runtime

A Java method to log Android memory use

As a quick note today, here’s a little Java method that I use to log Android memory use (RAM use) from an Activity or Fragment:

private void logMemoryInfo(Context context, String TAG) {
   ActivityManager activityManager = (ActivityManager) context.getSystemService(getActivity().ACTIVITY_SERVICE);
   int memoryClass = activityManager.getMemoryClass();
   ActivityManager.MemoryInfo memoryInfo = new ActivityManager.MemoryInfo();
   activityManager.getMemoryInfo(memoryInfo);

   Log.i(TAG, "\n------------ RAM -------------");
   Log.i(TAG, "mem class: " + memoryClass);
   Log.i(TAG, "mem avail: " + memoryInfo.availMem);
   Log.i(TAG, "low mem:   " + memoryInfo.lowMemory);
   Log.i(TAG, "threshold: " + memoryInfo.threshold);

   long mb = 1024*1024;
   Runtime runtime = Runtime.getRuntime();
   Log.i(TAG, "Used Memory:  " + (runtime.totalMemory() - runtime.freeMemory()) / mb);
   Log.i(TAG, "Free Memory:  " + runtime.freeMemory()  / mb);
   Log.i(TAG, "Total Memory: " + runtime.totalMemory() / mb);
   Log.i(TAG, "Max Memory:   " + runtime.maxMemory()   / mb);
}

Running system commands in Java applications

UPDATE: This article has been replaced by my newer "Java exec with ProcessBuilder and Process" article. While the Java code shown in this tutorial works on simple "Java exec" cases, the new article shows how to properly read the output streams from your system command in Java threads, and also how to write to your command's standard input, if necessary.

Feel free to read this article for background/legacy information, but I strongly recommend that you use the source code I'm sharing in my newer "Java exec" article, because it resolves the standard input, output, and error problems that I didn't handle properly in the code below.

Introduction

I've read a lot about Java but one of the things I rarely see discussed is how you should go about running external system commands. Of course, you probably don't read much about this because it takes away from the portability of Java applications. For instance, if you write a Java application on a Unix system, you might be interested in running the "ps -ef" command, and reading the output of the command. For Unix systems this is great, but unfortunately, this same program won't work on a Windows system because the ps command isn't available on Windows.