Directly Initialize a HashMap in Java

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The following code snippet in Java 9+ initialize an immutable HashMap with up to 10 elements.

import java.util.Map;

Map<String, String> m1 = Map.of(
    "a", "b",
    "c", "d"
);

System.out.println(m1);

{c=d, a=b}

The following code snippet in Java 9+ initialize an immutable HashMap with arbitrary number of elements.

import java.util.Map;
import static java.util.Map.entry;    
Map<String, String> m2 = Map.ofEntries(
    entry("a", "b"),
    entry("c", "d")
);

System.out.println(m2);

{c=d, a=b}

References¶