java - 如何在 Java 8 中组合两个 ImmutableMap<String,String>？

Question

我试过这个代码:

    final ImmutableMap<String, String> map1 = ImmutableMap.of("username", userName, "email", email1, "A", "A1",
            "l", "500L");
    final ImmutableMap<String, String> map2 = ImmutableMap.of("b", "ture", "hashed_passwords", "12345", "e",
            "TWO", "fakeProp", "fakeVal");

    final ImmutableMap<String, String> map3 = ImmutableMap.builder().putAll(map1).putAll(map2).build();

但出现错误:

Error:(109, 105) java: incompatible types: com.google.common.collect.ImmutableMap<java.lang.Object,java.lang.Object> cannot be converted to com.google.common.collect.ImmutableMap<java.lang.String,java.lang.String>

否则我怎么能投呢？

Answer 1

Java 类型推断并不总是像我们希望的那样好。有时，您需要提供类型提示才能解决问题。
在您的情况下，您需要为 ImmutableMap 构建器方法提供显式泛型类型。

ImmutableMap.<String, String>builder()
    .putAll(map1)
    .putAll(map2)
    .build();