1. Stream在Java8中被定义为泛型接口
2. Stream接口代表数据流:此数据流并非我们所熟知的I/O流
3. Stream不是一个数据结构,不直接存储数据。
4. Stream通过管道操作数据。
5. 创建Stream接口实现类对象:
stream():创建一个Stream接口实现类的对象。
例如:
Stream stream = people.stream();
其中people是一个ArrayList集合,调用其中的stream()方法,返回一个Stream对象
1. 管道:代表一个操作序列。
2. 管道包含以下组件:
a. 数据集:可能是集合、数组等。
b. 零个或多个中间业务。如过滤器
c. 一个终端操作,如forEach
1. 过滤器:用给定的条件在源数据基础上过滤出新的数据,并返回一个Stream对象。
2. 过滤器包含匹配的谓词。
例如:判断p对象是否为男性的lambda表达式:
Stream stream = people.stream();
stream = stream.filter(p->p.getGender() == '男');
创建Person类:
public class Person {
public static enum Sex{
MALE,FEMALE;
}
private String name;
private Sex gender;
private int age;
private double height;
public Person() {
}
public Person(String name, Sex gender, int age, double height) {
super();
this.name = name;
this.gender = gender;
this.age = age;
this.height = height;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Sex getGender() {
return gender;
}
public void setGender(Sex gender) {
this.gender = gender;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public double getHeight() {
return height;
}
public void setHeight(double height) {
this.height = height;
}
@Override
public String toString() {
return "Person [name=" + name + ", gender=" + gender + ", age=" + age + ", height=" + height + "]";
}
}
创建一个生成元素为Person对象的ArrayList集合的静态方法:
public class Test03_collection_stream {
public static List createPerson(){
List people = new ArrayList();
Person person = new Person("张飞",Person.Sex.MALE,33,1.99);
people.add(person);
person = new Person("王菲",Person.Sex.FEMALE,33,1.65);
people.add(person);
person = new Person("刘亦菲",Person.Sex.FEMALE,33,1.68);
people.add(person);
person = new Person("李四",Person.Sex.MALE,33,1.76);
people.add(person);
person = new Person("小马",Person.Sex.MALE,33,1.71);
people.add(person);
person = new Person("郭靖",Person.Sex.MALE,33,1.88);
people.add(person);
return people;
}
}
创建一个main方法,在main方法中进行测试:
public class Test03_collection_stream {
public static void main(String[] args) {
List people = createPerson();//调用createPerson静态方法,返回一个List集合,集合中包含若干个Person对象。
Stream stream = people.stream(); //调用集合的stream()方法返回一个Stream对象
stream.forEach(p -> {
System.out.println(p);
});//调用Stream的forEach()方法,该方法传入一个lambda表达式。
}
}
运行main方法,控制台打印输出如下:
Person [name=张飞, gender=MALE, age=33, height=1.99]
Person [name=王菲, gender=FEMALE, age=33, height=1.65]
Person [name=刘亦菲, gender=FEMALE, age=33, height=1.68]
Person [name=李四, gender=MALE, age=33, height=1.76]
Person [name=小马, gender=MALE, age=33, height=1.71]
Person [name=郭靖, gender=MALE, age=33, height=1.88]
本文代码资源下载地址:
https://github.com/gitHjx/java8.git