If you'd like to print this:

One Two Three Four
 1   2    3    4  

using this:

new Columns()
    .withColumnSeparator(" ")
    .withPad(" ")
    .alignCenter()
    .addLine("One", "Two", "Three", "Four")
    .addLine("1", "2", "3", "4")
    .print()
;

all you need is this:

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;  
import java.util.function.BiFunction;

public class Columns {

    List<List<String>> lines = new ArrayList<>();
    List<Integer> maxLengths = new ArrayList<>();
    int numColumns;
    int oldLength;
    boolean firstCall = true;
    String columnSeparator = " ";
    String pad = " ";
    BiFunction<String, String, String> align = (word, pad) -> word += pad;

    public Columns addLine(String... line) {

        if (firstCall){
            for(int column = 0; column < line.length; column++) {
                maxLengths.add(0);
            }
            oldLength = line.length;
        }
        
        if (oldLength != line.length) {
            throw new IllegalArgumentException();
        }

        for(int column = 0; column < line.length; column++) {
            int length = Math
                .max( 
                    maxLengths.get(column), 
                    line[column].length() 
                )
            ;
            maxLengths.set( column, length );
        }

        lines.add( Arrays.asList(line) );
        firstCall = false;
        return this;
    }

    public void print(){
        System.out.println( toString() );
    }

    public String toString(){
        String result = "";
        for(List<String> line : lines) {
            for(int column = 0; column < line.size(); column++) {
                result += pad( line.get(column), maxLengths.get(column) );
                if (column < line.size() - 1) { 
                    result += columnSeparator; 
                }
            }
            result += System.lineSeparator();
        }
        return result;
    }

    private String pad(String word, int newLength){
        while (word.length() < newLength) {
            word = align.apply(word, pad);
        }       
        return word;
    }

    public Columns withColumnSeparator(String columnSeparator){
        this.columnSeparator = columnSeparator;
        return this;
    }
        
    public Columns withPad(String pad){
        this.pad = pad;
        return this;
    }
    
    public Columns alignLeft(){
        align = (word, pad) -> word = word + pad;
        return this;
    }

    public Columns alignRight(){
        align = (word, pad) -> word = pad + word;
        return this;
    }

    public Columns alignCenter(){
        align = (word, pad) -> {
            return (word.length() % 2 == 0) 
                ? pad + word
                : word + pad
            ;
        };
        return this;
    }
}

but is that as good as it could be? Looking for a code review to reveal problems. Anything from better names to fewer bugs to better ideas.