package solutions;
import java.io.BufferedReader;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
import org.junit.After;
import org.junit.Before;
import org.junit.Ignore;
import org.junit.Test;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertTrue;
/**
* This set of exercises covers simple stream pipelines,
* including intermediate operations and basic collectors.
*
* Some of these exercises use a BufferedReader variable
* named "reader" that the test has set up for you.
*/
public class D_SimpleStreams {
/**
* Given a list of words, create an output list that contains
* only the odd-length words, converted to upper case.
*/
@Test
public void ex06_upcaseOddLengthWords() {
List<String> input = Arrays.asList(
"alfa", "bravo", "charlie", "delta", "echo", "foxtrot");
//TODO//List<String> result = null;
//BEGINREMOVE
List<String> result =
input.stream()
.filter(w -> (w.length() & 1) == 1)
.map(String::toUpperCase)
.collect(Collectors.toList());
// Alternatives:
// Instead of w -> (w.length() & 1) == 1, use w -> (w.length() % 2) != 0
// Instead of String::toUpperCase, use w -> w.toUpperCase()
//ENDREMOVE
assertEquals("[BRAVO, CHARLIE, DELTA, FOXTROT]", result.toString());
}
// Hint 1:
// <editor-fold defaultstate="collapsed">
// Use filter() and map().
// </editor-fold>
// Hint 2:
// <editor-fold defaultstate="collapsed">
// Use collect() to create the result list.
// </editor-fold>
/**
* Take the third through fifth words of the list, extract the
* second letter from each, and join them, separated by commas,
* into a single string. Watch for off-by-one errors.
*/
@Test
public void ex07_joinStreamRange() {
List<String> input = new ArrayList<>(Arrays.asList(
"alfa", "bravo", "charlie", "delta", "echo", "foxtrot"));
//TODO//String result = "";
//BEGINREMOVE
String result =
input.stream()
.skip(2)
.limit(3)
.map(word -> word.substring(1, 2))
.collect(Collectors.joining(","));
//ENDREMOVE
assertEquals("h,e,c", result);
}
// Hint 1:
// <editor-fold defaultstate="collapsed">
// Use Stream.skip() and Stream.limit().
// </editor-fold>
// Hint 2:
// <editor-fold defaultstate="collapsed">
// Use Collectors.joining().
// </editor-fold>
/**
* Count the number of lines in the text file. (Remember to
* use the BufferedReader named "reader" that has already been
* opened for you.)
*
* @throws IOException
*/
@Test
public void ex08_countLinesInFile() throws IOException {
//TODO//long count = 0;
//BEGINREMOVE
long count =
reader.lines()
.count();
//ENDREMOVE
assertEquals(14, count);
}
// Hint 1:
// <editor-fold defaultstate="collapsed">
// Use BufferedReader.lines() to get a stream of lines.
// </editor-fold>
// Hint 2:
// <editor-fold defaultstate="collapsed">
// Use Stream.count().
// </editor-fold>
/**
* Find the length of the longest line in the text file.
*
* @throws IOException
*/
@Test
public void ex09_findLengthOfLongestLine() throws IOException {
//TODO//int longestLength = 0;
//BEGINREMOVE
int longestLength =
reader.lines()
.mapToInt(String::length)
.max()
.getAsInt();
//ENDREMOVE
assertEquals(53, longestLength);
}
// Hint 1:
// <editor-fold defaultstate="collapsed">
// Use Stream.mapToInt() to convert to IntStream.
// </editor-fold>
// Hint 2:
// <editor-fold defaultstate="collapsed">
// Look at java.util.OptionalInt to get the result.
// </editor-fold>
/**
* Find the longest line in the text file.
*
* @throws IOException
*/
@Test
public void ex10_findLongestLine() throws IOException {
//TODO//String longest = null;
//BEGINREMOVE
String longest =
reader.lines()
.max(Comparator.comparingInt(String::length))
.orElse("");
// Alternative:
// Instead of Comparator.comparingInt(String::length), one could
// use something like:
// (s1, s2) -> Integer.compare(s1.length(), s2.length())
//ENDREMOVE
assertEquals("Feed'st thy light's flame with self-substantial fuel,", longest);
}
// Hint 1:
// <editor-fold defaultstate="collapsed">
// Use Stream.max() with a Comparator.
// </editor-fold>
// Hint 2:
// <editor-fold defaultstate="collapsed">
// Use static methods on Comparator to help create a Comparator instance.
// </editor-fold>
/**
* Select the list of words from the input list whose length is greater than
* the word's position in the list (starting from zero) .
*/
@Test
public void ex11_selectByLengthAndPosition() {
List<String> input = new ArrayList<>(Arrays.asList(
"alfa", "bravo", "charlie", "delta", "echo", "foxtrot", "golf", "hotel"));
//TODO//List<String> result = null;
//BEGINREMOVE
List<String> result =
IntStream.range(0, input.size())
.filter(pos -> input.get(pos).length() > pos)
.mapToObj(pos -> input.get(pos))
.collect(Collectors.toList());
//ENDREMOVE
assertEquals(Arrays.asList("alfa", "bravo", "charlie", "delta", "foxtrot"), result);
}
// Hint:
// <editor-fold defaultstate="collapsed">
// Instead of a stream of words (Strings), run an IntStream of positions.
// </editor-fold>
/**
* Given two lists of Integer, compute a third list where each element is the
* difference between the corresponding elements of the two input lists
* (first minus second).
*/
@Test
public void ex12_listDifference() {
List<Integer> one = Arrays.asList(3, 1, 4, 1, 5, 9, 2, 6, 5, 3);
List<Integer> two = Arrays.asList(2, 7, 1, 8, 2, 8, 1, 8, 2, 8);
//TODO//List<Integer> result = null;
//BEGINREMOVE
List<Integer> result =
IntStream.range(0, one.size())
.mapToObj(i -> one.get(i) - two.get(i))
.collect(Collectors.toList());
//ENDREMOVE
assertEquals(Arrays.asList(1, -6, 3, -7, 3, 1, 1, -2, 3, -5), result);
}
// Hint 1:
// <editor-fold defaultstate="collapsed">
// Run an IntStream of list positions (indexes).
// </editor-fold>
// Hint 2:
// <editor-fold defaultstate="collapsed">
// Deal with boxed Integers either by casting or by using mapToObj().
// </editor-fold>
// ========================================================
// END OF EXERCISES
// TEST INFRASTRUCTURE IS BELOW
// ========================================================
private BufferedReader reader;
@Before
public void z_setUpBufferedReader() throws IOException {
reader = Files.newBufferedReader(
Paths.get("SonnetI.txt"), StandardCharsets.UTF_8);
}
@After
public void z_closeBufferedReader() throws IOException {
reader.close();
}
}