#590 add explanation for Visitor
#590 add explanation for Visitor

javaseeds/java-design-patterns,mookkiah/java-design-patterns,javaseeds/java-design-patterns,javaseeds/java-design-patterns,mookkiah/java-design-patterns,javaseeds/java-design-patterns,mookkiah/java-design-patterns,mookkiah/java-design-patterns