Java – Google common cache – the default value of maximumsize (and other “optional” settings) – you want a cache that uses all “available” memory

I just found guava through the search cache API (it's perfect for my needs)

In my opinion, a good default value for maximumsize is relative to runtime getRuntime(). freeMemory();

Finally, I want a cache that uses the memory available on a given system So I need an eviction policy to ask how much freememory () is available (possibly related to runtime. Getruntime()) maxMemory())

Solution

I asked me to question the same thing. I couldn't find anything on the Internet So I did this very primitive test

import com.google.common.cache.Cache;
import com.google.common.cache.CacheBuilder;

import java.util.concurrent.TimeUnit;

public class CacheTest {
    public static void main(String[] args) {
        Cache<String,String> cache = CacheBuilder.newBuilder().build();
        int counter = 0;
        while(true){
            cache.put("key"+counter++,"value");
            System.out.println("size:"+cache.size());
        }
    }
}

As can be seen from the figure below, the memory usage increases to the maximum available space and becomes constant I waited for a few minutes and there was no outofmemoryerror What happens is that after a few seconds, a new entry is added to the map, so errors may occur in the future

Conclusion: you do not have to set the maximumsize value, but I recommend that you use some eviction policy (expireafteraccess or expireafterwrite) to clean up the cache and avoid outofmemoryerror And avoid reducing cache performance