Main.java Source code

Introduction

Here is the source code for Main.java

Source

//package com.java2s;
//License from project: Open Source License 

import java.util.HashMap;

import java.util.Map;
import java.util.Map.Entry;

import java.util.function.BinaryOperator;

public class Main {
    /**
     * Combines 2 maps by just adding the values of the same key together.
     *
     * @param a A map
     * @param b Another map
     * @param combiner The combiner of the values
     * @param <K> The type of the keys
     * @param <V> The type of the values
     *
     * @return a map that contains all the key of map a and b and the combined values.
     */
    public static <K, V> Map<K, V> combine(Map<? extends K, ? extends V> a, Map<? extends K, ? extends V> b,
            BinaryOperator<V> combiner) {
        Map<K, V> result = new HashMap<>();

        for (Entry<? extends K, ? extends V> entry : a.entrySet()) {
            if (b.containsKey(entry.getKey()))
                result.put(entry.getKey(), combiner.apply(entry.getValue(), b.get(entry.getKey())));
            else
                result.put(entry.getKey(), entry.getValue());
        }

        b.entrySet().stream().filter(e -> !result.containsKey(e.getKey()))
                .forEach(e -> result.put(e.getKey(), e.getValue()));

        return result;
    }

    /**
     * Combines 2 maps by just adding the values of the same key together.
     *
     * @param a A map
     * @param b Another map
     * @param <K> The type of the keys
     *
     * @return a map that contains all the key of map a and b and the combined values.
     */
    public static <K> Map<K, Integer> combine(Map<? extends K, Integer> a, Map<? extends K, Integer> b) {
        return combine(a, b, Integer::sum);
    }
}