public AwsSecurityFinding addUserDefinedFieldsEntry(String key, String value) {
        if (null == this.userDefinedFields) {
            this.userDefinedFields = new java.util.HashMap<String, String>();
        }
        if (this.userDefinedFields.containsKey(key))
            throw new IllegalArgumentException("Duplicated keys (" + key.toString() + ") are provided.");
        this.userDefinedFields.put(key, value);
        return this;
    }
Add a single UserDefinedFields entry

@see AwsSecurityFinding#withUserDefinedFields
@returns a reference to this object so that method calls can be chained together.
aws-java-sdk-securityhub/src/main/java/com/amazonaws/services/securityhub/model/AwsSecurityFinding.java