JAVA lambda 简单例子

多了不说直接上代码

package com.example.demo;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.IntSummaryStatistics;
import java.util.List;
import java.util.Set;
import java.util.TreeSet;
import java.util.function.Consumer;
import java.util.function.Predicate;
import java.util.stream.Collectors;

public class Test {

public static void main(String[] args) {
       List<Person> javaProgrammers = new ArrayList<Person>() {
           private static final long serialVersionUID = 1L;
           {
               add(new Person("Elsdon", "Jaycob", "Java programmer", "male",
                       43, 2000));
               add(new Person("Tamsen", "Brittany", "Java programmer",
                       "female", 23, 1500));
               add(new Person("Floyd", "Donny", "Java programmer", "male", 33,
                       1800));
               add(new Person("Sindy", "Jonie", "Java programmer", "female",
                       32, 1600));
               add(new Person("Vere", "Hervey", "Java programmer", "male", 22,
                       1200));
               add(new Person("Maude", "Jaimie", "Java programmer", "female",
                       27, 1900));
               add(new Person("Shawn", "Randall", "Java programmer", "male",
                       30, 2300));
               add(new Person("Jayden", "Corrina", "Java programmer", "female",
                       35, 1700));
               add(new Person("Palmer", "Dene", "Java programmer", "male", 33,
                       2000));
               add(new Person("Addison", "Pam", "Java programmer", "female",
                       34, 1300));
           }
       };
       List<Person> phpProgrammers = new ArrayList<Person>() {
           private static final long serialVersionUID = 1L;
           {
               int i = 0;
               while (i < 100) {
                   add(new Person("Jarrod_" + i, "Pace", "PHP programmer",
                           "male", 34, 1550));
                   i++;
               }
               add(new Person("Jarrod", "Pace", "PHP programmer", "male", 34,
                       1550));
               add(new Person("Clarette", "Cicely", "PHP programmer", "female",
                       23, 1200));
               add(new Person("Victor", "Channing", "PHP programmer", "male",
                       32, 1600));
               add(new Person("Tori", "Sheryl", "PHP programmer", "female", 21,
                       1000));
               add(new Person("Osborne", "Shad", "PHP programmer", "male", 32,
                       1100));
               add(new Person("Rosalind", "Layla", "PHP programmer", "female",
                       25, 1300));
               add(new Person("Fraser", "Hewie", "PHP programmer", "male", 36,
                       1100));
               add(new Person("Quinn", "Tamara", "PHP programmer", "female",
                       21, 1000));
               add(new Person("Alvin", "Lance", "PHP programmer", "male", 38,
                       1600));
               add(new Person("Evonne", "Shari", "PHP programmer", "female",
                       40, 1800));
           }
       };
       System.out.println("所有程序员的姓名:");
       javaProgrammers.forEach((p) -> System.out.printf("%s %s; ",
               p.getFirstName(), p.getLastName()));
       phpProgrammers.forEach((p) -> System.out.printf("%s %s; ",
               p.getFirstName(), p.getLastName()));

System.out.println("给程序员加薪 5% :");
Consumer<Person> giveRaise = e -> e
.setSalary(e.getSalary() / 100 * 5 + e.getSalary());

javaProgrammers.forEach(giveRaise.andThen(e -> System.out.println(e)));
phpProgrammers.forEach(giveRaise.andThen(e -> System.out.println(e)));

// filters
       System.out.println("下面是月薪超过 $1,400 的PHP程序员:");
       phpProgrammers.stream().filter((p) -> (p.getSalary() > 1400))
               .forEach((p) -> System.out.printf("%s %s; ", p.getFirstName(),
                       p.getLastName()));

// filters
       Predicate<Person> ageFilter = (p) -> (p.getAge() > 25);
       Predicate<Person> salaryFilter = (p) -> (p.getSalary() > 1400);
       Predicate<Person> genderFilter = (
               p) -> ("female".equals(p.getGender()));

System.out.println("下面是年龄大于 24岁且月薪在$1,400以上的女PHP程序员:");
       phpProgrammers.stream().filter(ageFilter).filter(salaryFilter)
               .filter(genderFilter).forEach((p) -> System.out
                       .printf("%s %s; ", p.getFirstName(), p.getLastName()));

