streamtests

gistfile1.txt

package org.pierre.streams;


import org.junit.jupiter.api.Test;

import java.io.BufferedReader;
import java.io.FileReader;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
import java.util.stream.Stream;

public class StreamTest {

    /**
     * https://docs.oracle.com/javase/8/docs/api/java/util/stream/package-summary.html#StreamOps
     */
    @Test
    public void obtainStream() {
        // From a Collection via the stream() and parallelStream() methods;
        List<String> myStrings = List.of("a", "b", "c");
        Stream<String> myStream1 = myStrings.stream();

        // From an array via Arrays.stream(Object[]);
        String[] myStringsArray = myStrings.toArray(new String[0]);
        Stream<String> myStream2 = Arrays.stream(myStringsArray);

        // From static factory methods on the stream classes, such as Stream.of(Object[]), IntStream.range(int, int)
        // or Stream.iterate(Object, UnaryOperator);
        Stream<String> myStream3 = Stream.of("a", "b", "c");
        IntStream myStream4 = IntStream.of(1, 2, 3);
        Stream<Integer> myStream5 = Stream.iterate(1, integer -> integer++);

        // using Builder
        IntStream myStream6 = IntStream.builder().add(1).add(2).add(3).build();

        // Read file content From BufferedReader
        try (BufferedReader br = new BufferedReader(new FileReader("listofwords.txt"))) {
            Stream myStream7 = br.lines();
        }
        catch (Exception e) {
            e.printStackTrace();
        }

        // Read file content from Files and Paths
        Path path = Paths.get("listofwords.txt");
        try (Stream<String> lines = Files.lines(path)) {
        }
        catch (Exception e) {
            e.printStackTrace();
        }

        // you can directly manipulate a Stream with an iterator
        Iterator<Integer> iterator = myStream6.iterator();

        // you can change the list BEFORE you consume the stream, and change is reflected in Stream
        List<String> l = new ArrayList(Arrays.asList("one", "two"));
        Stream<String> sl = l.stream();
        l.add("three");
        String s = sl.collect(Collectors.joining(" "));



    }
}