I have a java application that uses mysql as back end, every开发者_Python百科 night we take a backup of mysql using mysqldump and application stops working for that time period(app 20 min).
Suppose I have a Java method that 开发者_高级运维returns a HashMapobject. Because a LinkedHashMap is a subclass of HashMap, I can return a LinkedHashMap from this method just fine.
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