Map的快速构建

想要快速创建Map，不用频繁new，最快的方法就是用Guava，使用ImmutableMap.of("a", 1, "b", 2, "c", 3);

Guava

Map<String, Integer> left = ImmutableMap.of("a", 1, "b", 2, "c", 3);

java 9

Map<Integer, String> map = Map.of(1, "A", 2, "B", 3, "C");

超过 10 组会不支持，那么就要这样：

Map.ofEntries(
    Map.entry( 1, false ),
    Map.entry( 2, true ),
    Map.entry( 3, false ),
    Map.entry( 4, true ),
    Map.entry( 5, false ),
    Map.entry( 6, true ),
    Map.entry( 7, false ),
    Map.entry( 8, true ),
    Map.entry( 9, false ),
    Map.entry( 10, true ),
    Map.entry( 11, false )
);

匿名内部类

Map mymap = new HashMap() {
    {
        put(1, "one");
        put(2, "two");
    }
};

Collections.unmodifiableMap(new HashMap() {
{
    put(0, "zero");
    put(1, "one");
    put(2, "two");
    put(3, "three");
    put(4, "four");
    put(5, "five");
    put(6, "six");
    put(7, "seven");
    put(8, "eight");
    put(9, "nine");
    put(10, "ten");
    put(11, "eleven");
    put(12, "twelve");
}
});

"你们还在用new吗?"

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