Question1: Which two statements are true about Java byte code? (Choose two.)

A. It can be serialized across network.
B. It can run on any platform that has a Java compiler.
C. It can run on any platform.
D. It has “.java” extension.
E. It can run on any platform that has the Java Runtime Environment.

Answer: A,E

Question2: Given below:

public interface Readable {
	public void readBook();
	public void setBookMark();
}
public abstract class Book implements Readable { // Line N1
	public void readBook() {
	
	}
      //Line N2
}
public class EBook extends Book { //Line N3

	public void readBook() {
		System.out.println("ebook");

	}
        //Line N4
	public static void main(String[] args) {
		Book book1 = new EBook();
		book1.readBook();
	}
	
}

Which Option enables the code to compile:

A. Replace the code at line N1 with class Book implements Runnable{
B. At Line N2, Insert public abstract void setBookMark()
C. Replace the code at Line N3 with abstract class EBook extends Book{
D. At Line N4, insert public void setBookMark()

Answer: D

Question3: Given below code:

	public static void main(String[] args) {
		Short s1 = 200;
		Integer s2 = 400;
		Long s3 = (long)s1+s2; // Line N1
		String s4 = (String)(s3*s2); // Line N2
		System.out.println("Sum is"+s4);
	}

What is the result?
A. Sum is 600
B. Compilation fails at line n1.
C. Compilation fails at line n2.
D. A ClassCastException is thrown at line n1.
E. A ClassCastException is thrown at line n2.

Answer: C . It will give compilation error that “can not cast from long to String”

Question4: Given below code: Which two class definitions fail to compile? (Choose two.)

abstract class A3 {
	private static int i;
	public void doStuff() {}
	public A3() {	}
}
final class A1 {
	public A1() {
		
	}
}
private class A2 {
	private static int i;
	private A2() {}
}
class A4 {
	protected static final int i = 10;
	private A4() {
	}
}
  
final abstract class A5 {
   protected static int i;
   void doStuff() {};
   abstract void doIt();
}

A. A1
B. A2
C. A3
D. A4
E. A5
Answer: B , E
Explanation: Class A2 and A5 are failed to compile

A1 Class : Illegal modifier for the class A2; only public, abstract & final are permitted
A5 Class: The class A5 can be either abstract or final, not both

Question5: Give the below code:

public class A {
	public void test() {
		System.out.println("A");
	}
}
public class B extends A{
	public void test() {
		System.out.println("B");
	}
}
public class C extends A {
	public void test() {
		System.out.println("A");
	}
	public static void main(String[] args) {
		A b1 = new A();
		A b2 = new C();
		b1 = (A)b2; // Line N1
		A b3 = (B) b2; // Line N2
		b1.test();
		b3.test();
	}
}

What is the result?
A. AB
B. AC
C. CC
D. A ClassCastException is thrown only at line n1.
E. A ClassCastException is thrown only at line n2.

Answer: E

Exception in thread “main” java.lang.ClassCastException: class inheritanceeg.C cannot be cast to class inheritanceeg.B (inheritanceeg.C and inheritanceeg.B are in module TestJavaSE of loader ‘app’)
at TestJavaSE/inheritanceeg.C.main(C.java:11)

Question6: Given below code:

	public static void main(String[] args) {
		ArrayList<Integer> points = new ArrayList<Integer>();
		points.add(1);
		points.add(2);
		points.add(3);
		points.add(4);
		points.add(null);
		points.remove(1);
		points.remove(null);
		System.out.println(points);
	}

What is the result?
A. A NullPointerException is thrown at runtim
B. [1, 2, 4]
C. [1, 2, 4, null]
D. [1, 3, 4, null]
E. [1, 3, 4]
F. Compilation fails.
Answer: E

  • remove(1) -> removes at index1 which is element 2
  • remove(null) -> This removes object from list so it will remove null object
Explanation:

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