Java tutorial
//package com.java2s; import android.content.Context; import android.os.Environment; import android.os.StatFs; import android.text.format.Formatter; import java.io.File; public class Main { public static String getAvailableExternalMemorySize(Context context) { if (externalMemoryAvailable()) { File path = Environment.getExternalStorageDirectory(); StatFs stat = new StatFs(path.getPath()); long blockSize = stat.getBlockSize(); long availableBlocks = stat.getAvailableBlocks(); return Formatter.formatFileSize(context, availableBlocks * blockSize); } else { return "ERROR"; } } public static boolean externalMemoryAvailable() { return Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED); } }