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Q1061. What will happen if we have our own constructor but only initialize some of the member elements ?
Ans. Its always advisable to initialize all the member elements in case we don't use the compiler's default constructor as leftover member elements will have garbage values and may reflect and unstable state for the object.
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Ans. JRE or Java Runtime Environment is the Java Virtual Machine on which class files are executed. It includes borwser plugins that facilitates execution of class files in browsers.
JDK or Java Development Kit includes JRE , compiler and development tools.
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Q1064. Does Constructor returns the reference of the newly created object ?
Ans. No, New operator actually returns the reference of newly created object. Constructor's purpose is to initialize the default state of the object by setting the initial values of the elements and hence returns nothing.
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Q1065. Why doesn't Java even allow void return types for Constructors ?
Ans. Because having a void return type with the Constructor name will make it as a method name. As methods with the Class names are perfectly legit in Java, It needs some way to recognize the constructor and having none return type helps identify that.
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Ans. Web Service promotes looser coupling but with comes with coding and performance overheads. Jars provide better performance and may be lesser coding but are problematic with update distribution. If the situation doesn't require frequent dependency updates and if it's only read operation of persistence, Having dependencies should be a better choice , otherwise web service.
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Ans. DTO is Data Transfer Object i.e Pojo which is supposed to move between different layers of software architecture for transferring information. Example could be the object passed from client in case of web service call or the object passed to Persister for Database Persistence.
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Ans. DAO is Data Access Object which is used within Persistence Layer to make Database Transaction. For example , the class holding the Database connection and CRUD methods.
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Ans. POJO is Plain Java Object that holds only Member Elements , getters are setters and minimal processing on that. The primary purpose of such object is to either transfer information or keeping state for a while. They are not intended to provide any processing or transformation.
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Ans. Request Body in case of Get Request has no meaning and hence it's not parsed when the request is received. Alternatively Request Parameters are passed as either Path Params or Query Params.
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Ans. We creates separate branches for each project if development work is going on parallel and they are to be released at different times. Once the first release is done, we merge the branch changes into trunk. If they all have to go at one time, we usually would merge everything in the trunk itself.
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Q1079. Is it advisable to just hold checking in your changes to trunk if there is another release planned in between ?
Ans. If it's just smaller change, and single person is working, then this approach is fine. Otherwise there are risk on loosing it on your machine. Moreover , If there are multiple people working , it makes it hard to share code. It's better to create a separate branch and then merge it later to trunk.
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Q1081. If you are supposed to deprecate the method , Will you deprecate the method in the implementation class or will you deprecate the abstract declaration within interface or abstract class ?
Ans. Deprecating the interface / or declaration doesn't make much sense as the implementation is deprecated and not the interface.
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Ans. Multi Level Inheritance is multi level hierarchy of classes. Here is the example - http://www.buggybread.com/2015/09/java-se-class-diagram-classes-that_603.html
Class RoleList extends ArrayList which in turn extends AbstractList which in turn extends AbstractCollection.
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if classes B and C extends Class A, Which of the following initialization is correct ?
B b = new C();
C c = new B();
B b = new A();
A a = new B();
Q1083. When do we generally get the database error - Unique Constraint Violated ?
Ans. This error can result either on an insert, update or delete when any change in data results in duplicate record or subset of it having unique constraint on record or its subset. For example - If we have a unique constraint on a combination of columns and then trying to insert duplicate column values.
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Ans. Audit Tables generally stores Raw information to be reviewed in case of problems or determining impact. If Database space is an issue , and the audit information is rarely retrieved, one design could be to use compressed file system.
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Ans. When a DML is executed, the changes only stays in session and still not pushed to DB Tables, Commit is used to push those changes to the Tables.
In case we realize that we don't want to commit those changes and would like to ignore them, we can use rollback.
For example - You may like that for a banking transaction you would like to update the account balance only if the debit or credit record was correctly inserted, so you may like to encapsulate both DML's - insert for transaction and update for balance in a single transaction and would only commit if both succeeds else rollback.
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Q1087. Can I run a java program without creating any class ?
Ans. No, It requires creation of atleast one Class. Creating an object of that class is not compulsory as we can write all our logic within main method which is static.
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Q1088. What is the difference between print() and println() in Java ?
Ans. print method prints the argument passed to the method whereas println prints the argument and then prints the new line character. println is generally used if we want each output in a new line.
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