JAVA Interfaces and Abstract Classes In Java, declaring a class abstract is useful To prevent developers from further extending the class. 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 force developers to extend the class not to use its capabilities. To prevent developers from further extending the class. 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 force developers to extend the class not to use its capabilities. 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 Nothing. b is an instance of b is an instance of b is an instance of A followed by b is an instance of Nothing. b is an instance of b is an instance of 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(); 1 and 3 1 and 2 2 and 4 3 and 4 2 and 3 1 and 3 1 and 2 2 and 4 3 and 4 2 and 3 ANSWER DOWNLOAD EXAMIANS APP
JAVA Interfaces and Abstract Classes What will be the output when the following program is compiled and executed?abstract class TestAbstract{ String my_name; String myName(){ my_name = "Examveda"; return my_name; } abstract void display();}public class Test extends TestAbstract{ void display(){ String n = myName(); System.out.print("My name is "+ n); } public static void main(String args[]){ Test t = new Test(); t.display(); }} None of these Program will compile and execute successfully and prints Compilation error occurs as the abstract class TestAbstract contains a non-abstract method. Compilation error as class can not be declared as abstract. Program compiles but leads to runtime exception. None of these Program will compile and execute successfully and prints Compilation error occurs as the abstract class TestAbstract contains a non-abstract method. Compilation error as class can not be declared as abstract. Program compiles but leads to runtime exception. ANSWER DOWNLOAD EXAMIANS APP
JAVA Interfaces and Abstract Classes Given the following piece of code:public class School{ public abstract double numberOfStudent();}which of the following statements is true? The method numberOfStudent() in class School must have a body. You must add a return statement in method numberOfStudent(). Class School must be defined abstract. The keywords public and abstract cannot be used together. The method numberOfStudent() in class School must have a body. You must add a return statement in method numberOfStudent(). Class School must be defined abstract. The keywords public and abstract cannot be used together. 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); }} Runtime error Successful run and print 37 Compilation error due to line 1 None of these Compilation error due to line 2 Runtime error Successful run and print 37 Compilation error due to line 1 None of these Compilation error due to line 2 ANSWER DOWNLOAD EXAMIANS APP
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