java8-tutorial/src/com/winterbe/java11/Misc.java at master · numatay/java8-tutorial · GitHub

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package com.winterbe.java11;

import java.io.File;

import java.io.FileOutputStream;

import java.io.IOException;

import java.util.List;

import java.util.Map;

import java.util.Optional;

import java.util.stream.Collectors;

import java.util.stream.Stream;

public class Misc {

@Deprecated(forRemoval = true)

String foo;

public static void main(String[] args) throws IOException {

collections();

strings();

optionals();

inputStreams();

streams();

}

private static void streams() {

System.out.println(Stream.ofNullable(null).count()); // 0

System.out.println(Stream.of(1, 2, 3, 2, 1)

.dropWhile(n -> n < 3)

.collect(Collectors.toList())); // [3, 2, 1]

System.out.println(Stream.of(1, 2, 3, 2, 1)

.takeWhile(n -> n < 3)

.collect(Collectors.toList())); // [1, 2]

}

private static void inputStreams() throws IOException {

var classLoader = ClassLoader.getSystemClassLoader();

var inputStream = classLoader.getResourceAsStream("com/winterbe/java11/dummy.txt");

var tempFile = File.createTempFile("dummy-copy", "txt");

try (var outputStream = new FileOutputStream(tempFile)) {

inputStream.transferTo(outputStream);

}

System.out.println(tempFile.length());

}

private static void optionals() {

System.out.println(Optional.of("foo").orElseThrow()); // foo

System.out.println(Optional.ofNullable(null).or(() -> Optional.of("bar")).get()); // bar

System.out.println(Optional.of("foo").stream().count()); // 1

}

private static void strings() {

System.out.println(" ".isBlank());

System.out.println(" Foo Bar ".strip()); // "Foo Bar"

System.out.println(" Foo Bar ".stripTrailing()); // " Foo Bar"

System.out.println(" Foo Bar ".stripLeading()); // "Foo Bar "

System.out.println("Java".repeat(3)); // "JavaJavaJava"

System.out.println("A\nB\nC".lines().count()); // 3

}

private static void collections() {

var list = List.of("A", "B", "C");

var copy = List.copyOf(list);

System.out.println(list == copy); // true

var map = Map.of("A", 1, "B", 2);

System.out.println(map);

}

java8-tutorial/src/com/winterbe/java11/Misc.java at master · numatay/java8-tutorial · GitHub

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