Multiple entries with same key

Java异常模拟代码如下：

public static void main(String[] args) {
    new HashMap<String, String>(){{
        put("1", "1");
        put("1", "1");
    }};
    ImmutableMap.<String, String>builder()
            .put("1", "1")
            .put("1", "1")
            .build();
}

异常信息如下:

Exception in thread "main" java.lang.IllegalArgumentException: Multiple entries with same key: 1=1 and 1=1
    at com.google.common.collect.ImmutableMap.conflictException(ImmutableMap.java:214)
    at com.google.common.collect.ImmutableMap.checkNoConflict(ImmutableMap.java:208)
    at com.google.common.collect.RegularImmutableMap.checkNoConflictInKeyBucket(RegularImmutableMap.java:146)
    at com.google.common.collect.RegularImmutableMap.fromEntryArray(RegularImmutableMap.java:109)
    at com.google.common.collect.ImmutableMap$Builder.build(ImmutableMap.java:392)
    at com.gome.tccb.domain.job.ModelPlanningWorkflowStarter.main(ModelPlanningWorkflowStarter.java:415)

原因是ImmutableMap是不可变Map，如果已经设置了一个特定的key1，则不能再次设置覆盖key1，内部实现会检查抛异常。