Frequently Asked Core Java Interview Questions and Answers

Here is a few questions that I find it useful for preparing the interviews (Java).

A few thing you have to know first:

• It is possible to have more than one class in a single Java file but only 1 public class is allowed.
• It is possible to have a main method in each class
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class A         {             public static void main(String…s)             {             }                         public static void main(int…s)             {             }         }

		class A
		{
			public static void main(String…s)
			{
			}
			
			public static void main(int…s)
			{
			}
		}

Question 1: Can we invoke main method explicitly?
Answer: Of course

Example:

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        class A
        {
            public static void main(String…s)
            {
                System.out.println(“Hello”);
            }
 
            Class B
            {
                public static void main(String…s)
                {
                    A.main();
                }
            }
        }

		class A
		{
			public static void main(String…s)
			{
				System.out.println(“Hello”);
			}

			Class B
			{
				public static void main(String…s)
				{
					A.main();
				}
			}
		}

Question 2: Can we execute the Java program without main method?
Answer: Yes

Example:

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        class A
        {
            static
            {
                System.out.println(“HelloACM.com”);
            }
        }

		class A
		{
			static
			{
				System.out.println(“HelloACM.com”);
			}
		}

Question 3: What is difference between object and class?
Answer: A object is an instance of the class. The class can be considered as [skeleton] or [template] of the objects.

Question 4: Why character cosumes 2 bytes in java?
Answer: Java support UNICODE and for UNICODE 2 bytes are used.

Question 5: Why the [main] method is static?
Answer: Static main function is the entry of the Java application. Every object has the same entry.

Question 6: When the constructor is called?
Answer: When an object is created.

Question 7: Inheritance occurs at runtime?
Answer: Yes

Question 8: What is the purpose of using dynamic binding?
Answer: To achieve abstraction.

Question 9: Is constructor allowed in abstract class?
Answer: Yes

Question 10: Is it allowed to have a static abstract method?
Answer: No

Question 11: How to invoke the abstract class method?
Answer: The dynamic binding.

Example:

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base b = new child();

base b = new child();

–EOF (The Ultimate Computing & Technology Blog) —