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Ans. Yes but as Hibernate creates the Proxy Classes inherited from the Entity Classes to communicate with Database for lazy initialization. Declaring entity classes as final will prohibit communication with database lazily and hence will be a performance hit.
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Q2254. What are the annotations used in Junit with Junit4 ?
Ans. @Test
The Test annotation indicates that the public void method to which it is attached can be run as a test case.
@Before
The Before annotation indicates that this method must be executed before each test in the class, so as to execute some preconditions necessary for the test.
@BeforeClass
The BeforeClass annotation indicates that the static method to which is attached must be executed once and before all tests in the class.
@After
The After annotation indicates that this method gets executed after execution of each test.
@AfterClass
The AfterClass annotation can be used when a method needs to be executed after executing all the tests in a JUnit Test Case class so as to clean-up the set-up.
@Ignores
The Ignore annotation can be used when you want temporarily disable the execution of a specific test.
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Ans. With Java 8, We can provide method definitions in the Interfaces that gets carried down the classes implementing that interface in case they are not overridden by the Class. Keyword "default" is used to mark the default method.
Q2262. Can a class implement two Interfaces having default method with same name and signature ?
public interface DefaultMethodInterface { default public void defaultMethod(){ System.out.println("DefaultMethodInterface"); } }
public interface DefaultMethodInterface2 { default public void defaultMethod(){ System.out.println("DefaultMethodInterface2"); } }
public class HelloJava8 implements DefaultMethodInterface,DefaultMethodInterface2 { public static void main(String[] args){ DefaultMethodInterface defMethIn = new HelloJava8(); defMethIn.defaultMethod(); } }
Ans. No. Compiler gives error saying "Duplicate Default Methods"
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Q2263. What If we make the method as abstract in another Interface ?
public interface DefaultMethodInterface { default public void defaultMethod(){ System.out.println("DefaultMethodInterface"); } }
public interface DefaultMethodInterface2 { public void defaultMethod(){ System.out.println("DefaultMethodInterface2"); } }
public class HelloJava8 implements DefaultMethodInterface,DefaultMethodInterface2 { public static void main(String[] args){ DefaultMethodInterface defMethIn = new HelloJava8(); defMethIn.defaultMethod(); } }
Ans. Even then the Compiler will give error saying that there is a conflict.
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Q2264. What if we override the conflicting method in the Class ?
public interface DefaultMethodInterface { default public void defaultMethod(){ System.out.println("DefaultMethodInterface"); } }
public interface DefaultMethodInterface2 { default public void defaultMethod(){ System.out.println("DefaultMethodInterface2"); } }
public class HelloJava8 implements DefaultMethodInterface,DefaultMethodInterface2 { public static void main(String[] args){ DefaultMethodInterface defMethIn = new HelloJava8(); defMethIn.defaultMethod(); }
public void defaultMethod(){ System.out.println("HelloJava8"); } }
Ans. There won't be any error and upon execution the overriding class method will be executed.
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Q2265. What will happen if there is a default method conflict as mentioned above and we have specified the same signature method in the base class instead of overriding in the existing class ?
Ans. There won't be any problem as the Base class method will have precedence over the Interface Default methods.
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Q2266. If a method definition has been specified in Class , its Base Class , and the interface which the class is implementing, Which definition will be picked if we try to access it using Interface Reference and Class object ?
Ans. Class method definition is overriding both the definitions and hence will be picked.
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Q2267. If a method definition has been specified in the Base Class and the interface which the class is implementing, Which definition will be picked if we try to access it using Interface Reference and Class object ?
Ans. Base Class Definition will have precedence over the Interface Default method definition.
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Q2270. Can we have default method with same name and signature in the derived Interface as the static method in base Interface and vice versa ?
Ans. Yes , we can do that as static methods are not accessible using references and hence cannot lead to conflict. We cannot do inverse as Default methods cannot be overridden with the static methods in derived interface.
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Q2277. What things you would care about to improve the performance of Application if its identified that its DB communication that needs to be improved ?
Very frequently asked. Usually followed by questions related to private constructor and synchronized access. Frequently asked in JPMorgan and TCS (Based on 2 feedback)
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Which Java version introduced Lambda expressions ?
