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samshosamsho
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【Guava】lambda
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‎Guava/.idea/workspace.xml‎

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‎Guava/Guava.iml‎

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</content>
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<orderEntry type="inheritedJdk" />
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<orderEntry type="sourceFolder" forTests="false" />
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<orderEntry type="library" scope="TEST" name="Maven: junit:junit:4.11" level="project" />
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<orderEntry type="library" scope="TEST" name="Maven: org.hamcrest:hamcrest-core:1.3" level="project" />
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<orderEntry type="library" name="Maven: com.google.guava:guava:18.0" level="project" />
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</component>
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</module>

‎Guava/pom.xml‎

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<properties>
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<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
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<guava.version>18.0</guava.version>
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<log4j.version>2.5</log4j.version>
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<fileupload.version>1.2.2</fileupload.version>
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<junit.version>4.11</junit.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>${junit.version}</version>
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<scope>test</scope>
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</dependency>
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<dependency>
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<groupId>com.google.guava</groupId>
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<artifactId>guava</artifactId>

‎Guava/src/main/java/com.guava/lambda/GuavaLambda.java‎

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package com.guava.lambda;
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import com.entity.Person;
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import com.google.common.base.Function;
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import com.google.common.base.Predicate;
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import com.google.common.base.Predicates;
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import com.google.common.collect.Collections2;
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import com.google.common.collect.Iterables;
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import com.google.common.collect.Lists;
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import java.util.ArrayList;
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import java.util.List;
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import static com.google.common.base.Predicates.and;
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/**
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* ClassName: GuavaLambda
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* Description:
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* Date: 2016/5/28 9:17
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*
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* @author SAM SHO
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* @version V1.0
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*/
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public class GuavaLambda {
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public static void main(String[] args) {
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GuavaLambda lambda = new GuavaLambda();
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// lambda.test();
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// lambda.test1();
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// lambda.test2();
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lambda.test3();
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}
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public void test() {
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List<Person> people = new ArrayList<Person>();
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people.add(new Person("bowen",27));
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people.add(new Person("bob", 20));
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people.add(new Person("Katy", 18));
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people.add(new Person("Logon", 24));
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System.out.println(people);
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/** 选取年龄 > 20 **/
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List<Person> oldPeople = new ArrayList<Person>();
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for (Person person : people) {
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if (person.getAge() >= 20) {
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oldPeople.add(person);
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}
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}
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System.out.println(oldPeople);
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}
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/**
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* newArrayList()方法
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*/
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public void test1() {
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List<Person> people = Lists.newArrayList(new Person("bowen", 27),
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new Person("bob", 20),
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new Person("Katy", 18),
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new Person("Logon", 24));
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System.out.println(people);
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/**
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* 这就是典型的filter模式。filter即从一个集合中根据一个条件筛选元素。
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* 其中person.getAge() >=20就是这个条件。Guava为这种模式提供了一个filter的方法。所以我们可以这样写。
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*
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* Predicate 里面只有一个apply方法，接收一个泛型的实参，返回一个boolean值。
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* 由于java世界中函数并不是一等公民，所以我们无法直接传递一个条件函数，只能通过Predicate这个类包装一下。
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*
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* Iterables.filter 与 Collections2.filter 一样可以用
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*
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**/
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List<Person> oldPeople = Lists.newArrayList(Iterables.filter(people, new Predicate<Person>() {
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public boolean apply(Person person) {
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return person.getAge() >= 20;
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}
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}));
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System.out.println(oldPeople);
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}
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/**
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* And Predicate
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*/
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public void test2() {
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List<Person> people = Lists.newArrayList(new Person("bowen", 27),
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new Person("bob", 20),
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new Person("Katy", 18),
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new Person("Logon", 24));
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System.out.println(people);
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List<Person> filteredPeople = Lists.newArrayList(Collections2.filter(people, Predicates.and(ageBiggerThan(20), nameContains("b"))));
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System.out.println(filteredPeople);
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}
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private Predicate<Person> ageBiggerThan(final int age) {
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return new Predicate<Person>() {
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public boolean apply(Person person) {
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return person.getAge() >= age;
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}
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};
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}
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private Predicate<Person> nameContains(final String str) {
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return new Predicate<Person>() {
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public boolean apply(Person person) {
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return person.getName().contains(str);
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}
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};
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}
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/**
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* Map(transform):map pattern
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* 就是将数组中的所有元素映射为另一种元素的列表
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**/
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public void test3() {
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List<Person> people = Lists.newArrayList(new Person("bowen", 27),
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new Person("bob", 20),
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new Person("Katy", 18),
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new Person("Logon", 24));
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/*求People列表中的所有人名。程序员十有八九都会这样写。*/
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List<String> names = new ArrayList<String>();
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for (Person person : people) {
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names.add(person.getName());
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}
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System.out.println(names);
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/**
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* Function是另外一种用于封装函数的接口对象。
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* 它与Predicate非常相似，但不同的是它接收两个泛型，
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* apply方法接收一种泛型实参，返回值是另一种泛型值。正是这个apply方法定义了数组间元素一对一的map规则。
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**/
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List<String> names2 = Lists.newArrayList(Collections2.transform(people, new Function<Person, String>() {
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public String apply(Person person) {
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return person.getName();
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}
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}));
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System.out.println(names2);
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}
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}

‎Guava/src/main/java/com/entity/Person.java‎

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package com.entity;
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public class Person {
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public String getName() {
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return name;
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}
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public void setName(String name) {
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this.name = name;
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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 void setAge(int age) {
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this.age = age;
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}
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private String name;
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private int age;
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public Person(String name, int age) {
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this.name = name;
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this.age = age;
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}
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@Override
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public String toString() {
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return "Person{" +
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"name='" + name + '\'' +
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", age=" + age +
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'}';
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}
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}

‎Guava/src/main/java/com/entity/Presider.java‎

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public Presider() {}
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public int getId() {
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public Presider(String name, String jobNumber) {
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this.name = name;
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this.jobNumber = jobNumber;
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}
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public int getId() {
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return id;
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}
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