示例一：

跟示例三對(duì)比一下，盡量用示例三

List invoiceQueryBeanList= new ArrayList<>();

List invoices =Lists.newArrayList(Iterators.transform(

invoiceQueryBeanList.iterator(),new Function() {

@Nullable

@OverridepublicString apply(@Nullable InvoiceQueryBean input) {if(StringUtils.isNotBlank(input.getLoanInvoiceId())) {returninput.getLoanInvoiceId();

}else{return null;

}

}

}));

//去除空的

Iterators.removeIf(invoices.iterator(), StringUtils::isBlank);

示例二：

public static List getInvoiceQueryPojoList(ListinvoiceQueryBean) {returnLists.newArrayList(Iterators.transform(invoiceQueryBean.iterator(),

input-> input == null ? null:

PersonLoanInvoiceQueryPojo.Builder.getInstance()

.addLoanInvoiceId(input.getLoanInvoiceId())

.addUserName(input.getUserName())

.addCertificateKind(input.getCertificateKind())

.addCertificateNo(input.getCertificateNo()).addProductName(input.getProductName())

.addMerchantName(input.getMerchantName())

.addStoreName(input.getStoreName())

.addApplyDate(input.getApplyDate()).addLoanAmount(input.getLoanAmount())

.addLoanPeriod(input.getLoanPeriod()).addLoanPurpose(input.getLoanPurpose())

.addLoanDate(input.getLoanDate()).addRate(input.getRate())

.addChannelNo(input.getChannelNo())

.addApproveDate(input.getApproveDate())

.addReply(input.getReply())

.addMarketingCenterId(input.getMarketingCenterId()).build()));

}

public class PersonLoanInvoiceQueryPojo implementsSerializable{private static final long serialVersionUID = -408985049449365784L;privateString loanInvoiceId;privateString userId;privateString userName;public static classBuilder {private PersonLoanInvoiceQueryPojo instance = newPersonLoanInvoiceQueryPojo();privateBuilder(){}public staticBuilder getInstance() {return newBuilder();

}public staticBuilder getInstance(PersonLoanInvoiceQueryPojo instance){

Builder builder= newBuilder();

builder.instance=instance;returnbuilder;

}publicBuilder addLoanInvoiceId(String loanInvoiceId) {this.instance.setLoanInvoiceId(loanInvoiceId);return this;

}publicBuilder addUserId(String userId) {this.instance.setUserId(userId);return this;

}publicBuilder addUserName(String userName) {this.instance.setUserName(userName);return this;

}publicPersonLoanInvoiceQueryPojo build() {return this.instance;

}

}

setters();&getters();

}

示例三：方法引用

方法引用主要有三類：

(1)指向靜態(tài)方法的方法引用，(例如：Integer中的parseInt方法，寫作Integer::parseInt)

(2)指向任意類型實(shí)例方法的方法引用(例如String中的length方法，寫作String::length)

(3)指向現(xiàn)有對(duì)象的實(shí)例方法的方法引用(如下例)

importcom.google.common.collect.Iterators;importcom.google.common.collect.Lists;

List applySerialList= new ArrayList<>();

List operatorNoList =Lists.newArrayList(

Iterators.transform(applySerialList.iterator(), CreditPersonalInfoChangeApplySerial::getOperatorNo)); //這個(gè)叫做lambda的方法引用，注意方法引用的這個(gè)方法不需要()

示例四：

Lambad將List轉(zhuǎn)換成Map

importcom.google.common.collect.Maps;

List operatorInfoList= new ArrayList<>();

MapoperatorMap=Maps.uniqueIndex(operatorInfoList.iterator(), QueryUserAppInfoByUserIdListPojo::getUserId);public class QueryUserAppInfoByUserIdListPojo implementsSerializable {private static final long serialVersionUID = 6876288995978264269L;privateString userId;publicString getUserId() {return this.userId;

}public voidsetUserId(String userId) {this.userId =userId;

}

}

示例五：

List list= new ArrayList<>();

list.forEach(input->{if(input.getCertificateKind().equals(EnumCertificateKind.RESIDENT_IDENTITY_CARD)) {

userCertificateMap.put(pojo.getUserId(), input);

}

});

示例六：

遍歷的時(shí)候需要使用到元素的索引，很可惜，Java8 的?Iterable?并沒(méi)有提供一個(gè)帶索引的?forEach?方法，自動(dòng)動(dòng)手寫一個(gè)滿足自己的需求。

importjava.util.Objects;importjava.util.function.BiConsumer;/*** Iterable 的工具類*/

public classIterables {public static voidforEach(

Iterable extends E> elements, BiConsumeraction) {

Objects.requireNonNull(elements);

Objects.requireNonNull(action);int index = 0;for(E element : elements) {

action.accept(index++, element);

}

}

}

public static void main(String[] args) throwsException {

List list = Arrays.asList("a", "b", "b", "c", "c", "c", "d", "d", "d", "f", "f", "g");

Iterables.forEach(list, (index, str)-> System.out.println(index + " -> " +str));

}

示例七：Iterators.find

注意：find()函數(shù)有兩個(gè)重載方法，其中一個(gè)是帶 defaultValue 的，注意如果別迭代的集合沒(méi)有符合條件的數(shù)據(jù)的話，一定要定義一個(gè)默認(rèn)值。否則會(huì)報(bào)NoSuchElementException異常

Iterators.find(pojoList.iterator(), input -> input != null, null);

參考：

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