How to find the nth Fibonacci number in the series?

package pack1;

public interface NthFibonacciIntf {

	/* Define the functional interface with SAM 'RdInput' */
	public Integer RdInput(Integer intVal);

	/* Define the static method 'displayMsg' */
	static void displayMsg(Integer inpVal, Integer nthFib) {

		if (nthFib == 0)
			System.out.println("Nth Fibonacci of " + inpVal + "  not exists");
		else
			System.out.println("Nth Fibonacci of " + inpVal + " is " + nthFib);

		System.out.println();
	}
}

package pack1;

import java.util.List;
import java.util.Optional;
import java.util.logging.Logger;
import java.util.stream.Collectors;
import java.util.stream.Stream;

class ReadInputNthNum {

	private Integer inputIntvalue;

	/* Declare the logger object for the class to display the log messages */
	static Logger logger = Logger.getLogger(ReadInputNthNum.class.getName());

	public boolean validateInputs(Integer inputAnInteger) {

		/* Fetch the class object's name from which this method is called */
		String cName = Thread.currentThread().getStackTrace()[2].getClassName();
		String mName = "validateInputs()";
		logger.info("This method '" + mName + "' called from the Class '" + cName + "'");

		/* Validating the function parameters using Optional Integer Array data type */
		Optional<Integer> inputVal = Optional.ofNullable(inputAnInteger);

		/*
		 * Fetch the value of the Optional Integer inputAnInteger using 'isPresent'
		 * condition check. If the value is available use 'get' method otherwise simply
		 * return 'false' to stop the program execution without proceeding further.
		 */
		if (inputVal.isPresent()) {
			setInputIntvalue(inputVal.get());
			System.out.println("The given number is " + getInputIntvalue());
		} else
			return false;

		logger.info("The provided Input validated Successfully");
		return true;
	}

	/* Define getter and setters for an inputIntvalue BigInteger variable */
	public Integer getInputIntvalue() {
		return inputIntvalue;
	}

	public void setInputIntvalue(Integer inputIntvalue) {
		this.inputIntvalue = inputIntvalue;
	}
}

class NthFibonacci_Using_CoreLogic extends ReadInputNthNum implements NthFibonacciIntf {

	public Integer RdInput(Integer inpVal) {

		/* Fetch the class object's name from which this method is called */
		String cName = Thread.currentThread().getStackTrace()[2].getClassName();
		String mName = "RdInput";
		logger.info("This method '" + mName + "' called from the Class '" + cName + "'");

		/* Define a BigInteger variable and initialize factValue value to 1 */
		int nthFib = 0;

		if (validateInputs(inpVal))

			if (getInputIntvalue() >= 0) {
				nthFib = NthFib(getInputIntvalue());
			} else
				logger.info("The given Input number is null");

		NthFibonacciIntf.displayMsg(inpVal, nthFib);
		return nthFib;

	}

	private static int NthFib(int nthNum) {

		int[] fib = new int[nthNum];

		if (nthNum == 0 || nthNum == 1)
			return nthNum;
		else {
			// Initialize the first two values in the Fibonacci series
			fib[0] = 0;
			fib[1] = 1;

			// Evaluate each term in the series until the nthNum
			for (int i = 2; i < nthNum; i++)
				fib[i] = fib[i - 1] + fib[i - 2];
			return fib[nthNum - 1];
		}
	}
}

class NthFibonacci_Using_Recursion extends ReadInputNthNum implements NthFibonacciIntf {

	public Integer RdInput(Integer inpVal) {

		/* Fetch the class object's name from which this method is called */
		String cName = Thread.currentThread().getStackTrace()[2].getClassName();
		String mName = "RdInput";
		logger.info("This method '" + mName + "' called from the Class '" + cName + "'");

		/* Define a BigInteger variable and initialize factValue value to 1 */
		int nthFib = 0;

		if (validateInputs(inpVal))

			if (getInputIntvalue() > 0) {
				nthFib = NthFibRecursion(getInputIntvalue() - 1);
			} else
				logger.info("The given Input number is null");

		NthFibonacciIntf.displayMsg(inpVal, nthFib);
		return nthFib;

	}

	private static int NthFibRecursion(int nthNum) {

		// Exit criteria of this recursive function when the parameter value reaches 0
		// or 1.

		if (nthNum == 0 || nthNum == 1)
			return nthNum;
		else
			/*
			 * Recursive calls to NthFib() with n-1 and n-2 as a parameter values. The
			 * following recursive calls will update the parameter values as per the
			 * Fibonacci series logic
			 */

			return (NthFibRecursion(nthNum - 1) + NthFibRecursion(nthNum - 2));
	}

}

class NthFibonacci_Using_StreamAPI extends ReadInputNthNum implements NthFibonacciIntf {

	public Integer RdInput(Integer inpVal) {

		/* Fetch the class object's name from which this method is called */
		String cName = Thread.currentThread().getStackTrace()[2].getClassName();
		String mName = "RdInput";
		logger.info("This method '" + mName + "' called from the Class '" + cName + "'");

		/* Define an int variable and initialize nthFib value to 0 */
		int nthFib = 0;

		if (validateInputs(inpVal)) {

			if (getInputIntvalue() == 0 || getInputIntvalue() == 1)
				return getInputIntvalue();

			if (getInputIntvalue() >= 0) {
				List<Integer> fibSeries = Stream.iterate(new int[] { 0, 1 }, t -> new int[] { t[1], t[0] + t[1] })
						.limit(getInputIntvalue()).map(k -> k[0]).collect(Collectors.toList());
				nthFib = fibSeries.get(getInputIntvalue() - 1);
			}
		} else
			logger.info("The given Input number is null");

		NthFibonacciIntf.displayMsg(inpVal, nthFib);
		return nthFib;
	}

}

public class NthFibonacciJ8 {

	public static void main(String args[]) {

		/*
		 * create the class object NthFibonacci_Using_CoreLogic, and call the method
		 * RdInput
		 */

		NthFibonacci_Using_CoreLogic NFUCL = new NthFibonacci_Using_CoreLogic();
		NFUCL.RdInput(-16);
		NFUCL.RdInput(null);

		/*
		 * create the class object NthFibonacci_Using_CoreLogic, and call the method
		 * RdInput
		 */

		NthFibonacci_Using_Recursion NFUR = new NthFibonacci_Using_Recursion();
		NFUR.RdInput(10);
		NFUR.RdInput(null);

		/*
		 * create the class object NthFibonacci_Using_CoreLogic, and call the method
		 * RdInput
		 */

		NthFibonacci_Using_StreamAPI NFUSA = new NthFibonacci_Using_StreamAPI();
		NFUSA.RdInput(10);
		NFUSA.RdInput(null);
	}
}