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first commit · stevencoding/java8-tutorial@ef919c8 · GitHub

/ java8-tutorial Public
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‎.gitignore‎

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.DS_Store
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.idea
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*.iml
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out

‎src/com/winterbe/java8/Annotations1.java‎

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package com.winterbe.java8;
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import java.lang.annotation.ElementType;
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import java.lang.annotation.Repeatable;
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import java.lang.annotation.Retention;
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import java.lang.annotation.RetentionPolicy;
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import java.lang.annotation.Target;
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/**
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* @author Benjamin Winterberg
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*/
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public class Annotations1 {
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@Target({ElementType.TYPE_PARAMETER, ElementType.TYPE_USE})
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@interface MyAnnotation {
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}
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@Retention(RetentionPolicy.RUNTIME)
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@interface Hints {
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Hint[] value();
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}
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@Repeatable(Hints.class)
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@Retention(RetentionPolicy.RUNTIME)
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@interface Hint {
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String value();
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}
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@Hint("hint1")
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@Hint("hint2")
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class Person {
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}
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public static void main(String[] args) {
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Hint hint = Person.class.getAnnotation(Hint.class);
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System.out.println(hint); // null
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Hints hints1 = Person.class.getAnnotation(Hints.class);
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System.out.println(hints1.value().length); // 2
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Hint[] hints2 = Person.class.getAnnotationsByType(Hint.class);
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System.out.println(hints2.length); // 2
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}
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}

‎src/com/winterbe/java8/Concurrency1.java‎

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package com.winterbe.java8;
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import java.util.UUID;
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import java.util.concurrent.ConcurrentHashMap;
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/**
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* @author Benjamin Winterberg
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*/
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public class Concurrency1 {
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public static void main(String[] args) {
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ConcurrentHashMap<Integer, UUID> concurrentHashMap = new ConcurrentHashMap<>();
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for (int i = 0; i < 100; i++) {
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concurrentHashMap.put(i, UUID.randomUUID());
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}
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int threshold = 1;
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concurrentHashMap.forEachValue(threshold, System.out::println);
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concurrentHashMap.forEach((id, uuid) -> {
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if (id % 10 == 0) {
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System.out.println(String.format("%s: %s", id, uuid));
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}
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});
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UUID searchResult = concurrentHashMap.search(threshold, (id, uuid) -> {
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if (String.valueOf(uuid).startsWith(String.valueOf(id))) {
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return uuid;
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}
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return null;
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});
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System.out.println(searchResult);
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}
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}

‎src/com/winterbe/java8/Interface1.java‎

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package com.winterbe.java8;
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/**
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* @author Benjamin Winterberg
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*/
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public class Interface1 {
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interface Formula {
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double calculate(int a);
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default double sqrt(int a) {
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return Math.sqrt(positive(a));
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}
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static int positive(int a) {
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return a > 0 ? a : 0;
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}
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}
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public static void main(String[] args) {
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Formula formula1 = new Formula() {
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@Override
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public double calculate(int a) {
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return sqrt(a * 100);
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}
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};
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formula1.calculate(100); // 100.0
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formula1.sqrt(-23); // 0.0
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Formula.positive(-4); // 0.0
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// Formula formula2 = (a) -> sqrt( a * 100);
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}
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}

‎src/com/winterbe/java8/Lambda1.java‎

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package com.winterbe.java8;
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import java.util.Arrays;
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import java.util.Collections;
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import java.util.Comparator;
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import java.util.List;
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/**
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* @author Benjamin Winterberg
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*/
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public class Lambda1 {
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public static void main(String[] args) {
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List<String> names = Arrays.asList("peter", "anna", "mike", "xenia");
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Collections.sort(names, new Comparator<String>() {
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@Override
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public int compare(String a, String b) {
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return b.compareTo(a);
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}
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});
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Collections.sort(names, (String a, String b) -> {
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return b.compareTo(a);
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});
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Collections.sort(names, (String a, String b) -> b.compareTo(a));
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Collections.sort(names, (a, b) -> b.compareTo(a));
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System.out.println(names);
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}
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}

‎src/com/winterbe/java8/Lambda2.java‎

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package com.winterbe.java8;
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/**
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* @author Benjamin Winterberg
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*/
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public class Lambda2 {
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@FunctionalInterface
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public static interface Converter<F, T> {
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T convert(F from);
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}
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static class Something {
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String startsWith(String s) {
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return String.valueOf(s.charAt(0));
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}
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}
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interface PersonFactory<P extends Person> {
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P create(String firstName, String lastName);
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}
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public static void main(String[] args) {
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Converter<String, Integer> integerConverter1 = (from) -> Integer.valueOf(from);
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Integer converted1 = integerConverter1.convert("123");
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System.out.println(converted1); // result: 123
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// method reference
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Converter<String, Integer> integerConverter2 = Integer::valueOf;
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Integer converted2 = integerConverter2.convert("123");
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System.out.println(converted2); // result: 123
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Something something = new Something();
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Converter<String, String> stringConverter = something::startsWith;
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String converted3 = stringConverter.convert("Java");
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System.out.println(converted3); // result J
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// constructor reference
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PersonFactory<Person> personFactory = Person::new;
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Person person = personFactory.create("Peter", "Parker");
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}
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}

