Merge two map counters. - Java java.util

Description

Merge two map counters.

Demo Code

//package com.java2s;

import java.util.Map;

public class Main {
    /** Merge two map counters. */
    public static <K> void mergeMapCounters(Map<K, Integer> counter1,
            Map<K, Integer> counter2) {
        for (K key : counter2.keySet()) {
            increaseMapCounter(counter1, key, counter2.get(key));
        }/*from w  w w. j a va 2 s .c o m*/
    }

    /**
     * Increase counter.get(key) by increase.
     * If value decrease to zero, it is removed from map.
     */
    public static <K> void increaseMapCounter(Map<K, Integer> counter,
            K key, int increase) {
        if (!counter.containsKey(key)) {
            counter.put(key, 0);
        }
        counter.put(key, counter.get(key) + increase);
        if (counter.get(key) == 0) {
            counter.remove(key);
        }
    }
}

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