A simple generic tuple (key/value pair) builder with the ability to dynamically filter out null values when trying to add them.

TupleListBuilder.java

import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.List;

/**
 *
 * This class serves as a generic approach to create list containing related key value tuples
 * represented within a list while offering the functionality to be able to dynamically filter out (don't add)
 * entries where the value would be null as need for some use cases.
 *
 * The skip mechanism is backed up by the following truth table:
 * <p>
 * Entry value is null? => V
 * Global skip (skipNullValues set to true) => G
 * Explicit skip (skipNullValue set to true) => E
 * Resulting in an entry addition => A
 * <p>
 * | V | G | E || A
 * -----------------
 * | 0 | 0 | 0 || 1
 * | 0 | 0 | 1 || 1
 * | 0 | 1 | 0 || 1
 * | 0 | 1 | 1 || 1
 * | 1 | 0 | 0 || 1
 * | 1 | 0 | 1 || 0
 * | 1 | 1 | 0 || 1
 * | 1 | 1 | 1 || 0
 * <p>
 * => Addition when !(V&&E)
 */
public abstract class TupleListBuilder<K, V extends K> {
    private final boolean skipNullValues;
    private final List<K> keyValueTupleList = new ArrayList<>();

    public TupleListBuilder() {
        this(true);
    }

    public TupleListBuilder(boolean skipNullValues) {
        this.skipNullValues = skipNullValues;
    }

    public TupleListBuilder<K, V> setTag(K key, V value) {
        return this.setTag(key, value, this.skipNullValues);
    }

    public TupleListBuilder<K, V> setTag(K key, V value, boolean skipNullValue) {
        if (!(value == null && skipNullValue)) {
            synchronized (keyValueTupleList) {
                this.keyValueTupleList.add(key);
                this.keyValueTupleList.add(value);
            }
        }
        return this;
    }

    public List<K> build() {
        return new ArrayList<>(this.keyValueTupleList);
    }

    @SuppressWarnings("unchecked")
    public K[] buildArray() {
        if(this.keyValueTupleList.isEmpty()){
            return (K[]) new Object[0];
        }
        K[] tupleArray = (K[]) Array.newInstance(this.keyValueTupleList.get(0).getClass(), this.keyValueTupleList.size());
        for (int i = 0; i < this.keyValueTupleList.size(); i++) {
            tupleArray[i] = this.keyValueTupleList.get(i);
        }
        return tupleArray;
    }
}