在Java8里创建Stream的几种方法

import java.math.BigInteger;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.regex.Pattern;
import java.util.stream.Stream;
 
/**
 *
 * @author Kangjun Ways of Creating a Stream in Java 8
 */
public class StreamDemo {
 
    public static void main(String[] args) {
 
        arraysStream();
 
        collectionStream();
 
        generate();
 
        iterateStream();
         
        populaStream();
    }
 
    //From Arrays
    public static void arraysStream() {
        String[] arr = {"program","creek","program","java","web","program"};
        Stream<String> stream = Stream.of(arr);
        System.out.println(Arrays.toString(arr));
 
    }
 
    //From Collections
    public static void collectionStream() {
        List<String> list = new ArrayList<>();
        list.add("Java");
        list.add("python");
        list.add("c++");
        list.add("c");
        list.add("lisp");
 
        Stream<String> stream = list.stream().filter(p -> p.length() > 3);
        String[] arr = stream.toArray(String[]::new);
        System.out.println(Arrays.toString(arr));
    }
 
    //Use Stream.generate()
    public static void generate() {
        Stream<String> stream = Stream.generate(() -> "test").limit(10);
        String[] strArr = stream.toArray(String[]::new);
        System.out.println(Arrays.toString(strArr));
    }
 
    //Use Stream.iterate()
    public static void iterateStream() {
        Stream<BigInteger> bigIntStream = Stream.iterate(BigInteger.ZERO,n -> n.add(BigInteger.TEN)).limit(10);
        BigInteger[] bigIntArr = bigIntStream.toArray(BigInteger[]::new);
        System.out.println(Arrays.toString(bigIntArr));
    }
 
    // From Popular APIs
    public static void populaStream() {
        String sentence = "Program creek is a Java site.";
        Stream<String> wordStream = Pattern.compile("W").splitAsStream(sentence);
        String[] wordArr = wordStream.toArray(String[]::new);
        System.out.println(Arrays.toString(wordArr));
    }
}