How to find Leader Numbers from the given array of Integers ?

package pack1;

import java.util.List;

public interface LeaderIntf {
	
	/* Define the functional interface with SAM 'RdInputArray' */
	public List<Integer> RdInputArray(Integer[] arrayNums);

	/* Define the static method 'displayMsg' */
	static void displayMsg(List<Integer> leaderArray) {

		System.out.println("The leaders numbers from the given array");
		System.out.println(leaderArray);
	}
}

package pack1;

import java.util.ArrayList;
import java.util.List;
import java.util.Optional;
import java.util.logging.Logger;
import java.util.stream.IntStream;

class ReadInputArrayNums {

	private Integer[] inputArrayNums;

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

	public boolean validateInputs(Integer[] inputArrayNums) {

		/* 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[]> inputArrayVals= Optional.ofNullable(inputArrayNums);

		/*
		 * Fetch the value of the Optional Integer Array of inputArrayNums 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 (inputArrayVals.isPresent()) {
			if (inputArrayNums.length != 0)
				setInputArrayNums(inputArrayVals.get());
			else
				return false;
		} else
			return false;

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

	/* Define getter and setters for an inputArrayNums array values */
	public Integer[] getInputArrayNums() {
		return inputArrayNums;
	}

	public void setInputArrayNums(Integer[] inputArrayNums) {
		this.inputArrayNums = inputArrayNums;
	}
}

class LeaderNumbers_Using_Array_Backward extends ReadInputArrayNums implements LeaderIntf {

	public List<Integer> RdInputArray(Integer[] inpVal) {

		/* Fetch the class object's name from which this method is called */
		String cName = Thread.currentThread().getStackTrace()[2].getClassName();
		String mName = "RdInputArray";
		logger.info("This method '" + mName + "' called from the Class '" + cName + "'");
		
		List <Integer> leaderNumsList = new ArrayList<Integer>();
		if (validateInputs(inpVal)) {

			int leadNum = getInputArrayNums()[getInputArrayNums().length - 1];
			 
	        // Processing the numbers in the backward direction
			leaderNumsList.add(leadNum);
	 
	        /*
	         * For each number from the backside of the array checking whether it's left
	         * side number is large
	         */
	        for (int k = getInputArrayNums().length - 1; k >= 0; k--) {
	            if (getInputArrayNums()[k] > leadNum) {
	                leadNum = getInputArrayNums()[k];
	                leaderNumsList.add(leadNum);
	            }
	        }
		} else
			logger.info("The given Input Array numbers are null");

		LeaderIntf.displayMsg(leaderNumsList);
		return leaderNumsList;
	}
}

class LeaderNumbers_Using_Array_Forward extends ReadInputArrayNums implements LeaderIntf {

	public List<Integer> RdInputArray(Integer[] inpVal) {

		/* Fetch the class object's name from which this method is called */
		String cName = Thread.currentThread().getStackTrace()[2].getClassName();
		String mName = "RdInputArray";
		logger.info("This method '" + mName + "' called from the Class '" + cName + "'");
		
		List <Integer> leaderNumsList = new ArrayList<Integer>();
		if (validateInputs(inpVal)) {

			 for (int i = 0; i < getInputArrayNums().length; i++) {
		            int j;
		            /*
		             * For each number from the frontside of the array checking whether it's right
		             * side number is less
		             */
		            for (j = i + 1; j < getInputArrayNums().length; j++) {
		                if (getInputArrayNums()[i] < getInputArrayNums()[j])
		                    break;
		            }
		 
		            if (j == getInputArrayNums().length)
		                leaderNumsList.add(getInputArrayNums()[i]);
		        	
		        }
		} else
			logger.info("The given Input Array numbers are null");

		LeaderIntf.displayMsg(leaderNumsList);
		return leaderNumsList;
	}
}

class LeaderNumbers_Using_Streams extends ReadInputArrayNums implements LeaderIntf {

	public List<Integer> RdInputArray(Integer[] inpVal) {

		/* Fetch the class object's name from which this method is called */
		String cName = Thread.currentThread().getStackTrace()[2].getClassName();
		String mName = "RdInputArray";
		logger.info("This method '" + mName + "' called from the Class '" + cName + "'");
		
		List <Integer> leaderNumsList = new ArrayList<Integer>();
		if (validateInputs(inpVal)) {

		IntStream.range(0, getInputArrayNums().length)
					.map(j -> getInputArrayNums().length - j - 1)
						.filter(k -> getInputArrayNums()[k] >= getInputArrayNums()[getInputArrayNums().length - 1])
							.forEach(x -> leaderNumsList.add(getInputArrayNums()[x]));
			
		} else
			logger.info("The given Input Array numbers are null");

		LeaderIntf.displayMsg(leaderNumsList);
		return leaderNumsList;
	}
}


public class LeaderNumsJ8 {
	
	public static void main(String args[]) {
		 
         /*
		 * create the class object LeaderNumbers_Using_Array_Backward, and call the method
		 * RdInputArray
		 */
		Integer[] arrNums = { 10, 2, 41, 13, 8, 36, 7, 15, 21 };
		LeaderNumbers_Using_Array_Backward LNUAB = new LeaderNumbers_Using_Array_Backward();
        LNUAB.RdInputArray(arrNums);
        
        /*
		 * create the class object LeaderNumbers_Using_Array_Forward, and call the method
		 * RdInputArray
		 */
     	LeaderNumbers_Using_Array_Forward LNUAF = new LeaderNumbers_Using_Array_Forward();
        LNUAF.RdInputArray(arrNums);
		
        /*
		 * create the class object LeaderNumbers_Using_Streams, and call the method
		 * RdInputArray
		 */
     	LeaderNumbers_Using_Streams LNUS = new LeaderNumbers_Using_Streams();
        LNUS.RdInputArray(arrNums);
	}
}