Code samples

Author: winterbe

src/com/winterbe/java8/samples/misc/Files1.java

@@ -7,6 +7,7 @@
 import java.nio.file.Path;
 import java.nio.file.Paths;
 import java.util.List;
+import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
 /**
@@ -26,25 +27,26 @@ public static void main(String[] args) throws IOException {
  }
 
  private static void testReaderLines() throws IOException {
- try (BufferedReader reader =
- Files.newBufferedReader(Paths.get("res", "nashorn1.js"))) {
- long countPrints = reader.lines()
+ Path path = Paths.get("res/nashorn1.js");
+ try (BufferedReader reader = Files.newBufferedReader(path)) {
+ long countPrints = reader
+ .lines()
  .filter(line -> line.contains("print"))
  .count();
  System.out.println(countPrints);
  }
  }
 
  private static void testWriter() throws IOException {
- try (BufferedWriter writer =
-  Files.newBufferedWriter(Paths.get("res", "output.js"))) {
+ Path path = Paths.get("res/output.js");
+ try (BufferedWriter writer = Files.newBufferedWriter(path)) {
  writer.write("print('Hello World');");
  }
  }
 
  private static void testReader() throws IOException {
- try (BufferedReader reader =
-  Files.newBufferedReader(Paths.get("res", "nashorn1.js"))) {
+ Path path = Paths.get("res/nashorn1.js");
+ try (BufferedReader reader = Files.newBufferedReader(path)) {
  System.out.println(reader.readLine());
  }
  }
@@ -53,10 +55,11 @@ private static void testWalk() throws IOException {
  Path start = Paths.get("");
  int maxDepth = 5;
  try (Stream<Path> stream = Files.walk(start, maxDepth)) {
- long fileCount = stream
- .filter(path -> String.valueOf(path).endsWith(".js"))
- .count();
- System.out.format("JS files found: %s", fileCount);
+ String joined = stream
+ .map(String::valueOf)
+ .filter(path -> path.endsWith(".js"))
+ .collect(Collectors.joining("; "));
+ System.out.println("walk(): " + joined);
  }
  }
 
@@ -65,26 +68,36 @@ private static void testFind() throws IOException {
  int maxDepth = 5;
  try (Stream<Path> stream = Files.find(start, maxDepth, (path, attr) ->
  String.valueOf(path).endsWith(".js"))) {
- stream.sorted().forEach(System.out::println);
+ String joined = stream
+ .sorted()
+ .map(String::valueOf)
+ .collect(Collectors.joining("; "));
+ System.out.println("find(): " + joined);
  }
  }
 
  private static void testList() throws IOException {
- try (Stream<Path> stream = Files.list(Paths.get("/usr"))) {
- stream.sorted().forEach(System.out::println);
+ try (Stream<Path> stream = Files.list(Paths.get(""))) {
+ String joined = stream
+ .map(String::valueOf)
+ .filter(path -> !path.startsWith("."))
+ .sorted()
+ .collect(Collectors.joining("; "));
+ System.out.println("list(): " + joined);
  }
  }
 
  private static void testLines() throws IOException {
- try (Stream<String> stream = Files.lines(Paths.get("res", "nashorn1.js"))) {
+ try (Stream<String> stream = Files.lines(Paths.get("res/nashorn1.js"))) {
  stream
  .filter(line -> line.contains("print"))
+ .map(String::trim)
  .forEach(System.out::println);
  }
  }
 
  private static void testReadWriteLines() throws IOException {
- List<String> lines = Files.readAllLines(Paths.get("res", "nashorn1.js"));
+ List<String> lines = Files.readAllLines(Paths.get("res/nashorn1.js"));
  lines.add("print('foobar');");
  Files.write(Paths.get("res", "nashorn1-modified.js"), lines);
  }

src/com/winterbe/java8/samples/misc/Math1.java

@@ -30,28 +30,29 @@ private static void testUnsignedInt() {
  System.out.println(string2);
 
  try {
- System.out.println(Integer.parseInt(string, 10));
+ Integer.parseInt(string, 10);
  }
  catch (NumberFormatException e) {
- System.out.println("could not parse signed int of " + maxUnsignedInt);
+ System.err.println("could not parse signed int of " + maxUnsignedInt);
  }
  }
 
  private static void testMathExact() {
+ System.out.println(Integer.MAX_VALUE);
  System.out.println(Integer.MAX_VALUE + 1);
 
  try {
  Math.addExact(Integer.MAX_VALUE, 1);
  }
  catch (ArithmeticException e) {
- System.out.println(e.getMessage());
+ System.err.println(e.getMessage());
  }
 
  try {
  Math.toIntExact(Long.MAX_VALUE);
  }
- catch (Exception e) {
- System.out.println(e.getMessage());
+ catch (ArithmeticException e) {
+ System.err.println(e.getMessage());
  }
  }
 }

src/com/winterbe/java8/samples/misc/String1.java

@@ -1,7 +1,8 @@
 package com.winterbe.java8.samples.misc;
 
-import java.util.function.Predicate;
 import java.util.regex.Pattern;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
 
 /**
  * @author Benjamin Winterberg
@@ -16,29 +17,33 @@ public static void main(String[] args) {
  }
 
  private static void testChars() {
- String string = "foobar";
- string.chars()
- .filter(c -> c > 100)
- .mapToObj(c -> (char)c)
- .forEach(System.out::println);
+ String string = "foobar:foo:bar"
+ .chars()
+ .distinct()
+ .mapToObj(c -> String.valueOf((char) c))
+ .sorted()
+ .collect(Collectors.joining());
+ System.out.println(string);
  }
 
  private static void testPatternSplit() {
- Pattern.compile(":")
+ String string = Pattern.compile(":")
  .splitAsStream("foobar:foo:bar")
+ .filter(s -> s.contains("bar"))
  .sorted()
- .forEach(System.out::println);
+ .collect(Collectors.joining(":"));
+ System.out.println(string);
  }
 
  private static void testPatternPredicate() {
- Pattern pattern = Pattern.compile(".*123.*");
- Predicate<String> predicate = pattern.asPredicate();
- System.out.println(predicate.test("a123b"));
- System.out.println(predicate.test("boom"));
+ long count = Stream.of("bob@gmail.com", "alice@hotmail.com")
+  .filter(Pattern.compile(".*@gmail\\.com").asPredicate())
+  .count();
+ System.out.println(count);
  }
 
  private static void testJoin() {
- String string = String.join(";", "a", "b", "c", "d");
+ String string = String.join(":", "foobar", "foo", "bar");
  System.out.println(string);
  }
 }