bson/src/main/org/bson/BsonDocument.java
public BsonInt32 getInt32(final Object key, final BsonInt32 defaultValue) {
        if (!containsKey(key)) {
            return defaultValue;
        }
        return get(key).asInt32();
    }
public BsonInt32 getInt32(final Object key, final BsonInt32 defaultValue) {
        if (!containsKey(key)) {
            return defaultValue;
        }
        return get(key).asInt32();
    }
If the document does not contain the given key, return the given default value.  Otherwise, gets the value of the key as a
BsonInt32.

@param key the key
@param defaultValue the default value
@return the value of the key as a BsonInt32
@throws org.bson.BsonInvalidOperationException if the document contains the key but the value is not of the expected type