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‎.gitignore‎

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# For STS/Eclipse
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.classpath
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.project
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.settings/
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.springBeans
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Servers
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bin
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# IntelliJ IDEA
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.idea/
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*.iml
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*.iws
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# Maven
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target/
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# For Mac OS X
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.DS_Store
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# Logging
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*.log

‎pom.xml‎

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<project xmlns="http://maven.apache.org/POM/4.0.0"
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xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<modelVersion>4.0.0</modelVersion>
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<groupId>org.bsnyder.java18.examples</groupId>
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<artifactId>java18-examples</artifactId>
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<version>1.0-SNAPSHOT</version>
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<packaging>jar</packaging>
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<name>java18-examples</name>
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<url>http://maven.apache.org</url>
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<properties>
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<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
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<maven-compiler-plugin-version>3.2</maven-compiler-plugin-version>
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</properties>
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<dependencies>
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<dependency>
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<groupId>junit</groupId>
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<artifactId>junit</artifactId>
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<version>4.12</version>
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<scope>test</scope>
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</dependency>
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</dependencies>
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<build>
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<pluginManagement>
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<plugins>
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<plugin>
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<groupId>org.apache.maven.plugins</groupId>
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<artifactId>maven-compiler-plugin</artifactId>
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<version>${maven-compiler-plugin-version}</version>
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<configuration>
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<source>1.8</source>
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<target>1.8</target>
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</configuration>
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</plugin>
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</plugins>
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</pluginManagement>
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</build>
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</project>

‎src/main/java/org/bsnyder/java18/examples/Java8LambdasDemo.java‎

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package org.bsnyder.java18.examples;
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import java.util.Arrays;
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import java.util.List;
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import java.util.function.Consumer;
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interface Executable {
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int execute(int a);
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}
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class Runner {
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public int run(Executable e) {
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System.out.println("Executing code block...");
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int x = e.execute(999);
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System.out.println(x);
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return x;
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}
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}
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public class Java8LambdasDemo
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{
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public static void main( String[] args ) {
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// List<Integer> numbers = Arrays.asList(1,2,3,4,5,6,7,8,9);
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//
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// numbers.forEach(new Consumer<Integer>() {
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// @Override
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// public void accept(Integer integer) {
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// System.out.println(integer);
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// }
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// });
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Runner r = new Runner();
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r.run(new Executable() {
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@Override
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public int execute(int a) {
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System.out.println("Simple Executable");
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return a+2;
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}
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});
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System.out.println("==========================");
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/*
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r.run(() -> {
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System.out.println("Testing a lambda");
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System.out.println();
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return 3;
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});
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*/
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r.run(a -> {
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System.out.println("Adding a+3");
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return a+3;
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});
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}
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}

‎src/main/java/org/bsnyder/java18/examples/Java8LambdasDemo2.java‎

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package org.bsnyder.java18.examples;
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import java.util.Arrays;
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import java.util.List;
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import java.util.stream.Collectors;
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class Person {
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String name;
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String country;
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int age;
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public Person(String name, String country, int age) {
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this.name = name;
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this.country = country;
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this.age = age;
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}
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public String getName() {
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return name;
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}
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public String getCountry() {
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return country;
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}
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public int getAge() {
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return age;
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}
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public String toString() {
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return "{Person => name: " + name + " country: " + country + " age: " + age + "}";
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}
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}
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public class Java8LambdasDemo2 {
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public static void main(String[] args) {
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List<Person> people = Arrays.asList(
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new Person("Bailey", "USA", 12),
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new Person("Jade", "USA", 16),
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new Person("Janene", "Mexico", 43),
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new Person("Bruce", "Canada", 43),
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new Person("Diane", "Germany", 64),
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new Person("Jim", "Germany", 64),
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new Person("Susan", "USA", 62),
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new Person("John", "Canada", 64));
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System.out.println("==== People from the US :: filter ====");
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people.stream()
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.filter(person -> person.getCountry().equals("USA"))
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.map((Person person) -> "name: " + person.getName() + " country: " + person.getCountry())
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.forEach(person -> System.out.println(person));
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System.out.println("\n==== People not from the US :: filter ====");
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people.stream()
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.filter(person -> !person.getCountry().equals("USA"))
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.map((Person person) -> "name: " + person.getName() + " country: " + person.getCountry())
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.forEach(person -> System.out.println(person));
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System.out.println("\n==== People from the US :: collect w/ partitioningBy ====");
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System.out.println(people.stream()
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.collect(Collectors.partitioningBy((Person p) -> p.getCountry().equals("USA"))));
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System.out.println("\n==== People from the US :: collect w/ groupingBy ====");
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System.out.println(people.stream()
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.collect(Collectors.groupingBy((Person p) -> p.getCountry().equals("USA"))));
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System.out.println("\n==== People from the US :: collect w/ groupingBy and counting ====");
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System.out.println(people.stream()
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.collect(Collectors.groupingBy((Person p) -> p.getCountry().equals("USA"), Collectors.counting())));
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System.out.println("\n==== People from the US :: collect w/ groupingBy and counting ====");
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System.out.println(people.stream()
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.collect(Collectors.groupingBy((Person p) -> p.getCountry().equals("USA"), Collectors.counting())));
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System.out.println("\n==== People in each country :: collect w/ partitioningBy and counting ====");
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System.out.println(people.stream()
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.collect(Collectors.groupingBy((Person p) -> p.getCountry())));
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System.out.println(people.stream()
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.collect(Collectors.groupingBy((Person p) -> p.getCountry(), Collectors.counting())));
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System.out.println("\n==== People in USA and non-USA :: collect w/ partitioningBy and mapping ====");
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System.out.println(people.stream()
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.collect(Collectors.partitioningBy((Person p) -> p.getCountry().equals("USA"),
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Collectors.mapping(p -> p.getName().toUpperCase(),
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Collectors.toList()))));
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System.out.println("\n==== People in USA and non-USA :: collect w/ groupingBy and mapping ====");
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System.out.println(people.stream()
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.collect(Collectors.groupingBy((Person p) -> p.getCountry(),
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Collectors.mapping(p -> p.getName().toUpperCase(),
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Collectors.toList()))));
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}
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}

