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Ans. Asynchronous Replication of information from master to all slaves. Redis is an in memory storage and hence any crash may result in complete loss of information on a cluster.
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Ans. Now the reference points to a new object in memory. If that was the only reference for the previous object , it will be marked for garbage collection.
Foe example -
Object obj = new Object();
obj = new Object();
object created in first line will be eligible for garbage collection after line 2 as it looses all it's handlers.
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Ans. Yes, doesn't provide exclusive access as we cannot allocate and deallocate memory exclusively as Java internally manages it. The advantage of this is that it relieves the coder for such tasks and helps protect from many bugs that may get introduced with imperfect coding. Moreover as java garbage collector collects all unclaimed memory or objects, it helps the application from memory leaks.
On the flip side , as coder doesn't have extensive excess to memory , it is upto java to decide on the state for programming construct and data storage and hence may introduce some security risks. For example - Java keeps string literals in string pool and there is no exclusive way to remove it and hence may stay and sensitive data in string pool may introduce security issues. Moreover when we overwrite a value or object for a variable / reference, it is upto java to purge those values and hence it may stay in memory for a while till java decide that it is no longer referenced and hence should be removed and hence makes it vulnerable for inappropriate access.
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LikeDiscussCorrect / Improve  disadvantages of garbage collection  advantages and disadvantages of java memory management  java for security applications  java with sensitive data  memory management
Q1388. What is event handling ? What is event propagation ?
Q1390. Which of following is / are valid static final declaration ?
public static final String MAX_NUM = "10";
public static final Object NULL = null;
public static final MathContext MATH_CONTEXT = new MathContext(2,RoundingMode.CEILING);
Ans. These are the platforms or set of services provided by Amazon for cloud services , database storage , content delivery and other business applications and solutions.
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Ans. Object is an entity in Java , i.e which has a state ( instance variables ) and methods attached to it ( static or non static , through class definition ). References are the identifiers that are used to point to objects.
For example -
Employee emp = new Employee();
emp = new Employee();
In this code, emp is the reference that gets assigned to the new object created by the new operator. In the second line , we have assigned the same reference to another object. So with these 2 lines of code, we have 2 objects in memory with reference emp now pointing to second object.
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Ans. No, first method is a constructor whereas the second method is just a normal method. There is no way a constructor can be called explicitly and hence all explicit calls to BuggyBread() would result in compilation error.
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Ans. BuggyBread method without any return type is the constructor which get's called upon object creation whereas BuggyBread method with return type of void is just another method that needs to be called explicitly for it's invocation.
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Ans. All methods are not expected to return something but Yes, all methods are expected to have a return type. If a method returns nothing, it can be declared with the return type void.
Constructors are not expected to have any return types , not even void.
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Ans. void is a return type which indicates that the method returns nothing but returns the control to the line next to the method call. All methods need to have a return type and hence a method returning nothing needs to be declared void.
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Ans. equals is the method of Object class that is overridden by the classes to specify object equality criteria.
As every class extends Object class, the default implementation of equals is carried to them. Default implementation specified in the Object class is that two objects are treated equal if they are same.
i.e
Object x = new Object();
Object y = new Object();
x.equals(y); // false
x=y;
x.equals(y); // true
i.e x.equals(y) if only x==y
Now every class has the option to specify their object equality by overriding equals method. For example - String class has implemented in a manner if the string value contained in them is exactly same.
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Ans. String Pool makes Java more memory efficient by providing a reusable place for string literals. It might be a little performance inconvenience but results in good amount memory saving.
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Ans. Both will produce the same output but 1st will consume more resources in terms of memory ( for maintaining intermediate value ) and computing power ( as single mathematical calculation with more operands is more effective than multiple calculations with broken down operands )
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Ans. Eclipse Vert.x is a tool kit for building reactive applications on the JVM. Vert.x is event driven and non blocking. This means the application can handle lot of concurrency using a small number of kernel threads. Vert.x lets the application scale with minimal hardware.
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Ans. Objective of constant variable is to provide a context to the value and provide a single point of change. In terms of context, i don't see much need for having constant name for null as null is already self explanatory. In terms of providing single point of change, it doesn't make much sense as it would necessitate that all such placeholders either hold null or a common value.
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Q1409. If we have to maintain a value "31" denoting "number of days in a month" as constant variable, Which of the following is the best constant name and Why ?
Constant should be such that it uniquely identifies the value it holds and context of the value. THIRTY_ONE uniquely identifies the value but doesn't express the context. NUMBER_OF_DAYS_IN_MONTH expresses the context but doesn't specify the value clearly as different month can have different number of days.
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Q1410. If we have to maintain a value "7" denoting "number of days in a week" as constant variable, Which of the following is the best constant name and Why ?
Constant should be such that it uniquely identifies the value it holds and context of the value. SEVEN uniquely identifies the value but doesn't express the context.
Though NUMBER_OF_DAYS_IN_WEEK and NUMBER_OF_DAYS_IN_WEEK_7 makes sense in terms of unique value identification and context but 7 at the end of constant name appears useless as all weeks have 7 days and hence it's the only value it can hold. If it would have been "number of days in a month", it would have made sense to include number of days at the end like