‎src/com/winterbe/java8/Lambda3.java‎

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package com.winterbe.java8;
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import java.util.Comparator;
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import java.util.Objects;
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import java.util.UUID;
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import java.util.concurrent.Callable;
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import java.util.function.Consumer;
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import java.util.function.Function;
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import java.util.function.Predicate;
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import java.util.function.Supplier;
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/**
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* Common standard functions from the Java API.
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*
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* @author Benjamin Winterberg
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*/
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public class Lambda3 {
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@FunctionalInterface
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interface Fun {
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void foo();
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}
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public static void main(String[] args) throws Exception {
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// Predicates
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Predicate<String> predicate = (s) -> s.length() > 0;
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predicate.test("foo"); // true
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predicate.negate().test("foo"); // false
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Predicate<Boolean> nonNull = Objects::nonNull;
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Predicate<Boolean> isNull = Objects::isNull;
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Predicate<String> isEmpty = String::isEmpty;
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Predicate<String> isNotEmpty = isEmpty.negate();
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// Functions
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Function<String, Integer> toInteger = Integer::valueOf;
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Function<String, String> backToString = toInteger.andThen(String::valueOf);
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backToString.apply("123"); // "123"
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// Suppliers
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Supplier<Person> personSupplier = Person::new;
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personSupplier.get(); // new Person
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// Consumers
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Consumer<Person> greeter = (p) -> System.out.println("Hello, " + p.firstName);
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greeter.accept(new Person("Luke", "Skywalker"));
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// Comparators
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Comparator<Person> comparator = (p1, p2) -> p1.firstName.compareTo(p2.firstName);
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Person p1 = new Person("John", "Doe");
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Person p2 = new Person("Alice", "Wonderland");
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comparator.compare(p1, p2); // > 0
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comparator.reversed().compare(p1, p2); // < 0
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// Runnables
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Runnable runnable = () -> System.out.println(UUID.randomUUID());
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runnable.run();
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// Callables
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Callable<UUID> callable = UUID::randomUUID;
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callable.call();
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}
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}

‎src/com/winterbe/java8/Lambda4.java‎

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package com.winterbe.java8;
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/**
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* @author Benjamin Winterberg
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*/
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public class Lambda4 {
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static int outerStaticNum;
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int outerNum;
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void testScopes() {
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int num = 1;
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Lambda2.Converter<Integer, String> stringConverter =
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(from) -> String.valueOf(from + num);
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String convert = stringConverter.convert(2);
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System.out.println(convert); // 3
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Lambda2.Converter<Integer, String> stringConverter2 = (from) -> {
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outerNum = 13;
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return String.valueOf(from);
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};
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String[] array = new String[1];
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Lambda2.Converter<Integer, String> stringConverter3 = (from) -> {
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array[0] = "Hi there";
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return String.valueOf(from);
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};
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stringConverter3.convert(23);
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System.out.println(array[0]);
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}
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public static void main(String[] args) {
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new Lambda4().testScopes();
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}
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}

‎src/com/winterbe/java8/LocalDate1.java‎

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package com.winterbe.java8;
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import java.time.DayOfWeek;
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import java.time.LocalDate;
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import java.time.Month;
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import java.time.format.DateTimeFormatter;
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import java.time.format.FormatStyle;
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import java.time.temporal.ChronoUnit;
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import java.util.Locale;
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/**
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* @author Benjamin Winterberg
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*/
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public class LocalDate1 {
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public static void main(String[] args) {
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LocalDate today = LocalDate.now();
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LocalDate tomorrow = today.plus(1, ChronoUnit.DAYS);
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LocalDate yesterday = tomorrow.minusDays(2);
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System.out.println(today);
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System.out.println(tomorrow);
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System.out.println(yesterday);
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LocalDate independenceDay = LocalDate.of(2014, Month.JULY, 4);
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DayOfWeek dayOfWeek = independenceDay.getDayOfWeek();
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System.out.println(dayOfWeek); // FRIDAY
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DateTimeFormatter germanFormatter =
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DateTimeFormatter
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.ofLocalizedDate(FormatStyle.MEDIUM)
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.withLocale(Locale.GERMAN);
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LocalDate xmas = LocalDate.parse("24.12.2014", germanFormatter);
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System.out.println(xmas); // 2014-12-24
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}
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}

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