// filters
       System.out.println("年龄大于 24岁的女性 Java programmers:");
       javaProgrammers.stream().filter(ageFilter).filter(genderFilter)
               .forEach((p) -> System.out.printf("%s %s; ", p.getFirstName(),
                       p.getLastName()));
       // limit
       System.out.println("最前面的3个 Java programmers:");
       javaProgrammers.stream().limit(3).forEach((p) -> System.out
               .printf("%s %s; ", p.getFirstName(), p.getLastName()));

System.out.println("最前面的3个女性 Java programmers:");
       javaProgrammers.stream().filter(genderFilter).limit(3)
               .forEach((p) -> System.out.printf("%s %s; ", p.getFirstName(),
                       p.getLastName()));

// sorted
       System.out.println("根据 name 排序,并显示前5个 Java programmers:");
       List<Person> sortedJavaProgrammers = javaProgrammers.stream().sorted(
               (p, p2) -> (p.getFirstName().compareTo(p2.getFirstName())))
               .limit(5).collect(Collectors.toList());

sortedJavaProgrammers.forEach((p) -> System.out.printf("%s %s; %n",
p.getFirstName(), p.getLastName()));

// Collectors.toList
       System.out.println("根据 salary 排序 Java programmers:");
       sortedJavaProgrammers = javaProgrammers.stream()
               .sorted((p, p2) -> (p.getSalary() - p2.getSalary()))
               .collect(Collectors.toList());

sortedJavaProgrammers.forEach((p) -> System.out.printf("%s %s; %n",
p.getFirstName(), p.getLastName()));

// min
       System.out.println("工资最低的 Java programmer:");
       Person pers = javaProgrammers.stream()
               .min((p1, p2) -> (p1.getSalary() - p2.getSalary())).get();

System.out.printf("Name: %s %s; Salary: $%,d.", pers.getFirstName(),
pers.getLastName(), pers.getSalary());

// max
       System.out.println("工资最高的 Java programmer:");
       Person person = javaProgrammers.stream()
               .max((p, p2) -> (p.getSalary() - p2.getSalary())).get();

System.out.printf("Name: %s %s; Salary: $%,d.", person.getFirstName(),
person.getLastName(), person.getSalary());

// Collectors.joining
       System.out.println("将 PHP programmers 的 first name 拼接成字符串:");
       String phpDevelopers = phpProgrammers.stream().map(Person::getFirstName)
               .collect(Collectors.joining(" ; ")); // 在进一步的操作中可以作为标记(token)

// Collectors.toSet
       System.out.println("将 Java programmers 的 first name 存放到 Set:");
       Set<String> javaDevFirstName = javaProgrammers.stream()
               .map(Person::getFirstName).collect(Collectors.toSet());

// Collectors.toCollection
       System.out.println("将 Java programmers 的 first name 存放到 TreeSet:");
       TreeSet<String> javaDevLastName = javaProgrammers.stream()
               .map(Person::getLastName)
               .collect(Collectors.toCollection(TreeSet::new));

// parallelStream
       System.out.println("计算付给 Java programmers 的所有money:");
       int totalSalary = javaProgrammers.parallelStream()
               .mapToInt(p -> p.getSalary()).sum();

// 计算 count, min, max, sum, and average for numbers
       List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
       IntSummaryStatistics stats = numbers.stream().mapToInt((x) -> x)
               .summaryStatistics();

System.out.println("List中最大的数字 : " + stats.getMax());
       System.out.println("List中最小的数字 : " + stats.getMin());
       System.out.println("所有数字的总和 : " + stats.getSum());
       System.out.println("所有数字的平均值 : " + stats.getAverage());
   }

public static class Person {

private String firstName, lastName, job, gender;
private int salary, age;

public Person(String firstName, String lastName, String job,
               String gender, int age, int salary) {
           this.firstName = firstName;
           this.lastName = lastName;
           this.gender = gender;
           this.age = age;
           this.job = job;
           this.salary = salary;
       }

public String getFirstName() {
return firstName;
}

public void setFirstName(String firstName) {
this.firstName = firstName;
}

public String getLastName() {
return lastName;
}

public void setLastName(String lastName) {
this.lastName = lastName;
}

public String getJob() {
return job;
}

public void setJob(String job) {
this.job = job;
}

public String getGender() {
return gender;
}

public void setGender(String gender) {
this.gender = gender;
}

public int getSalary() {
return salary;
}

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

public int getAge() {
return age;
}

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

@Override
       public String toString() {
           return "Person [firstName=" + firstName + ", lastName=" + lastName
                   + ", job=" + job + ", gender=" + gender + ", salary="
                   + salary + ", age=" + age + "]";
       }

}
}

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