public Job addUserMetadataEntry(String key, String value) {
        if (null == this.userMetadata) {
            this.userMetadata = new com.amazonaws.internal.SdkInternalMap<String, String>();
        }
        if (this.userMetadata.containsKey(key))
            throw new IllegalArgumentException("Duplicated keys (" + key.toString() + ") are provided.");
        this.userMetadata.put(key, value);
        return this;
    }
Add a single UserMetadata entry

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