int, string, long, then its not necessary to inject all values if we use setter injection. If you are not inject it will takes default values for those primitives1. In constructor injection, partial injection of dependencies cannot possible, because for calling constructor we must pass all the arguments right, if not so we may get error
2. Setter Injection will overrides the constructor injection value, provided if we write setter and constructor injection for the same property [i already told regarding this, hope you remember ] But, constructor injection cannot overrides the setter injected values
3. If we have more dependencies for example 15 to 20 are there in our bean class then, in this case setter injection is not recommended as we need to write almost 20 setters right, bean length will increase. In this case, Constructor injection is highly recommended, as we can inject all the dependencies with in 3 to 4 lines [i mean, by calling one constructor]
4. Setter injection makes bean class object as mutable [We can change ] .Constructor injection makes bean class object as immutable [We cannot change ]
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Ans. Sometimes the calls move across layers of classes and functions and hence each layer needs to perform some function like cleaning if something goes wrong deep inside.
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Ans. Manual scaling is the process of scaling instances up and down in a an enviornment manually by observing the scaling trigger whereas Auto scaling is the process wherein a Trigger condition specified as a scaling trigger will trigger scaling up and down of instances.
for example - If an organization has a policy of scaling up if requests / sec / instance exceeds 10000, Operations team will have to manually monitor the metric and they can request scaling up and down as the need arise. Manual scaling offers flexibility as team can scale on the basis of combination of factors and can take decision on flyby requires continuous monitoring.
The same trigger can be fed as triggering policy to the environment and can be taken care by the system. This requires availability of such triggering policy within the environment configuration but as it's automatically handled, requires no supervision.
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Ans. It's a configuration for auto scaling environment that specify the attributes / conditions for scaling instances up and down. For example - We may like environment to scale up when the number of requests / sec increases a particular threshold and scale down when it decreases below a threshold.
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Ans. OOPs or Object Oriented Programming is a Programming model which is organized around Objects instead of processes. Instead of a process calling series of processes, this model stresses on communication between objects. Objects that all self sustained, provide security by encapsulating it's members and providing abstracted interfaces over the functions it performs. OOP's facilitate the following features
1. Inheritance for Code Reuse
2. Abstraction for modularity, maintenance and agility
3. Encapsulation for security and protection
4. Polymorphism for flexibility and interfacing
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Ans. Encapsulation is a feature of OOP's that binds the data and it's associated methods together as a single unit and facilitate protection and data hiding by providing minimal interface to outside. For example - member variables are declared private and are accessed through public methods. Moreover we have private methods that can only be used internally and hence providing minimal interface to outside class through use of public methods.
Ans. We can copy the elements to a Set and then find the difference of count between ArrayList and Set. As Set don't allow duplicates , they will be removed in the set.
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Ans. ArrayLists aren't synchronized and hence doesn't allow synchronized access. As multiple threads can access an arraylist in parallel, it may result in an inconsistent state.
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Ans. It means that only 1 thread can access have access to Vector at a time and no parallel access is allowed whereas Array List allows parallel access by multiple threads.
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Ans. Java Programs are collection of objects that communicates with each other to get a task accomplished. To add to those objects, there are common spaces ( static i.e common for objects belonging to a class ) that are used too.
We can visualize objects as departments of an organization in real world. Just like Task gets initiated in one department and then files are moved across different departments to get work done. In a similar fashion, a task is initiated in one object ( having main method ) and then information ( through POJOs / DTOs ) is moved across objects to accomplish a task.
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