Android: write string to a file

FileOutputStream os = new FileOutputStream(fileName);

OutputStreamWriter osw = new OutputStreamWriter(os); 

osw.write(str);

osw.flush();

osw.close();

Do not use

DataOutputStream os = new DataOutputStream(new FileOutputStream(file));

os.writeUTF(str); // this will write a weird char at the beginning of the file

os.writeUTF writes the string with a modified UTF-8 encoding. If the file is opened by WebView as HTML, a weird char shows up at the beginning of the file. 

Android: run time-consuming work in another thread

Many times you want to run time-consuming work in another thread instead of main thread because UI will stop response if you run it in main thread, and the user will frustrate.

It is easy to implement:

Just wrap up the time-consuming code with

new Thread(new Runnable() {

  public void run() {

  //... time-consuming work

  }

}).start();

Java: inline initializer for Map

Flurry has a function

FlurryAgent.logEvent(String event, Map<String,String> parameters)

It can be called with an inline initializer like this

FlurryAgent.logEvent("event", new HashMap<String,String>() {{
  put("key1","val1");
  put("key2","val2");
}});

Timing in Java

Timing in Java is easy.

long start = System.nanoTime();

long time = System.nanoTime()-start;

The unit is nanosecond. The long type is enough for 300 years.