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  • 如何初始化Map,java

     原来路径:https://www.itranslater.com/qa/details/2104117160695038976

    java - 如何初始化静态Map?

    import com.google.common.collect.ImmutableMap;
    
    import java.util.AbstractMap.SimpleEntry;
    import java.util.Arrays;
    import java.util.HashMap;
    import java.util.Map;
    import java.util.stream.Collectors;
    import java.util.stream.Stream;
    
    /**
     * @Auther: Liruilong
     * @Date: 2020/7/25 13:40
     * @Description:
     */
    public class test {
    
        // 静态Map的初始化,实际情况中,可以使用枚举代替
        // 方法一
        public static final Map<Integer, String> myMap_0 = new HashMap<Integer, String>();
    
        static {
            myMap_0.put(1, "one");
            myMap_0.put(2, "two");
        }
        // 方法二 JDK5
        public static final Map<Integer, String> myMap_1 = new HashMap<Integer, String>() {{
            put(1, "one");
            put(2, "two");
        }};
        // 方法三  Guava
        static final Map<Integer,String> myMap_2 = ImmutableMap.<Integer, String> builder().put(1, "one").put(2, "two").build();
    
        // 方法四,不超过5个的时候  Guava
        static final Map<Integer, String> myMap_3 = ImmutableMap.of(
            1, "one",
            2, "two"
        );
    
        // 方法五  Collections.unmodifiableMap()  通过工具类实现
    
    
        // 方法六 JDK8
        static final Map<Integer, String> MY_MAP = Arrays.stream(new Object[][]{
            {1, "one"},
            {2, "two"},
        }).collect(Collectors.toMap(kv -> (Integer) kv[0], kv -> (String) kv[1]));
    
    
        private static final Map<Integer, String> myMap = Stream.of(
            new SimpleEntry<>(1, "one"),
            new SimpleEntry<>(2, "two"),
            new SimpleEntry<>(3, "three"),
            new SimpleEntry<>(4, "four"),
            new SimpleEntry<>(5, "five"),
            new SimpleEntry<>(6, "six"),
            new SimpleEntry<>(7, "seven"),
            new SimpleEntry<>(8, "eight"),
            new SimpleEntry<>(9, "nine"),
            new SimpleEntry<>(10, "ten"))
            .collect(Collectors.toMap(SimpleEntry::getKey, SimpleEntry::getValue));
    
    }
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  • 原文地址:https://www.cnblogs.com/liruilong/p/13376773.html
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