package innovimax.mixthem.join;

import innovimax.mixthem.exceptions.MixException;
import innovimax.mixthem.interfaces.IJoinLine;

import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

/**
* <p>Joins two lines on a common field.</p>
* <p>This is the default implementation of IJoinLine.</p>
* @see IJoinLine
* @author Innovimax
* @version 1.0
*/
public class DefaultLineJoining implements IJoinLine {
	
	@Override
	public String join(String line1, String line2, JoinType type, List<String> params) throws MixException {
		String join = null;
		if (line1 != null && line2 != null) {
			List<String> list1 = Arrays.asList(line1.split("\\s"));
			List<String> list2 = Arrays.asList(line2.split("\\s"));
			switch (type) {
				case _DEFAULT:				
					if (list1.size() > 0 && list2.contains(list1.get(0))) {
						String part1 = list1.stream().collect(Collectors.joining(" "));
						String part2 = list2.stream().filter(s -> !list1.contains(s)).collect(Collectors.joining(" "));
						join = part1 + " " + part2;
					}				
					break;
				case _SAME_COL:		
					int index;
					try {
						index = Integer.parseInt(params.get(0));
					} catch (NumberFormatException e) {
						throw new MixException("Unexpected join parameter value: " + params.get(0), e);
					}
					if (list1.size() >= index && list2.size() >= index && list1.get(index - 1).equals(list2.get(index - 1))) {
						String part1 = list1.get(index - 1);
						String part2 = list1.stream().filter(s -> !s.equals(part1)).collect(Collectors.joining(" "));
						String part3 = list2.stream().filter(s -> !list1.contains(s)).collect(Collectors.joining(" "));
						join = part1 + " " + part2 + " " + part3;				
					}
					break;
				case _DIFF_COL:
					System.out.println("join col1 col2 todo");
					break;
			}
		}
		return join;
	}
	
}

package innovimax.mixthem.join;

import innovimax.mixthem.exceptions.MixException;
import innovimax.mixthem.interfaces.IJoinLine;

import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

/**
* <p>Joins two lines on a common field.</p>
* <p>This is the default implementation of IJoinLine.</p>
* @see IJoinLine
* @author Innovimax
* @version 1.0
*/
public class DefaultLineJoining implements IJoinLine {
	
	@Override
	public String join(String line1, String line2, JoinType type, List<String> params) throws MixException {
		String join = null;
		if (line1 != null && line2 != null) {
			List<String> list1 = Arrays.asList(line1.split("\\s"));
			List<String> list2 = Arrays.asList(line2.split("\\s"));
			switch (type) {
				case _DEFAULT:				
					if (list1.size() > 0 && list2.contains(list1.get(0))) {
						String part1 = list1.stream().collect(Collectors.joining(" "));
						String part2 = list2.stream().filter(s -> !list1.contains(s)).collect(Collectors.joining(" "));
						join = part1 + " " + part2;
					}				
					break;
				case _SAME_COL:		
					int index;
					try {
						index = Integer.parseInt(params.get(0));
					} catch (NumberFormatException e) {
						throw new MixException("Unexpected join parameter value: " + params.get(0), e);
					}
					if (list1.size() >= index && list2.size() >= index && list1.get(index - 1).equals(list2.get(index - 1))) {
						String part1 = list1.get(index - 1);
						String part2 = list1.stream().filter(s -> !s.equals(part1)).collect(Collectors.joining(" "));
						String part3 = list2.stream().filter(s -> !list1.contains(s)).collect(Collectors.joining(" "));
						join = part1 + " " + part2 + " " + part3;				
					}
					break;
				case _DIFF_COL:
					int col1, col2;
					try {
						col1 = Integer.parseInt(params.get(0));
						col2 = Integer.parseInt(params.get(1));
					} catch (NumberFormatException e) {
						throw new MixException("Unexpected join parameter value: " + params.toString(), e);
					}
					if (list1.size() >= index && list2.size() >= index && list1.get(col1 - 1).equals(list2.get(col2 - 1))) {
						String part1 = list1.get(col1 - 1);
						String part2 = list1.stream().filter(s -> !s.equals(part1)).collect(Collectors.joining(" "));
						String part3 = list2.stream().filter(s -> !list1.contains(s)).collect(Collectors.joining(" "));
						join = part1 + " " + part2 + " " + part3;				
					}
					break;
			}
		}
		return join;
	}
	
}

Update DefaultLineJoining.java