ChMapDemoAdvanced.java

package com.test;

import net.openhft.chronicle.map.ChronicleMap;
import net.openhft.chronicle.map.ChronicleMapBuilder;
import net.openhft.lang.model.DataValueClasses;
import net.openhft.lang.values.LongValue;

import java.io.File;
import java.io.IOException;


public class ChMapDemoAdvanced {
    public void demoOffHeapReference() throws IOException {
        //Build the map: Not the actual interface which is a ConcurrentMap
        ChronicleMap<String, LongValue> demoMap =
                ChronicleMapBuilder.of(String.class, LongValue.class)
                        .entries(10_000) //the maximum number of entries for the map
                        .averageKeySize(32) //the average number of bytes for the key
                        .createPersistedTo(new File("/tmp/demodir", "demomap1"));
        
        //The LongValue is direct value backed by off heap memory
        LongValue userRequests = DataValueClasses.newDirectInstance(LongValue.class);
        //Get the number of requests associated with "users1" using the variable 'userRequest'.
        //Note the zero garbage technique
        demoMap.acquireUsing("user1", userRequests);

        //increment the number requests which is automatically saved to disk
        userRequests.addValue(1);

        System.out.println("user1 has made " + userRequests.getValue() + " requests.");
    }


    public static void main(String[] args) throws IOException {
        ChMapDemoAdvanced chMapDemo = new ChMapDemoAdvanced();
        chMapDemo.demoOffHeapReference();
    }
}