Android Java 8 Stream API Example

Demo app of using Java 8 features with Retrolambda and Lightweight-Stream-API.

Features:

• () -> lambda expression

  findViewById(R.id.go).setOnClickListener(v -> {
  finalintindex = mActionSpinner.getSelectedItemPosition();
  if (index != Spinner.INVALID_POSITION) {
  action(actions[index]);
  }
  });

• Method::references

  intcmp = Objects.compare(word, other.word, String::compareToIgnoreCase);

• Stream.API()

  returnStream.of(lines)
  .map(str -> str.split("\t"))
  .filter(arr -> arr.length == 2)
  .map(arr -> newWord(arr[0], arr[1]))
  .collect(Collectors.toList());

• switch for "string"

  switch (action) {
  case"filter 1":
  // Filter one wordstream = stream.filter(p -> p.getWord().split(" ").length == 1);
  break;
  case"filter 2+":
  // Filter two and more wordsstream = stream.filter(p -> p.getWord().split(" ").length >= 2);
  break;
  // ...
  }

• try(with-resources) {}

  finalList<String> lines = newArrayList<>();
  try (finalInputStreamis = context.getAssets().open("words.txt");
  finalInputStreamReaderisr = newInputStreamReader(is, "UTF-8");
  finalBufferedReaderreader = newBufferedReader(isr)) {
  Stringline;
  while ( (line = reader.readLine()) != null ) {
  lines.add(line);
  }
  }

• Objects (from Java 7)

  @Overridepublicbooleanequals(Objecto) {
  // ...finalWordother = (Word) o;
  returnObjects.equals(translate, other.translate) &&
  Objects.equals(word, other.word);
  }
  @OverridepublicinthashCode() {
  returnObjects.hash(word, translate);
  }

• try {Exceptional} catch (functional try/catch)

  returnExceptional.of(() -> {
  finalInputStreamis = context.getAssets().open("words.txt");
  // ... operations which throws Exception ...returnlines;
  }).ifException(e -> Log.e("Java 8 Example", "Utils.readWords", e))
  .getOrElse(newArrayList<>());

Links

Demo app: Java8StreamExample.apk

Blog (Russian): Java 8 в Android со Stream API и лямбдами

Retrolambda: https://github.com/orfjackal/retrolambda

Lightweight-Stream-API: https://github.com/aNNiMON/Lightweight-Stream-API

Screenshots