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Q1803. Given a string with multiple opening and closing brackets, determine if the string is valid or not ( to see if the string has all closing brackets for each opening bracket ) ?
Just like Strings, java maintains an integer constant pool too. So 1 will be maintained in integer constant pool and hence reference int2 will point to same integer in pool.
String pool is only for string literals ( defined by "" ) and not for newly created objects and hence str1 == str2 will return false as they are separate objects in memory.
String pool is used for storing string literals so that they can be reused and str3 and str4 will point to same string literal in string pool.
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LikeDiscussCorrect / Improve  string pool  integer constant pool  string comparison  integer comparison
Q1808. Does a Junit without any assertions makes any sense ?
Ans. Yes, If we are testing a code segment to check if throws / doesn't throw an exception. Moreover while testing void methods, we may just verify and not use assert.
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Q1809. 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
Q1810. 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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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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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. 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. 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. 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. 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. 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. 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. 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. It's a facility to shout out your code changes to other collaborators before merging them to the main repository. For example - one may like to have code changes reviewed between his branch and master before merging it to master. So he can open a pull request with the difference between branch and master, get it reviewed and then merge it to master.
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Ans. There are 2 ways to specify dependencies in Spring, one by the way of specifying beans in config files and other is by specifying annotations like @Bean, @Component , @Service etc to let spring know of the dependencies.
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Ans. assertThat is introduced with Junit4 and offers many advatanges over assert. Messages are more explanatory, offer better type safety and are more readable. Moreover hamcrest library is portable as it can used both with junit and TestNG.Moreover assertThat provides flexibility as the same method can be used for assert , assertEquals,assertTrue etc through the use of matcher methods.
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Q1830. 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);