UsedMemoryMonitor.java

UsedMemoryMonitor.java

package org.dhatim.fastexcel;

import java.util.concurrent.CompletableFuture;

import static java.lang.String.format;

public class UsedMemoryMonitor<E extends Exception> {

    volatile boolean stop = false;
    volatile long maxUsedMemoryMB = 0;

    public static <E extends Exception> long getMaxMemoryUsedDuring(VoidCallable<E> callable) throws E {
        UsedMemoryMonitor monitor = new UsedMemoryMonitor();
        callable.call();
        monitor.stop = true;
        return monitor.maxUsedMemoryMB;
    }

    private UsedMemoryMonitor() {
        CompletableFuture.runAsync(() -> {
            long initial = getRuntimeUsedMemoryMB();
            while (!stop) {
                long used = getRuntimeUsedMemoryMB() - initial;
                if(used > maxUsedMemoryMB){
                    maxUsedMemoryMB = used;
                    System.out.println(format("max memory used %s MB", maxUsedMemoryMB));
                }
                sleep(100);
            }
        });
    }

    private static void sleep(int millis) {
        try {
            Thread.sleep(millis);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        }
    }

    private static long getRuntimeUsedMemoryMB() {
        final long MEGABYTE = 1024L * 1024L;
        Runtime runtime = Runtime.getRuntime();
        runtime.gc();
        return (runtime.totalMemory() - runtime.freeMemory()) / MEGABYTE;
    }

    @FunctionalInterface
    interface VoidCallable<E extends Exception> {
        void call() throws E;
    }
}