liquibase-core/src/main/java/liquibase/util/SmartMap.java
public <T> T get(String key, T defaultValue) {
        Class type;
        if (defaultValue == null) {
            type = Object.class;
        } else {
            type = defaultValue.getClass();
        }
        Object value = get(key, type);

        if (value == null) {
            return defaultValue;
        }
        return (T) value;
    }
public <T> T get(String key, T defaultValue) {
        Class type;
        if (defaultValue == null) {
            type = Object.class;
        } else {
            type = defaultValue.getClass();
        }
        Object value = get(key, type);

        if (value == null) {
            return defaultValue;
        }
        return (T) value;
    }
Return the value for the given key converted to the type of the default value.
If the value is null, defaultValue is returned.
Conversion is done using {@link #get(String, Class)}