函数式编程-Stream流-三更 Author、Book、测试代码

package com.sofwoin; import javafx.print.Collation; import java.util.*; import java.util.function.*; import java.util.stream.Collectors; import java.util.stream.Stream; /** * @packageName: com.sofwoin * @author: wentao * @date: 2023/11/17 20:12 * @version: 1.0 * @email [email protected] * @description: TODO */ public class Test { public static void main(String[] args) { // ctrl+alt+m 选择几行代码自动封装成方法 // test1(); // test2(); // test3(); // test4(); // test5(); // test6(); // test7(); // test8(); // test9(); // test10(); // test11(); // test12(); // test13(); // test14(); // test15(); // test16(); // test17(); // test18(); // test19(); // test20(); // test21(); // test22(); // test23(); // test24(); // test25(); // test26(); // test27(); // test28(); // test29(); test30(); } private static void test30() { List<Author> authors = getAuthors(); authors.stream() .map(author -> author.getAge()) .map(age -> age + 10) .filter(age->age>18) .map(age->age+2) .forEach(System.out::println); List<Author> authors2 = getAuthors(); authors2.stream() .mapToInt(e -> e.getAge()) .map(age -> age + 10) .filter(age->age>18) .map(age->age+2) .forEach(System.out::println); } private static void test29() { //类名::new // List<Author> authors = getAuthors(); // authors.stream() // .map(author -> author.getName()) // .map(name->new StringBuilder(name)) // .map(sb->sb.append("-三更").toString()) // .forEach(str-> System.out.println(str)); List<Author> authors = getAuthors(); authors.stream() .map(author -> author.getName()) .map(StringBuilder::new) .map(sb->sb.append("-三更").toString()) .forEach(str-> System.out.println(str)); } private static void test28() { // 类名::方法名 // subAuthorName("三更草堂", new UseString() { // @Override // public String use(String str, int start, int length) { // return str.substring(start,length); // } // }); subAuthorName("三更草堂", (str, start, length) -> str.substring(start,length)); } interface UseString{ String use(String str,int start,int length); } public static String subAuthorName(String str, UseString useString){ int start = 0; int length = 1; return useString.use(str,start,length); } private static void test27() { //对象名::方法名 List<Author> authors = getAuthors(); Stream<Author> authorStream = authors.stream(); StringBuilder sb = new StringBuilder(); // authorStream.map(author -> author.getName()) // .forEach(name->sb.append(name)); authorStream.map(author -> author.getName()) .forEach(sb::append); } private static void test26() { //类名::方法名 List<Author> authors = getAuthors(); Stream<Author> authorStream = authors.stream(); // authorStream.map(author -> author.getAge()) // .map(age->String.valueOf(age)); authorStream.map(author -> author.getAge()) .map(String::valueOf); } private static void test25() { Optional.ofNullable(null); //不会报错 // Optional.of(null); //会报错 Optional<Author> authorOptional = Optional.ofNullable(getAuthors().get(0)); Author author1 = authorOptional.orElseGet(() -> new Author()); Author author2= authorOptional.orElse(new Author()); } private static void test24() { // 使用reduce求所有作者中年龄的最小值 Optional<Integer> reduce = getAuthors().stream() .map(author -> author.getAge()) .distinct() .reduce((result, element) -> element < result ? element : result); reduce.ifPresent(System.out::println); } private static void test23() { // 使用reduce求所有作者中年龄的最小值 Integer min = getAuthors().stream() .map(author -> author.getAge()) .distinct() .reduce(Integer.MAX_VALUE, (result, element) -> element < result ? element : result); System.out.println(min); } private static void test22() { // 使用reduce求所有作者中年龄的最大值 Integer max = getAuthors().stream() .map(author -> author.getAge()) .reduce(Integer.MIN_VALUE, (result, element) -> element > result ? element : result); System.out.println(max); } private static void test21() { // 例子：使用reduce求所有作者年龄的和 Integer sum = getAuthors().stream() .map(author -> author.getAge()) .reduce(0, (integer, element) -> integer + element); System.out.println(sum); } private static void test20() { // 获取一个年龄最小的作家，并输出他的姓名。 Optional<Author> first = getAuthors().stream() .findFirst(); first.ifPresent(System.out::println); } private static void test19() { // 获取任意一个年龄大于18的作家，如果存在就输出他的名字 Optional<Author> any = getAuthors().stream() .findAny(); System.out.println(any.get()); } private static void test18() { // 判断作家是否都没有超过100岁的。 boolean flag = getAuthors().stream() .distinct() .noneMatch(author -> author.getAge() > 100); System.out.println(flag); } private static void test17() { // 判断是否所有的作家都是成年人 boolean flag = getAuthors().stream() .distinct() .allMatch(author -> author.getAge() >= 18); System.out.println(flag); } private static void test16() { // 判断是否有年龄在29以上的作家 boolean flag = getAuthors().stream() .distinct() .anyMatch(author -> author.getAge() > 29); System.out.println(flag); } private static void test15() { // 获取一个Map集合，map的key为作者名，value为List<Book> List<Author> authors = getAuthors(); Map<String, List<Book>> map = authors.stream() .distinct() .collect(Collectors.toMap(author -> author.getName(), author -> author.getBooks())); System.out.println(map); } private static void test14() { // 获取一个所有书名的Set集合。 Set<String> collect = getAuthors().stream() .flatMap(author -> author.getBooks().stream()) .map(book -> book.getName()) .collect(Collectors.toSet()); System.out.println(collect); } private static void test13() { // 获取一个存放所有作者名字的List集合。 List<String> collect = getAuthors().stream() .distinct() .map(author -> author.getName()) .col