在Java8里創建Stream的幾種方法

創建Stream的方法共有5種，分別為如下

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", "creek", "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));

}
}</pre>