JAVA8中lamda表达式对集合的操作

一些自己整理的demo，便于回顾。

1.遍历和处理业务

List<Integer> listScore = Arrays.asList(5, 20); //遍历泛型为基本类型直接用使用接口 listScore.stream().forEach(System.out::println); //遍历自定义的类 只能先定义对象student list.stream().forEach(student -> System.out.println(student.toString())); //遍历处理多行业务 list.stream().forEach(student -> { String status = student.getScore() < 60 ? ":不合格" : ":合格"; student.setStatus(status); });

2.筛选

//筛选60以下为不不及格 用于只有一次判断 list.stream().filter(student -> (student.getScore() < 60)).forEach(s -> s.setStatus("不及格")); //把分数转化成一个新的集合 List<Integer> listScore = list.stream().map(student -> student.getScore()).collect(Collectors.toList()); //遍历泛型为基本类型直接用使用接口 listScore.stream().forEach(System.out::println); //把60分以下的转化冲一个新集合 List<Student> dStudent = list.stream().filter(student -> student.getScore() < 60).collect(Collectors.toList()); System.out.println("***不及格****"); dStudent.stream().forEach(student -> System.out.println(student.toString()));

3.合并+查找

Student stu3 = new Student("haiMianBaby", 90); Student stu4 = new Student("paiDaXing", 100); List<Student> studentList = Arrays.asList(stu3, stu4); //把两个集合汇成一个集合 List<Student> allStudent = Stream.of(list, studentList).flatMap(students -> students.stream()).collect(Collectors.toList()); allStudent.stream().forEach(student -> System.out.println(student.toString())); //寻找集合中最多对象 Student highScoreStudent = allStudent.stream().max(Comparator.comparing(student -> student.getScore())).get(); Student lowScoreStudent = allStudent.stream().min(Comparator.comparing(student -> student.getScore())).get(); System.out.println("分数最高:" + highScoreStudent.toString()); System.out.println("分数最低" + lowScoreStudent);

Student类

public class Student { private String name; private Integer score; private String status = "无"; }