Java – How to differentiate between time to live and time to idle in ehcache

ehcachejava

The docs on ehache says:

timeToIdleSeconds: Sets the time to idle for an element before it expires.
i.e. The maximum amount of time between accesses before an element expires

timeToLiveSeconds: Sets the time to live for an element before it expires.
i.e. The maximum time between creation time and when an element expires.

I understand timeToIdleSeconds

But does it means that after the creation & first access of a cache item, the timeToLiveSeconds is not applicable anymore ?

Best Answer

timeToIdleSeconds enables cached object to be kept in as long as it is requested in periods shorter than timeToIdleSeconds. timeToLiveSeconds will make the cached object be invalidated after that many seconds regardless of how many times or when it was requested.

Let's say that timeToIdleSeconds = 3. Then the object will be invalidated if it hasn't been requested for 4 seconds.

If timeToLiveSeconds = 90, then the object will be removed from cache after 90 seconds, even if it has been requested few milliseconds in the 90th second of its short life.

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Java – What are the differences between a HashMap and a Hashtable in Java

There are several differences between HashMap and Hashtable in Java:

Hashtable is synchronized, whereas HashMap is not. This makes HashMap better for non-threaded applications, as unsynchronized Objects typically perform better than synchronized ones.
Hashtable does not allow null keys or values. HashMap allows one null key and any number of null values.
One of HashMap's subclasses is LinkedHashMap, so in the event that you'd want predictable iteration order (which is insertion order by default), you could easily swap out the HashMap for a LinkedHashMap. This wouldn't be as easy if you were using Hashtable.

Since synchronization is not an issue for you, I'd recommend HashMap. If synchronization becomes an issue, you may also look at ConcurrentHashMap.

Java – the difference between public, protected, package-private and private in Java

The official tutorial may be of some use to you.

	Class	Package	Subclass (same pkg)	Subclass (diff pkg)	World
`public`	+	+	+	+	+
`protected`	+	+	+	+
no modifier	+	+	+
`private`	+

+ : accessible
blank : not accessible

Best Answer

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Java – What are the differences between a HashMap and a Hashtable in Java

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