在Java8中，建立Stream的五種方式

Java8 已然到來，最大的變動就是Lambda. lambda中的stream是處理集合的源頭，下面簡單介紹一下建立stream的五種方式

一、經過數組建立

String[] arr = { "Java", "lambda", "test", "stream", "java", "web",
		"program" };
stream = Stream.of(arr);

stream = Stream.of("Java", "lambda", "test", "stream", "java",
		"web", "program");

String[] stringArr = {"a", "b", "c", "d"};
Stream<String> stream = Arrays.stream(stringArr);

二、經過集合來建立

// from collection
List<String> list = new ArrayList<String>();
list.add("java");
list.add("php");
list.add("python");
stream = list.stream();

三、經過generate方法來建立

Stream<String> stream = Stream.generate(() -> "test").limit(10);
String[] strArr = stream.toArray(String[]::new);
System.out.println(Arrays.toString(strArr));

四、經過iterate方法來建立

Stream<BigInteger> bigIntStream = Stream.iterate(BigInteger.ZERO, n -> n.add(BigInteger.ONE)).limit(10);
BigInteger[] bigIntArr = bigIntStream.toArray(BigInteger[]::new);
System.out.println(Arrays.toString(bigIntArr));

五、經過流行的API

String sentence = "Lambda  is a coming now.";
Stream<String> wordStream = Pattern.compile("\\W").splitAsStream(sentence);
String[] wordArr = wordStream.toArray(String[]::new);
System.out.println(Arrays.toString(wordArr));

以上五種方式用來建立你的stream，functional 時代已然到來，擁抱lambda吧，java coder...