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Create Customer.java
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‎BecomingFunctional/Customer.java

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package chapter3;
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import java.util.ArrayList;
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import java.util.List;
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public class Customer {
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// 모든 고객 정보리스트
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static public ArrayList<Customer> allCustomers = new ArrayList<Customer>();
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public Integer id = 0;
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public String name = "";
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public String address = "";
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public String state = "";
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public String primaryContact = "";
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public String domain = "";
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public Boolean enabled = true;
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public Contract contract;
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public Customer() {
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}
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/**
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* 초기화
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*/
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static {
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for (int i = 0; i < 10; i++) {
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Customer customer = new Customer();
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customer.name = "name : " + i;
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customer.address = "address : " + i;
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customer.state = "state : " + i;
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customer.primaryContact = "primaryContact : " + i;
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customer.domain = "domain : " + i;
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customer.enabled = i % 2 == 0;
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allCustomers.add(customer);
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}
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}
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public Customer setCustomerId(Integer customer_id) {
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this.id = customer_id;
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return this;
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}
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public Customer setName(String name) {
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this.name = name;
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return this;
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}
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public Customer setState(String state) {
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this.state = state;
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return this;
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}
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public Customer setDomain(String domain) {
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this.domain = domain;
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return this;
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}
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public Customer setEnabled(Boolean enabled) {
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this.enabled = enabled;
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return this;
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}
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public Customer setContract(Contract contract) {
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this.contract = contract;
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return this;
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}
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/**
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* 고객정보를 가지고오는 정보 클래스
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*/
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public static List<String> getEnabledCustomerAddresses() {
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return getEnabledCustomerField(new Function1<Customer, String>() {
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public String call(Customer customer) {
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return customer.address;
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}
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});
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}
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public static List<String> getEnabledCustomerNames() {
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return getEnabledCustomerField(new Function1<Customer, String>() {
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public String call(Customer customer) {
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return customer.name;
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}
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});
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}
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public static List<String> getEnabledCustomerStates() {
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return getEnabledCustomerField(new Function1<Customer, String>() {
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public String call(Customer customer) {
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return customer.state;
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}
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});
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}
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public static List<String> getEnabledCustomerPrimaryContacts() {
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return getEnabledCustomerField(new Function1<Customer, String>() {
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public String call(Customer customer) {
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return customer.primaryContact;
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}
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});
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}
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public static List<String> getEnabledCustomerDomains() {
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return getEnabledCustomerField(new Function1<Customer, String>() {
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public String call(Customer customer) {
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return customer.domain;
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}
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});
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}
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public static <B> List<B> getEnabledCustomerField(Function1<Customer, B> func) {
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ArrayList<B> outList = new ArrayList<B>();
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for (Customer customer : Customer.allCustomers) {
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if (customer.enabled) {
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outList.add(func.call(customer));
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}
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}
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return outList;
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}
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/**
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* id에 해당하는 고객이 존재하면 반환하고, 그렇지 않으면 null을 반환하는 간단한 메소드
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*
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* @param customer_id
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* @return
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*/
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public static Customer getCustomerById(Integer customer_id) {
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for (Customer customer : Customer.allCustomers) {
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if (customer.id == customer_id) {
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return customer;
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}
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}
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// 이걸 대체 무슨 의미로 받아들여야 할까요?
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// - 에러인가? 못찾았다는 것인가?
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return null;
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}
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/**
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* 프로그램 오류는 아닌데도 호출자에게 ‘고객을 찾지 못했으니 예외를 던지는 거 야’라고 말하는 건 좀 이상하므로 위의 getCustomerById 보완
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*
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* @param customer_id
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* @return
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*/
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public static ArrayList<Customer> getCustomerListById(Integer customer_id) {
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ArrayList<Customer> outList = new ArrayList<Customer>();
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for (Customer customer : Customer.allCustomers) {
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if (customer.id == customer_id) {
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outList.add(customer);
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}
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}
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return outList;
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}
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/**
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* 일급함수이지만 순수함수는 아니다. 참조된 allCustomers값에 의해서 변경될 소지가 있기 때문이다
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*
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* @param func
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* @return
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*/
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public static ArrayList<Customer> filter(Function1<Customer, Boolean> func) {
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ArrayList<Customer> outList = new ArrayList<Customer>();
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for (Customer customer : Customer.allCustomers) {
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if (func.call(customer)) {
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outList.add(customer);
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}
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}
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return outList;
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}
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/**
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* filter 메소드를 이용해서 getCustomerListById 개선한 메소드
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* 함수를 더 작은 순수 함수들로 나누어 작성하면 코드의 전반적인 기능을 잘 이해하고 파악하는 데 도움이 될 수 있음
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*
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* @param customer_id
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* @return
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*/
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public static ArrayList<Customer> getCustomerListFilterById(final Integer customer_id) {
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return Customer.filter(new Function1<Customer, Boolean>() {
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public Boolean call(Customer customer) {
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return customer.id == customer_id;
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}
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});
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}
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/**
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*
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* @param function1
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* @param function2
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* @param <B>
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* @return
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*/
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public static <B> List<B> getField(Function1<Customer, Boolean> function1, Function1<Customer, B> function2) {
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ArrayList<B> outList = new ArrayList<B>();
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for (Customer customer : Customer.filter(function1)) {
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outList.add(function2.call(customer));
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}
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return outList;
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}
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// 테스트
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public static void main(String[] args) {
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List<String> addresses = getEnabledCustomerAddresses();
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for (String address : addresses) {
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System.out.print(address + " ");
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}
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System.out.println();
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List<String> names = getField(
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new Function1<Customer, Boolean>() {
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@Override
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public Boolean call(Customer in1) {
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return in1.enabled;
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}
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}, new Function1<Customer, String>() {
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@Override
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public String call(Customer in1) {
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return in1.name;
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}
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});
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for (String name : names) {
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System.out.print(name + " ");
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}
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}
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}

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