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Which of the following Java feature promotes access protection or Hiding ?
Inheritance
Encapsulation
Abstraction
Composition
Which of the following is true ?
Composition is Tightly Bound
Inheritance is Tightly Bound
Object can only hold reference of only one other object
A Class cannot be extended by multiple classes
Q156. Will the static block be executed in the following code ? Why ?
class Test { static { System.out.println("Why I am not executing "); } public static final int param=20; }
public class Demo { public static void main(String[] args) { System.out.println(Test.param); } }
Ans. No the static block won't get executed as the referenced variable in the Test class is final. Compiler replaces the content of the final variable within Demo.main method and hence actually no reference to Test class is made.
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public static void main(String[] args){
System.out.println("Main Method");
new BuggyBread();
}
}
Instance Initialization Block
Constructor
Static Block
Main Method
Static Block
Instance Initialization Block
Constructor
Main Method
Main Method
Static Block
Instance Initialization Block
Constructor
Static Block
Main Method
Instance Initialization Block
Constructor
Q157. Difference between new operator and Class.forName().newInstance() ?
Ans. new operator is used to statically create an instance of object. newInstance() is used to create an object dynamically ( like if the class name needs to be picked from configuration file ). If you know what class needs to be initialized , new is the optimized way of instantiating Class.
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Ans. 1. It shouldn't result in infinite loop. Please make sure that you have a condition that will terminate the loop and that condition should be reached.
2. Make sure to use the break statement if you aspire to only look for something. Not using break will unnecessarily execute it till the end of for loop in some cases.
3. Similarly use continue to execute the loop with next iteration and bypass the rest of the code block if required.
4. Try to avoid multiple nesting of for loops. If it''s required, Make sure to use break and continue properly so as to avoid some unnecessary processing.
5. Make sure to use try catch within the loop and not outside the for loop if you expect it to continue if one of the iteration fails.
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LikeDiscussCorrect / Improve java loops continue break for loop control statements loop statement.while loop control statements loop statement architecture
Frequently asked to fresh graduates and less experienced developers. Among the first few questions in many interviews.
Q162. What are the difference between composition and inheritance in Java?
Ans. Composition - has-a relationship between objects.
Inheritance - is-a relationship between classes.
Composition - Composing object holds a reference to composed objects and hence relationship is loosely bound.
Inheritance - Derived object carries the base class definition in itself and hence its tightly bound.
Composition - Used in Dependency Injection
Inheritance - Used in Runtime Polymorphism
Composition - Single class objects can be composed within multiple classes.
Inheritance - Single class can only inherit 1 Class.
Composition - Its the relationship between objects.
Inheritance - Its the relationship between classes.
Ans. Derived object carries the body of its class as well as the body of the parent class. Its body ( member elements ) is initialized using its own class constructor whereas the body ( member elements ) carried from the parent class are initialized using super class constructor. So In order to initialize the elements of the parent class before its own elements are even initialized, super is called.
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Q169. Which access specifiers can be used with top level class ? a. public or default b. public or private c. public or protected d. protected or default
Q170. Which of the following can be marked static ?
a. Methods , Variables and Initialization Blocks.
b. Methods , Variables , Initialization Blocks and Outer Classes and nested Classes.
c. Methods , Variables , Initialization Blocks and Outer Classes.
d. Methods , Variables , Initialization Blocks and nested Classes
Methods , Variables , Initialization Blocks and Outer Classes and nested Classes.
Methods , Variables , Initialization Blocks and Outer Classes.
Methods , Variables , Initialization Blocks and nested Classes.
Which of the following cannot be marked static ?
Constructors , Classes ( Outer ) , Classes ( nested ), Interfaces , Local variables , Inner Class methods and instance variables.
Constructors , Classes ( Outer ) , Interfaces , Local variables , Class variables , Class Methods , Inner Class methods and instance variables.
Constructors , Classes ( Outer ) , Interfaces , Local variables , Inner Class methods and instance variables.
Constructors , Classes ( Outer ) , Classes (Nested), Interfaces , Local variables , Inner Class methods and instance variables.
Q171. Which of the following cannot be marked static ?
a. Constructors , Classes ( Outer ) , Classes ( nested ), Interfaces , Local variables , Inner Class methods and instance variables. b. Constructors , Classes ( Outer ) , Interfaces , Local variables , Class variables , Class Methods , Inner Class methods and instance variables. c. Constructors , Classes ( Outer ) , Interfaces , Local variables , Inner Class methods and instance variables. d. Constructors , Classes ( Outer ) , Classes (Nested), Interfaces , Local variables , Inner Class methods and instance variables
Ans. Constructors , Classes ( Outer ) , Interfaces , Local variables , Inner Class methods and instance variables.
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Methods , Variables , Initialization Blocks and Outer Classes and nested Classes.
Methods , Variables , Initialization Blocks and Outer Classes.
Methods , Variables , Initialization Blocks and nested Classes.
Which of the following cannot be marked static ?
Constructors , Classes ( Outer ) , Classes ( nested ), Interfaces , Local variables , Inner Class methods and instance variables.
Constructors , Classes ( Outer ) , Interfaces , Local variables , Class variables , Class Methods , Inner Class methods and instance variables.
Constructors , Classes ( Outer ) , Interfaces , Local variables , Inner Class methods and instance variables.
Constructors , Classes ( Outer ) , Classes (Nested), Interfaces , Local variables , Inner Class methods and instance variables.
Q172. Interface can only have ...
a. Member elements and Methods. b. Static Variables and Static Methods. c. Static Final Variables and Instance Method Declarations. d. Member Elements , Instance Methods, Static variables and Static Methods.
Ans. Static Final Variables and Instance Method Declarations.
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Q173. Which of the following is not the difference between Singleton and Static class ( Class with static members only ) ?
a. Only one object can be created for Singleton class whereas No objects are created for static class. b. Singleton class instance is initiated using new keyword whereas static class instance is created using static method. c. Singleton class can be serialized whereas Static class cannot be. d. Singleton Class can participate in runtime Polymorphism whereas Static class cannot.
Ans. Singleton class instance is initiated using new keyword whereas static class instance is created using static method.
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Q174. Which of the following is false about Constructors ?
a. Constructor can be overloaded b. A no argument constructor is provided by the compiler if we declare only constructors with arguments. c. Constructors shouldn't have any return types , not even void. d. If super is not explicitly called, still super() is intrinsically added by the compiler.
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Which of the following Java feature promotes access protection or Hiding ?
