Java 静态(static) Map字典初始化方法及示例代码

1､使用静态代码块初始化

public class Test {    private static final Map myMap;    static {        Map aMap = HashMap();        aMap.put(1, "one");        aMap.put(2, "two");        myMap = Collections.unmodifiableMap(aMap);    }}

2､使用static静态方法初始化

public class Test {    private static final Map MY_MAP = createMap();    private static Map createMap() {        Map result = new HashMap<>();        result.put(1, "one");        result.put(2, "two");        return Collections.unmodifiableMap(result);    }}

3､使用Map.ofEntries初始化(Java 9+)

文档：

Map.ofEntries

Map.entry( k , v )

import static java.util.Map.entry;private static final Map map = Map.ofEntries(        entry(1, "one"),        entry(2, "two"),        entry(3, "three"),        entry(4, "four"),        entry(5, "five"),        entry(6, "six"),        entry(7, "seven"),        entry(8, "eight"),        entry(9, "nine"),        entry(10, "ten"));

4､使用Stream.of()和SimpleImmutableEntry初始化(Java 8+)

文档：

SimpleEntry

SimpleImmutableEntry

import java.util.AbstractMap.*;private static final Map 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));

5､使用Map.of实现静态Map初始化(Java 9+)

private static final Map MY_MAP = Map.of(1, "one", 2, "two");

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