guava java 1.8_Java8-Guava实战示例

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#guava java 1.8

本文介绍了Java8结合Guava库进行实战操作的多个示例，包括List转换、方法引用、Lambda表达式以及自定义遍历方式等。示例涵盖了Iterators、Lists、Maps的实用方法，展示了如何高效地处理数据。

示例一：

跟示例三对比一下，尽量用示例三

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

方法引用主要有三类：

(1)指向静态方法的方法引用，(例如：Integer中的parseInt方法，写作Integer::parseInt)

(2)指向任意类型实例方法的方法引用(例如String中的length方法，写作String::length)

(3)指向现有对象的实例方法的方法引用(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)); //这个叫做lambda的方法引用，注意方法引用的这个方法不需要()

示例四：

Lambad将List转换成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：

遍历的时候需要使用到元素的索引，很可惜，Java8 的 Iterable 并没有提供一个带索引的 forEach 方法，自动动手写一个满足自己的需求。

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

public classIterables {public static voidforEach(