Java 快速生成 Map

#Java 笔记

方式1：匿名内部类

import org.junit.Test;

import java.util.HashMap;
import java.util.Map;

public class MapUtilTest {


    @Test
    public void test() {
        Map<String, String> map = new HashMap<String, String>(){{
            put("k1", "v1");
            put("k2", "v2");
        }};
        System.out.println(map);
    }

}

运行结果：

{k1=v1, k2=v2}

方式2：自定义工具方法

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

public class MapUtil {

    public static class Entry<K,V> {
        private K key;
        private V val;

        public Entry(K key, V val) {
            this.key = key;
            this.val = val;
        }

        public K getKey() {
            return this.key;
        }

        public V getVal() {
            return this.val;
        }
    }

    public static <K, V> Entry<K, V> kv(K key, V val) {
        return new Entry<K, V>(key,  val);
    }

    public static <K, V> Map<K, V> map(Entry<K, V>... data) {
        return concurrentHashMap(data);
    }

    public static <K, V> HashMap<K, V> hashMap(Entry<K, V>... entries){
        HashMap<K, V> result = new HashMap<K, V>();
        putEntriesIntoMap(result, entries);
        return result;
    }

    public static <K, V> ConcurrentHashMap<K, V> concurrentHashMap(Entry<K, V>... entries){
        ConcurrentHashMap<K, V> result = new ConcurrentHashMap<K, V>();
        putEntriesIntoMap(result, entries);
        return result;
    }

    private static <K, V> void putEntriesIntoMap(Map<K,V> map, Entry<K, V>[] entries) {
        for(Entry<K, V> item : entries){
            map.put(item.getKey(), item.getVal());
        }
    }

}

import org.junit.Test;

import java.util.Map;

import static MapUtil.kv;

public class MapUtilTest {

    @Test
    public void test() {
        Map<String, String> map = MapUtil.hashMap(
                kv("k1", "v1"),
                kv("k2", "v2")
        );
        System.out.println(map);
    }

}

运行结果：

{k1=v1, k2=v2}

( 本文完 )