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

@see Put#withExpressionAttributeValues
@returns a reference to this object so that method calls can be chained together.
aws-java-sdk-dynamodb/src/main/java/com/amazonaws/services/dynamodbv2/model/Put.java