JAVA Interfaces and Abstract Classes
In Java, declaring a class abstract is useful

When default implementations of some methods are not desirable.
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 it makes sense to have objects of that class.
To prevent developers from further extending the class.

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JAVA Interfaces and Abstract Classes
Which of the following statements regarding abstract classes are true?

An abstract class can be extended.
A subclass can override a concrete method in a superclass to declare it abstract.
All of these
A subclass of a non-abstract superclass can be abstract.
An abstract class can be used as a data type.

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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(); }}

Program will compile and execute successfully and prints
Program compiles but leads to runtime exception.
Compilation error as class can not be declared as abstract.
Compilation error occurs as the abstract class TestAbstract contains a non-abstract method.
None of these

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JAVA Interfaces and Abstract Classes
interface Base{ boolean m1 (); byte m2(short s);}which two code fragments will compile?1. interface Base2 implements Base {}2. abstract class Class2 extends Base { public boolean m1(){ return true; }}3. abstract class Class2 implements Base {}4. abstract class Class2 implements Base { public boolean m1(){ return (7 > 4); }}5. abstract class Class2 implements Base { protected boolean m1(){ return (5 > 7) }}

1 and 2
3 and 4
4 and 5
2 and 3
1 and 3

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