‎src/main/java/org/bsnyder/java18/examples/PredicateDemo.java‎

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package org.bsnyder.java18.examples;
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import java.util.ArrayList;
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import java.util.Arrays;
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import java.util.List;
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import java.util.function.Predicate;
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class MyPredicate<T> {
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public List<T> testPredicate(Predicate<T> p, List<T> numbers) {
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List<T> answer = new ArrayList<>();
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numbers.forEach( x -> {
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if (p.test(x)) {
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answer.add(x);
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}
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});
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return answer;
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}
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public List<T> testPredicateNegate(Predicate<T> p, List<T> l) {
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List<T> answer = new ArrayList<>();
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/*
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Q: Why does external iteration not result in proper negation?
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l.forEach( x -> {
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if (p.negate().test(x));
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answer.add(x);
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});
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*/
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for (T t : l) {
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if (p.negate().test(t)) answer.add(t);
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}
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return answer;
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}
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public List<T> testPredicateOr(Predicate<T> p1, Predicate<T> p2, List<T> l) {
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List<T> answer = new ArrayList<>();
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for( T t : l) {
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if (p1.or(p2).test(t)) answer.add(t);
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}
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return answer;
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}
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public List<T> testPredicateAnd(Predicate<T> p1, Predicate<T> p2, List<T> l) {
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List<T> answer = new ArrayList<>();
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for( T t : l) {
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if (p1.and(p2).test(t)) answer.add(t);
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}
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return answer;
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}
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}
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/**
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* Created by bsnyder on 1/13/15.
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*/
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public class PredicateDemo {
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public static void main(String[] args) {
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List<Integer> numbers = Arrays.asList(0,1,2,3,4,5,6,7,8,9,10,11,12,13);
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MyPredicate<Integer> intPredicate = new MyPredicate<Integer>();
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System.out.println(" All numbers: " + intPredicate.testPredicate(x -> true, numbers));
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System.out.println("Even numbers: " + intPredicate.testPredicate(x -> (x & 1) == 0, numbers));
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System.out.println(" Odd numbers: " + intPredicate.testPredicate(x -> (x & 1) == 1, numbers));
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System.out.println();
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System.out.println(" Negate all numbers: " + intPredicate.testPredicateNegate(x -> true, numbers));
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System.out.println("Negate even numbers: " + intPredicate.testPredicateNegate(x -> (x & 1) == 0, numbers));
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System.out.println(" Negate odd numbers: " + intPredicate.testPredicateNegate(x -> (x & 1) == 1, numbers));
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System.out.println("###################################################");
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MyPredicate<String> stringPredicate = new MyPredicate<>();
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List<String> strings = Arrays.asList("one", "two", "three", "four", "five", "six", "seven", "eight");
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System.out.println("All strings: " + stringPredicate.testPredicate(x -> true, strings));
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System.out.println("Contains ee: " + stringPredicate.testPredicate(x -> x.contains("ee"), strings));
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System.out.println(" Contains t: " + stringPredicate.testPredicate(x -> x.contains("t"), strings));
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System.out.println();
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System.out.println("Negate all strings: " + stringPredicate.testPredicateNegate(x -> true, strings));
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System.out.println("Negate contains ee: " + stringPredicate.testPredicateNegate(x -> x.contains("ee"), strings));
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System.out.println(" Negate contains t: " + stringPredicate.testPredicateNegate(x -> x.contains("t"), strings));
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System.out.println("###################################################");
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MyPredicate<Object> objPredicate = new MyPredicate<>();
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List<Object> objects = Arrays.asList(new String("one"), new String("two"), new StringBuilder("three"));
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System.out.println(" All objects: " + objPredicate.testPredicate(x -> true, objects));
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System.out.println(" Type String: " + objPredicate.testPredicate(x -> x instanceof String, objects));
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System.out.println("Type StringBuilder: " + objPredicate.testPredicate(x -> x instanceof StringBuilder, objects));
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System.out.println();
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System.out.println(" Negate all objects: " + objPredicate.testPredicateNegate(x -> true, objects));
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System.out.println(" Negate type String: " + objPredicate.testPredicateNegate(x -> x instanceof String, objects));
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System.out.println("Negate type StringBuilder: " + objPredicate.testPredicateNegate(x -> x instanceof StringBuilder, objects));
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System.out.println("###################################################");
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System.out.println("Even or odd numbers: " +
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intPredicate.testPredicateOr(x -> (x & 1) == 0, x -> (x & 1) == 1, numbers));
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System.out.println("Even or odd numbers: " +
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intPredicate.testPredicateAnd(x -> (x & 1) == 0, x -> (x & 1) == 1, numbers));
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}
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}
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‎src/test/java/org/bsnyder/java18/examples/AppTest.java‎

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package org.bsnyder.java18.examples;
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import org.junit.Test;
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import static org.junit.Assert.assertTrue;
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/**
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* Unit test for simple Java8LambdasDemo.
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*/
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public class AppTest
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{
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/**
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* Rigourous Test :-)
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*/
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@Test
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public void testApp() {
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assertTrue( true );
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}
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}

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