JAVA Interfaces and Abstract Classes In Java, declaring a class abstract is useful When default implementations of some methods are not desirable. When it makes sense to have objects of that class. To prevent developers from further extending the class. To force developers to extend the class not to use its capabilities. When it doesn't make sense to have objects of that class. When default implementations of some methods are not desirable. When it makes sense to have objects of that class. To prevent developers from further extending the class. To force developers to extend the class not to use its capabilities. When it doesn't make sense to have objects of that class. ANSWER DOWNLOAD EXAMIANS APP
JAVA Interfaces and Abstract Classes Determine output of the following code.interface A { }class C { }class D extends C { }class B extends D implements A { }public class Test extends Thread{ public static void main(String[] args){ B b = new B(); if (b instanceof A) System.out.println("b is an instance of A"); if (b instanceof C) System.out.println("b is an instance of C"); }} b is an instance of A followed by b is an instance of b is an instance of b is an instance of Nothing. b is an instance of A followed by b is an instance of b is an instance of b is an instance of Nothing. ANSWER DOWNLOAD EXAMIANS APP
JAVA Interfaces and Abstract Classes What happens if the following program is compiled and executed?interface MyInterface{ void display();}interface MySubInterface extends MyInterface{ void display();}public class Test implements MySubInterface{ public void display(){ System.out.print("Welcome to Examveda."); } public static void main(String args[]){ Test t = new Test(); t.display(); }} The code will lead to a compilation error as the display method is not declared as abstract. The code will compile and execute successfully showing the output Welcome to Examians. The code will lead to a compilation error as declaration of the display method has been provided in two interface. None of these The code will lead to a compilation error due to public modifier while declaring the display method. The code will lead to a compilation error as the display method is not declared as abstract. The code will compile and execute successfully showing the output Welcome to Examians. The code will lead to a compilation error as declaration of the display method has been provided in two interface. None of these The code will lead to a compilation error due to public modifier while declaring the display method. ANSWER DOWNLOAD EXAMIANS APP
JAVA Interfaces and Abstract Classes Suppose A is an abstract class, B is a concrete subclass of A, and both A and B have a default constructor. Which of the following is correct?1. A a = new A();2. A a = new B();3. B b = new A();4. B b = new B(); 2 and 4 3 and 4 1 and 2 1 and 3 2 and 3 2 and 4 3 and 4 1 and 2 1 and 3 2 and 3 ANSWER DOWNLOAD EXAMIANS APP
JAVA Interfaces and Abstract Classes Which of the following class definitions defines a legal abstract class? class A { abstract void unfinished(); } class A { abstract void unfinished() { } } public class abstract A { abstract void unfinished(); } abstract class A { abstract void unfinished(); } class A { abstract void unfinished(); } class A { abstract void unfinished() { } } public class abstract A { abstract void unfinished(); } abstract class A { abstract void unfinished(); } ANSWER DOWNLOAD EXAMIANS APP
JAVA Interfaces and Abstract Classes What will happen after compiling this program code?abstract class MyClass{ //line 1 private int a, b; public void call(int a, int b){ this.a = a; this.b = b; System.out.print(a+b); }}public class Test{ public static void main(String args[]){ MyClass m = new MyClass(); //line 2 m.call(12,25); }} None of these Compilation error due to line 1 Runtime error Successful run and print 37 Compilation error due to line 2 None of these Compilation error due to line 1 Runtime error Successful run and print 37 Compilation error due to line 2 ANSWER DOWNLOAD EXAMIANS APP
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