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.Arrays;
import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;

import java.util.function.Function;

import java.util.stream.Collectors;

public class Main {
    public static <T, K, V> HashMap<K, HashSet<V>> group(Collection<T> entities, Function<T, K> keyMapper,
            Function<T, V> valueMapper) {
        return entities.stream().collect(Collectors.groupingBy(keyMapper, HashMap::new,
                Collectors.mapping(valueMapper, Collectors.toCollection(HashSet::new))));
    }

    public static <T, K, V> HashMap<K, HashSet<V>> group(T[] entities, Function<T, K> keyMapper,
            Function<T, V> valueMapper) {
        return group(Arrays.asList(entities), keyMapper, valueMapper);
    }
}