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 223 test questions in repository.




Java - Test Questions on 'Object' - 25 questions found


Which of the following do you think is the primary reason you would never use a static class even the application doesn't need multiple requests or threads ?Core Java
Serialization
Runtime Polymorphism
Lazy Loading
Memory

  static class  static vs singleton  java  oops  objects

What will be the output of following ?

String str1 = new String("String1");
String str2 = new String("String1");
System.out.print(str1 == str2);
System.out.print(str1.equals(str2));
str1 = str2;
System.out.print(str1 == str2);
Core Java
falsetruetrue
truetruetrue
truetruefalse
falsetruefalse

  equals  object equality

What will be the output of following code ?

String str1 = "String1";
String str2 = "String1";
System.out.print(str1 == str2);
System.out.print(str1.equals(str2));
str1 = str2;
System.out.print(str1 == str2);
Core Java
falsetruetrue
falsefalsetrue
truetruetrue
falsefalsefalse

  equals  object equality  string pool

Which of following is not the method of object class ?Core Java
run
notify
wait
clone

  object class

Which of the following is not the use of this keyword ?Core Java
Passing itself to another method
To call the static method
Referring to the instance variable when local variable has the same name
Calling another constructor in constructor chaining

  this  this keyword  java

Which of the following Java feature promotes access protection or Hiding ?Core Java
Inheritance
Encapsulation
Abstraction
Composition

  java  java concepts  java features  oops concepts  oops features  access protection  information hiding

Which of the following statement is not true ?Core Java
x==y means they are pointing to the same object
x==y means that they hold same information
x.equals(y) means they are pointing to the same object
x.equals(y) means that they hold same information

  

When String literals are compared using ==, they always returns true if the string values are same because .. Core Java
of overridden compareTo method
of overridden compare method
of String Pool
== means that the object contents are equal

  

Which of the following Java feature promotes Code Re usability ?Core Java
Abstraction
Encapsulation
Inheritance
Polymorphism

  java  java concepts  java features  code reusability

Which of the following is true ?Core Java
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

  

Overridden methods must have the same ... Core Java
name
name and argument list
name, argument list, and return type
name, argument list, return type and belong to the same class

  java  overriding

Which of the following is not type of inner classes ?Core Java
Simple Inner Class
Static Nested Inner Class
Method Nested Static Inner Class
Anonymous Inner Class

  java  classes  inner classes  nested classes

What is a default constructor ?Core Java
Constructor without parameters declared by user
Constructor provided by Java if no constructor is declared
Constructor with empty body
All of the above

  Constructor

What will be the output of following code ?

String str1 = "String1";
String str2 = "String2";
str1.concat("String3");
System.out.print(str1);
System.out.print(str2);
Core Java
String1String2
String1String3String3
String1String3String1String3
String1String1

  

What will be the output of following code ?

String str1 = "String1";
String str2 = "String2";
str1=str1.concat("String3");
System.out.print(str1);
System.out.print(str2);
Core Java
String1String2
String1String3String2
String1String2String3
String1Stringg3String1

  

Which of the following can be overridden ?Core Java
final instance methods
final static methods
non final instance methods
non final static methods

  overriding

if classes B and C extends Class A, Which of the following initialization is correct ?Core Java
B b = new C();
C c = new B();
B b = new A();
A a = new B();

  inheritance

What will be the output of following code ?

public class BuggyBread {

   private int x;

   private BuggyBread(int x){
      x = x;
   };

   public static void main(String[] args){
      BuggyBread buggybread = new BuggyBread(5);
      System.out.println(buggybread.x);
   }
}
Core Java
compilation error
undefined
0
5

  this keyword  coding  code

What is the relationship between Vehicle and Engine in this example ?

public class Vehicle {
   Enginer engine;
   public void move(){
      engine = new Engine();
      engine.start();
   }
}
Core Java
Composition ( Vehicle has a Engine )
Composition ( Engine has a Vehicle )
Inheritance ( Vehicle is a Engine )
Inheritance ( Engine is a Vehicle )

  composition  inheritance  oops concepts

What is the relationship between Car and Vehicle in the following code ?

public class Car extends Vehicle{
   Engine engine;   
   
   public static void main(String[] args){
      Vehicle vehicle = new Car();
      car.move();
   }   

   public void move(){
      engine = new Engine();
      engine.start();
   }
}
Core Java
Composition ( Vehicle has a Car )
Composition ( Car has a Vehicle )
Inheritance ( Vehicle is a Car )
Inheritance ( Car is a Vehicle )

  Inheritance  Composition  Oops concepts

What is the problem with the following code ?

public class Car extends Vehicle{
   Vehicle vehicle;
   
   Car(){
      super();
      this.vehicle = new Vehicle();
   }
}
Core Java
There is an Inheritance as well as Composition relationship between Vehicle and Car which is not permitted
We cannot initialize the parent class instance within the constructor
Call to super is illegal
There is no problem

  Composition  Inheritance  OOPS concepts

What is the problem with this code ?

public class Car extends Vehicle{   
   int x;
   
   Car(int y){
      x = 5;
   }
   
   Car(){
      this(5);
      super();
   }
}
Core Java
We cannot overload constructors
Constructors should have type
we should have called super() before this(5)
We cannot have both super() and this() in a constructor

  Constructor  this  super

The following code is an example of

public class Car extends Vehicle{
   int x;

   Car(int y){
      x = 5;
   }

   Car(){
      this(5);
   }
}
Core Java
Constructor Overloading
Constructor Chaining
Both Constructor Overloading and Chaining
None of above

  constructor  constructor overloading  constructor chaining

Static Polymorphic in Java is achieved through .. Core Java
Method Overloading
Method Overriding
Variable Overloading
Variable Overriding

  polymorphism  static polymorphism

Runtime Polymorphism in Java is achieved through ..Core Java
Method Overloading
Method Overriding
Variable Overloading
Variable Overriding

  runtime polymorphism  polymorphism







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