Java8 Stream API (Create stream)

You've learned that by Java8 the new stream method in the Collection interface, you can convert any collection into a stream. If you are dealing with an array , you can also convert it to a stream using the static Stream.of method :

Package Java8test;import Java.util.stream.stream;public class T6 {public static void main (string[] args) {//Use        The static method of Stream of stream<string> words = Stream.of ("Ab,cd,ef,gh". Split (","));    System.out.printf ("num:%d", Words.count ()); }}

The of method accepts variable-length arguments, so you can construct a stream that contains any parameter :

Package Java8test;import Java.util.stream.stream;public class T6 {public static void main (string[] args) {//Use        The static method of the Stream, the parameter is any number of arguments stream<string> words = Stream.of ("Gently", "Down", "the", "Stream");    System.out.printf ("num:%d", Words.count ()); }}

Use the arrays.stream (array,from,to) method to convert part of an array to stream. Example:

Package Java8test;import Java.util.arrays;import Java.util.stream.stream;public class T6 {public static void main (Stri        Ng[] (args) {string[] arr = {"11", "22", "33", "44", "55"};        Note here stream<string> words = Arrays.stream (arr,1,3);    System.out.printf ("first:%s", Words.findfirst (). get ()); }}

To create a Stream that does not contain any elements, you can use the static Stream.empty method:

Package Java8test;import Java.util.stream.stream;public class T6 {public static void main (string[] args) {//Example         Generics <String> will be deduced by the compiler, which is the same as Stream.<string>empty () stream<string> silence = Stream.empty ();    System.out.println (Silence.count ()); }}

The stream interface has two static methods to create an infinite stream . The generate method takes a parameterless function (or, technically, an object of the Supplier<t> interface). When you need a stream value, you can call the method to produce a value. You can create a stream that contains a constant value by using the following code:

Package Java8test;import Java.util.stream.stream;public class T6 {public static void main (string[] args) {//Example        , use the Generate () method to produce a value stream<string> Echos = Stream.generate ((), "Echo");    System.out.println (Echos.findfirst (). get ()); }}

Or a stream containing random numbers :

Package Java8test;import Java.util.stream.stream;public class T6 {public static void main (string[] args) {//Example        , use the Generate () method to produce a random number stream<double> Echos = Stream.generate (Math::random);    System.out.println (Echos.findfirst (). get ()); }}

To create a shape like 0 1 2 3 4 .... For an infinite sequence , you can use the iterate method. It takes a seed (seed) value and a function (technically, an object of the Unaryoperator<t> interface) as a parameter, and the function is applied repeatedly to the previous value. For example:

example, use the iterator method to produce an infinite sequence stream<biginteger> integers = stream.iterate (Biginteger.zero, N-N.add ( Biginteger.one));

The first element in the sequence is the seed Biginteger.zero, the second value is F (seed), or 1, the next element is F (f (seed)), or 2, and so on.

Note: In Java8, a number of methods are added to generate the stream. For example, thePattern class adds a Splitasstream method that separates Charsequence objects according to regular expressions. You can use the following code to separate a string by the word.

The static method Files.lines Returns a stream containing all the rows in the file. The stream interface has a parent interface autocloseable. When the close method is raised on a stream, the underlying file is also closed. To ensure that the file is closed, it is best to use the Try-with-resources statement provided in Java7, as follows:

Try (stream<string> lines = files.lines (path)) {//Some processing of lines}

This way, when you exit the TRY statement block normally or throw an exception, the underlying file associated with the stream is closed.

Java8 Stream API (Create stream)