How to create a file extension association with the program in Windows

Assume that you have a program named "table-explorer.exe".
And you want to open all ".csv" and ".sas7bdat" files using  this program by default in Windows.

First you need to create a file extension association with the program via these commands:

reg add HKCU\SOFTWARE\Classes\.csv /d "table-explorer" /f
reg add HKCU\SOFTWARE\Classes\.sas7bdat /d "table-explorer" /f


And then register the application:

reg add HKCU\SOFTWARE\Classes\table-explorer\shell\open\command /d "\"C:\Path\to\table-explorer.exe\"" /f

How to bind hotkeys in Java FX

It is possible to create global keyboard shortcuts using a code like this:

import static javafx.scene.input.KeyCombination.keyCombination;
...
private void initHotkeys() {
    ObservableMap accelerators = stage.getScene().getAccelerators();
    accelerators.put(keyCombination("Alt+S"), searchTextField::requestFocus);
    accelerators.put(keyCombination("Alt+C"), columnsTextField::requestFocus);
    accelerators.put(keyCombination("Alt+O"), openFileButton::fire);
    accelerators.put(keyCombination("Alt+E"), exportButton::fire);
    accelerators.put(keyCombination("Alt+T"), truncateButton::fire);
    accelerators.put(keyCombination("Alt+H"), () -> filterChoiceBox.setValue(MATCH_HIGHLIGHT));
    accelerators.put(keyCombination("Alt+F"), () -> filterChoiceBox.setValue(MATCH_FILTER));
    accelerators.put(keyCombination("Alt+U"), () -> filterChoiceBox.setValue(MATCH_FILTER_UNIQUE));
    accelerators.put(keyCombination("Alt+D"), () -> {
        //todo some debug action
    });
}

How much memory is allocated to the String object in Java

	Size in bytes
String() object
Object header	16
Hash field	4
Reference to char array	4
Char[] array
Object header	16
Array length	4
Array size	N*2

String allocates in memory at least (24+20+N*2) bytes, where N - number of characters in the string. If N=10 then string size = 64 bytes.

One million of these strings = 64 000 000 bytes. But also we need array or collection to store these strings.
This requires additional memory.
ArrayList<String>(1 000 000) ~= 4 000 000 bytes (4 bytes per reference to string object).

So, total size will be 68 000 000 bytes.

Gist code: Output:

3,355,792 Initial
1,217,624 After GC
218,921,768 Created list of strings
76,489,936 After GC
68,000,000 Expected size in memory

But if you have many similar strings, then using of String.intern() greatly reduces amount of allocated memory. Output:

3,355,792 Initial
1,217,792 After GC
106,750,232 Created list of strings
13,127,480 After GC
68,000,000 Expected size in memory

10x less memory! 6.8 megabytes instead of 68

The best resolutions

List of multiple resolutions in the most popular proportions:

Base width	1/2	2/3	3/4	4/5	5/6	9/16	10/16
240	120	160	180	192	200	135	150
480	240	320	360	384	400	270	300
720	360	480	540	576	600	405	450
960	480	640	720	768	800	540	600
1200	600	800	900	960	1000	675	750
1440	720	960	1080	1152	1200	810	900
1680	840	1120	1260	1344	1400	945	1050
1920	960	1280	1440	1536	1600	1080	1200
2160	1080	1440	1620	1728	1800	1215	1350
2400	1200	1600	1800	1920	2000	1350	1500
2640	1320	1760	1980	2112	2200	1485	1650
2880	1440	1920	2160	2304	2400	1620	1800
3120	1560	2080	2340	2496	2600	1755	1950
3360	1680	2240	2520	2688	2800	1890	2100
3600	1800	2400	2700	2880	3000	2025	2250
3840	1920	2560	2880	3072	3200	2160	2400

Read SAS file in Java

Some companies (banks, medical and pharmaceutical companies) store their data in the SAS (.sas7bdat) format. This is old, legacy, but still actual format for tabular data. And this format is proprietary and fiddly.

But what if you have to work with the data from the sas-file? For me, solution is pretty simple - convert the data from the sas-file to some convenient and popular format. For example, to the MongoDB. And then access this data via nice query-like API.

In my new mini-project sas2mongo I show how to convert data from the sas-file into the MongoDB in Java.