stokito/MemoryEater.java

## README.md

      
    Raw
  

              README.md
            
          
    https://www.google.com.ua/search?q=java+recover+out+of+memory&oq=java+recover+out+of+memory
https://venishjoe.net/post/recover-from-out-of-memory-errors-in-java/
https://github.com/apache/derby/blob/f16c46cbdd5be8dd9bdcee935ec1f68970146478/java/org.apache.derby.engine/org/apache/derby/iapi/services/memory/LowMemory.java
https://stackoverflow.com/questions/2679330/catching-java-lang-outofmemoryerror
-XX:MaxHeapFreeRatio=10
-XX:MinHeapFreeRatio=10
which pretty much means that if after gc, more than 10% of the heap is free, it will try to give the memory back to the OS. and it will grow the heap only if more than 90% of the heap is used after gc.
this might slow down your program, because the gc will be constantly changing allocated memory size. and it is possible that it will have no effect at all if your program allocates large amount of memory in a short period of time.
https://confluence.atlassian.com/confkb/how-to-fix-out-of-memory-errors-by-increasing-available-memory-154071.html
https://stackify.com/best-practices-exceptions-java/
https://10kloc.wordpress.com/2013/03/09/runtimeexceptions-try-catch-or-not-to-catch/
https://www.javamex.com/tutorials/exceptions/exceptions_uncaught_handler.shtml
https://techblug.wordpress.com/2011/07/16/detecting-low-memory-in-java/
https://habr.com/post/253683/
https://plumbr.io/outofmemoryerror/java-heap-space
http://www.vogella.com/tutorials/JavaPerformance/article.html

  
## MemoryEater.java
package name.stokito.memeater;

import org.apache.derby.iapi.services.memory.LowMemory;

import java.lang.Thread.UncaughtExceptionHandler;
import java.util.ArrayList;
import java.util.List;

public class MemoryEater {
    private static final int MB = 1048576;
    private static List leakHolder = new ArrayList();
    private static UncaughtExceptionHandler oomRestorer = new OomRestorer();
    private static LowMemory lowMemory = new LowMemory();

    public static void main(String[] args) throws InterruptedException {
        Thread.setDefaultUncaughtExceptionHandler(oomRestorer);
        long maxMemory = Runtime.getRuntime().maxMemory();
        System.out.println("Max JVM memory: " + maxMemory);
        System.out.println("Total JVM memory: " + Runtime.getRuntime().totalMemory());
        int i;
        for (i = 1; ; i++) {
            if (lowMemory.isLowMemory()) {
                System.out.println("Too low memory, skipping");
                i--;
                Thread.sleep(500);
                continue;
            }
            try {
                byte b[] = new byte[MB];
                leakHolder.add(b);
                Runtime rt = Runtime.getRuntime();
                long freeMemory = rt.freeMemory();
                long consumed = Runtime.getRuntime().totalMemory() - freeMemory;
                System.out.println("Allocated: " + i + "mb, consumed: " + consumed + " bytes, free memory: " + freeMemory + " bytes i.e. " + (freeMemory / 1024.0 / 1024.0) + "mb");
                Thread.sleep(500);
            } catch (OutOfMemoryError oom) {
                System.out.println("Catching out of memory error");
                leakHolder = null;
                lowMemory.setLowMemory();
                System.out.println("Memory freed, available: " + Runtime.getRuntime().freeMemory());
                leakHolder = new ArrayList();
                i = 0;
            }
        }
    }

    public static class OomRestorer implements UncaughtExceptionHandler {
        @Override
        public void uncaughtException(Thread thread, Throwable throwable) {
            System.out.println("Ololo " + throwable.toString());
            leakHolder = null;
            System.gc();
        }
    }

}
	package name.stokito.memeater;

	import org.apache.derby.iapi.services.memory.LowMemory;

	import java.lang.Thread.UncaughtExceptionHandler;
	import java.util.ArrayList;
	import java.util.List;

	public class MemoryEater {
	private static final int MB = 1048576;
	private static List leakHolder = new ArrayList();
	private static UncaughtExceptionHandler oomRestorer = new OomRestorer();
	private static LowMemory lowMemory = new LowMemory();

	public static void main(String[] args) throws InterruptedException {
	Thread.setDefaultUncaughtExceptionHandler(oomRestorer);
	long maxMemory = Runtime.getRuntime().maxMemory();
	System.out.println("Max JVM memory: " + maxMemory);
	System.out.println("Total JVM memory: " + Runtime.getRuntime().totalMemory());
	int i;
	for (i = 1; ; i++) {
	if (lowMemory.isLowMemory()) {
	System.out.println("Too low memory, skipping");
	i--;
	Thread.sleep(500);
	continue;
	}
	try {
	byte b[] = new byte[MB];
	leakHolder.add(b);
	Runtime rt = Runtime.getRuntime();
	long freeMemory = rt.freeMemory();
	long consumed = Runtime.getRuntime().totalMemory() - freeMemory;
	System.out.println("Allocated: " + i + "mb, consumed: " + consumed + " bytes, free memory: " + freeMemory + " bytes i.e. " + (freeMemory / 1024.0 / 1024.0) + "mb");
	Thread.sleep(500);
	} catch (OutOfMemoryError oom) {
	System.out.println("Catching out of memory error");
	leakHolder = null;
	lowMemory.setLowMemory();
	System.out.println("Memory freed, available: " + Runtime.getRuntime().freeMemory());
	leakHolder = new ArrayList();
	i = 0;
	}
	}
	}

	public static class OomRestorer implements UncaughtExceptionHandler {
	@Override
	public void uncaughtException(Thread thread, Throwable throwable) {
	System.out.println("Ololo " + throwable.toString());
	leakHolder = null;
	System.gc();
	}
	}

	}