Stream流练习

package com.example.yj.practice;

import java.util.*;
import java.util.stream.Collectors;
import java.util.stream.Stream;

import com.example.yj.entity.Employees;
import com.example.yj.entity.Trader;
import com.example.yj.entity.Transaction;
import org.junit.Test;

/**

• 作者:果果

• 时间:2022/5/31 10:04
  /
  public class MyPracticeApi {
  /
  1.给定一组数字,返回由每个数字平方构成的列表
  ,给定[1,2,3,4,5] 应该返回 [1,4,9,16,25]
  */

  Trader raoul = new Trader("Raoul", "Cambridge");
  Trader mario = new Trader("Mario", "Milan");
  Trader alan = new Trader("Alan", "Cambridge");
  Trader brian = new Trader("Brian", "Cambridge");
  List transactions = Arrays.asList(
  new Transaction(brian, 2011, 300),
  new Transaction(raoul, 2012, 1000),
  new Transaction(raoul, 2011, 400),
  new Transaction(mario, 2012, 710),
  new Transaction(mario, 2012, 700),
  new Transaction(alan, 2012, 950)
  );

  @Test
  public void test01() {
  List integers = Arrays.asList(1, 2, 3, 4, 5);
  List collect = integers.stream()
  .map(x -> x * x)
  .collect(Collectors.toList());
  System.out.println(collect);
  }

  /*
  2.咋样用Map 和 reduce 方法数一数流中 有多少个Employee呢?
  */
  @Test
  public void test02() {
  List employees = Arrays.asList(
  new Employees("马海超", "18", "13797706270", Employees.Status.FREE),
  new Employees("刘振宇", "21", "18571456081", Employees.Status.FREE),
  new Employees("吴建刚", "31", "13477300996", Employees.Status.FREE),
  new Employees("刘振宇", "31", "13477300996", Employees.Status.FREE),
  new Employees("刘振宇", "31", "13477300996", Employees.Status.FREE),
  new Employees("刘振宇", "31", "13477300996", Employees.Status.FREE)
  );
  Optional reduce = employees.stream()
  .map((x) -> 1)
  .reduce(Integer::sum);
  System.out.println(reduce.get());

  }

  //1.找出2011年发生的所有交易，并按交易额排序(从低到高)
  @Test
  public void test03() {
  transactions.stream()
  .filter((x) -> x.getYear() == 2011)
  .sorted((x, y) -> Integer.compare(x.getMoney(), y.getMoney()))
  .forEach(System.out::println);

  }

  //2.交易员都在哪些不同的城市工作过?
  @Test
  public void test04() {
  transactions.stream()
  .map((x) -> x.getTrader().getCity())
  .distinct()
  .forEach(System.out::println);
  }

  //3.查找所有来自剑桥的交易员，并按姓名排序
  @Test
  public void test05(){
  transactions.stream()
  .filter((x) -> x.getTrader().getCity().equals("Cambridge"))
  .map(Transaction::getTrader)
  .sorted((t1,t2) -> t1.getName().compareTo(t2.getName()))
  .distinct()
  .forEach(System.out::println);
  }

  //4.返回所有交易员的姓名字符串，按字母顺序排序
  @Test
  public void test06(){
  transactions.stream()
  .map((x) -> x.getTrader().getName())
  .flatMap(MyPracticeApi::getChar)
  .sorted((x1,x2) -> x1.compareToIgnoreCase(x2))
  .forEach(System.out::print);

  }
  public static Stream getChar(String str){
  ArrayList list = new ArrayList<>();
  for(Character c:str.toCharArray()){
  list.add(c.toString());
  }
  return list.stream();
  }

  //5.有没有交易员是在米兰工作的?
  @Test
  public void test07(){
  boolean milan = transactions.stream()
  .anyMatch((x) -> x.getTrader().getCity().equals("Milan"));
  System.out.println(milan);

  }

  //6.打印生活在剑桥的交易员的所有交易额
  @Test
  public void test08(){
  Optional cambridge = transactions.stream()
  .filter((x) -> x.getTrader().getCity().equals("Cambridge"))
  .map(Transaction::getMoney)
  .reduce(Integer::sum);
  System.out.println(cambridge.get());
  }

  //7.所有交易中，最高的交易额是多少
  @Test
  public void test09_1(){
  Optional max = transactions.stream()
  .map((x) -> x.getMoney())
  .max(Integer::compare);
  System.out.println(max.get());
  }

  //8.找到交易额最小的交易
  @Test
  public void test10(){
  Optional min = transactions.stream()
  .min((x, y) -> Integer.compare(x.getMoney(), x.getMoney()));
  System.out.println(min.get());

  }
  }