Java8 stream基础

Posted 2020-11-03 东方旭日,笑傲江湖

List<Integer> list = new ArrayList<Integer>();
list.add(2);
list.add(4);
list.add(0);
list.add(100);
System.out.println("----------------stream---------------------");
list.stream().filter(e -> e > 4).forEach(System.out::println);
Stream<Integer> list1 = list.stream().filter(e -> e > 0);
Iterator<Integer> iter = list1.iterator();
while (iter.hasNext()) {
System.out.println(iter.next());
}
System.out.println("--------------filter 条件查询--------------------");
list = list.stream().filter(e -> e > 2).collect(Collectors.toList());
list.forEach(System.out::println);
List<Student> studentlist=new ArrayList<Student>();
studentlist.add(new Student("A",12));
studentlist.add(new Student("B",5));
studentlist.add(new Student("C",16));
studentlist.add(new Student("D",2));
System.out.println("取出集合中对象指定属性");
studentlist.stream().map(Student::getName).forEach(System.out::println);
System.out.println("-----------------------------按对象属性正序---------------------------------------------");
studentlist.stream().sorted(Comparator.comparing(Student::getAge)).forEach(System.out::println);
System.out.println("-----------------------------按对象属性倒序---------------------------------------------");
studentlist.stream().sorted(Comparator.comparing(Student::getAge).reversed()).forEach(System.out::println);
studentlist=studentlist.stream().sorted(Comparator.comparing(Student::getAge).reversed()).collect(Collectors.toList());
System.out.println("----------------------------stream 转化为集合输出----------------------------------------------");
studentlist.forEach(System.out::print);

class Student{
private String name;
private Integer age;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
public Student(String name, Integer age) {
super();
this.name = name;
this.age = age;
}
public Student() {
super();
}
@Override
public String toString() {
return "Student [name=" + name + ", age=" + age + "]";
}


}