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

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