jdk8-api练习

APIExecrise.java

package jdk8;

import org.junit.Before;
import org.junit.Test;

import java.util.Arrays;
import java.util.Comparator;
import java.util.List;
import java.util.Optional;
import java.util.stream.Collectors;

public class APIExecrise {
    List<Employee> emps = Arrays.asList(
        new Employee(101, "李四", 59, 6666.66, "busy"),
        new Employee(102, "张三", 18, 9999.99, "free"),
        new Employee(103, "王五", 28, 3333.33, "vocation"),
        new Employee(104, "赵六", 8, 7777.77, "free"),
        new Employee(105, "田七", 38, 5555.55, "busy")
    );

    List<Transaction> transactions = Arrays.asList(
            new Transaction(new Trade("Raoul", "Cambridge"), 2011, 300),
            new Transaction(new Trade("Mario", "Milan"), 2011, 400),
            new Transaction(new Trade("Alan", "Cambridge"), 2012, 710),
            new Transaction(new Trade("Brian", "Cambridge"), 2012, 950)
    );;




    /**
     * 1.给定一个数字列表，返回一个数字平方
     */
    @Test
    public void test01() {
        Integer[] nums = new Integer[]{1,2,3,4,5};

        Arrays.stream(nums)
                .map(n -> n * n)
                .forEach(System.out :: println);
    }

    /**
     * 2.用map和reduce数一数流中有多少个Employee
     */
    @Test
    public void test02() {
        emps.stream()
                .map(e -> 1)
                .reduce(Integer::sum)
                .ifPresent(System.out::println);
    }

    /**
     * 1.找出2011年发生的所有交易，按交易额从低到高排序
     */
    @Test
    public void test1() {
        transactions.stream()
                .filter(t -> t.getYear() == 2011)
                .sorted((t1, t2) -> Integer.compare(t1.getValue(), t2.getValue()))
                .forEach(System.out::println);
    }

    /**
     * 2.交易员都在哪些不同的城市工作过
     */
    @Test
    public void test2() {
        transactions.stream()
                .map(t -> t.getTrade().getCity())
                .forEach(System.out::println);
    }

    /**
     * 3.查找来自剑桥的交易员，按姓名排序
     */
    @Test
    public void test3() {
        transactions.stream()
                .filter(t -> "Cambridge".equals(t.getTrade().getCity()))
                .map(Transaction::getTrade)
                .sorted(Comparator.comparing(Trade::getName))
                .forEach(System.out::println);
    }

    /**
     * 4.返回所有交易员姓名字符串，按字母顺序排序
     */
    @Test
    public void test4() {
        transactions.stream()
                .map(t -> t.getTrade().getName())
                .sorted()
                .forEach(System.out::println);
    }

    /**
     * 5.有没有交易员在米兰工作过
     */
    @Test
    public void test5() {
        boolean b = transactions.stream()
//                .map(Transaction::getTrade)
                .anyMatch(t -> "Milan".equals(t.getTrade().getCity()));

        System.out.println(b);
    }

    /**
     * 6.打印在剑桥所有的交易额
     */
    @Test
    public void test6() {
        transactions.stream()
                .filter(t -> "Cambridge".equals(t.getTrade().getCity()))
                .map(Transaction::getValue)
                .reduce(Integer::sum)
                .ifPresent(System.out::println);
    }

    /**
     * 7.查出最高的交易额
     */
    @Test
    public void test7() {
        transactions.stream()
                .map(Transaction::getValue)
                .max(Integer::compareTo)
                .ifPresent(System.out::println);
    }

    /**
     * 8.找到交易额最小的交易
     */
    @Test
    public void test8() {
        transactions.stream()
                .min(Comparator.comparingInt(Transaction::getValue))
                .ifPresent(System.out::println);
    }








}


class Transaction {
    List<Transaction> transactions = null;

    private Trade trade;
    private int year;
    private int value;

    @Before
    public void before() {
        Trade raoul = new Trade("Raoul", "Cambridge");
        Trade mario = new Trade("Mario", "Milan");
        Trade alan = new Trade("Alan", "Cambridge");
        Trade brian = new Trade("Brian", "Cambridge");

        transactions = Arrays.asList(
                new Transaction(brian, 2011, 300),
                new Transaction(raoul, 2011, 400),
                new Transaction(mario, 2012, 710),
                new Transaction(alan, 2012, 950)
        );


    }


    public Transaction(Trade trade, int year, int value) {
        this.trade = trade;
        this.year = year;
        this.value = value;
    }

    public Transaction() {
    }

    public Trade getTrade() {
        return trade;
    }

    public void setTrade(Trade trade) {
        this.trade = trade;
    }

    public int getYear() {
        return year;
    }

    public void setYear(int year) {
        this.year = year;
    }

    public int getValue() {
        return value;
    }

    public void setValue(int value) {
        this.value = value;
    }

    @Override
    public String toString() {
        return "Transaction{" +
                "trade=" + trade +
                ", year=" + year +
                ", value=" + value +
                '}';
    }
}

class Trade {
    private String name;
    private String city;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getCity() {
        return city;
    }

    public void setCity(String city) {
        this.city = city;
    }

    public Trade(String name, String city) {
        this.name = name;
        this.city = city;
    }

    public Trade() {
    }

    @Override
    public String toString() {
        return "Trade{" +
                "name='" + name + '\'' +
                ", city='" + city + '\'' +
                '}';
    }
}



class Employee {
    private int id;
    private String name;
    private int age;
    private double salary;
    private String status;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public double getSalary() {
        return salary;
    }

    public void setSalary(double salary) {
        this.salary = salary;
    }

    public String getStatus() {
        return status;
    }

    public void setStatus(String status) {
        this.status = status;
    }

    Employee(int id, String name, int age, double salary, String status) {
        this.id = id;
        this.name = name;
        this.age = age;
        this.salary = salary;
        this.status = status;
    }

    public Employee() {
    }
}