Java8-Guava实战示例

示例一：

跟示例三对比一下，尽量用示例三

List<InvoiceQueryBean> invoiceQueryBeanList = new ArrayList<>();
List<String> invoices = Lists.newArrayList(Iterators.transform(invoiceQueryBeanList.iterator(), new Function<InvoiceQueryBean, String>() {@Nullable@Overridepublic String apply(@Nullable InvoiceQueryBean input) {if (StringUtils.isNotBlank(input.getLoanInvoiceId())) {return input.getLoanInvoiceId();} else {return null;}}
}));
//去除空的
Iterators.removeIf(invoices.iterator(), StringUtils::isBlank);

示例二：

public static List<PersonLoanInvoiceQueryPojo> getInvoiceQueryPojoList(List<InvoiceQueryBean> invoiceQueryBean) {return Lists.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 implements Serializable{private static final long serialVersionUID = -408985049449365784L;private String loanInvoiceId;private String userId;private String userName;public static class Builder {private PersonLoanInvoiceQueryPojo instance = new PersonLoanInvoiceQueryPojo();private Builder(){}public static Builder getInstance() {return new Builder();}public static Builder getInstance(PersonLoanInvoiceQueryPojo instance){Builder builder = new Builder();builder.instance = instance;return builder;}public Builder addLoanInvoiceId(String loanInvoiceId) {this.instance.setLoanInvoiceId(loanInvoiceId);return this;}public Builder addUserId(String userId) {this.instance.setUserId(userId);return this;}public Builder addUserName(String userName) {this.instance.setUserName(userName);return this;}public PersonLoanInvoiceQueryPojo 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）

import com.google.common.collect.Iterators;
import com.google.common.collect.Lists;List<CreditPersonalInfoChangeApplySerial> applySerialList = new ArrayList<>();
List<String> 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

import com.google.common.collect.Maps;List<QueryUserAppInfoByUserIdListPojo> operatorInfoList = new ArrayList<>();
Map<String, QueryUserAppInfoByUserIdListPojo> operatorMap= Maps.uniqueIndex(operatorInfoList.iterator(), QueryUserAppInfoByUserIdListPojo::getUserId);public class QueryUserAppInfoByUserIdListPojo implements Serializable {private static final long serialVersionUID = 6876288995978264269L;private String userId;public String getUserId() {return this.userId;}public void setUserId(String userId) {this.userId = userId;}}

 示例五：

List<UserPojo> 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。

import java.util.Objects;
import java.util.function.BiConsumer;/*** Iterable 的工具类*/
public class Iterables {public static <E> void forEach(Iterable<? extends E> elements, BiConsumer<Integer, ? super E> action) {Objects.requireNonNull(elements);Objects.requireNonNull(action);int index = 0;for (E element : elements) {action.accept(index++, element);}}
}

 

public static void main(String[] args) throws Exception {List<String> 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()函数有两个重载方法，其中一个是带 defaultValue 的，注意如果别迭代的集合没有符合条件的数据的话，一定要定义一个默认值。否则会报NoSuchElementException异常

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

 

参考：