文章对应Scala Version : 2.12.6
博文比较偏向于实践,理论部分大家自行谷歌好了。
关于Scala:百度是这么描述的,Scala是一门多范式的编程语言,一种类似java的编程语言 [1] ,设计初衷是实现可伸缩的语言 [2] 、并集成面向对象编程和函数式编程的各种特性。
关于面向对象编程,相信很多涉及到JAVA编程的小伙伴已经很熟悉了。JAVA对于函数式编程的概念也在JAVA8开始实行起来,我们可以通过JDK8中的StrameAPI与Lambda表达式实现函数式编程,让代码变得更加高效简洁。
下面简单举两个JDK8中函数编程的栗子:
package com.java8;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.Getter;
import lombok.NoArgsConstructor;
import org.apache.commons.lang3.builder.ReflectionToStringBuilder;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.stream.Stream;
/**
* @Description:
* @Author mengfanzhu
* @Date 7/23/18 15:55
* @Version 1.0
*/
@Data
@NoArgsConstructor
@AllArgsConstructor
class UserModel{
private Long id;
private String userName;
public String toString(){
return ReflectionToStringBuilder.toString(this);
}
}
public class Test {
public static void main(String[] args) {
List<UserModel> userModels = jdk8ForEach();
jdk8mate(userModels);
jdk8Filter();
System.out.println(StateEnum.getEnum(1));
}
private static void jdk8Filter() {
System.out.println("===========JDK 8 Filter 筛选=============");
//JDK 8 filter
Integer[] its = new Integer[]{null,1,2,193893,null,144,11134};
Arrays.stream(its).filter(integer -> integer !=null).forEach(integer -> {
System.out.println(integer);
});
}
private static void jdk8mate(List<UserModel> userModels) {
System.out.println("===========JDK 8 forEach 遍历 匹配数据是否包含3的倍数=============");
System.out.println(userModels.stream().anyMatch(userModel -> userModel.getId()%3==0));
}
private static List<UserModel> jdk8ForEach() {
List<UserModel> userModels = new ArrayList<>(10);
for(Long i = 0L;i < 10L; i ++){
UserModel userModel = new UserModel();
userModel.setId(i);
userModel.setUserName("Scala"+i);
userModels.add(userModel);
}
System.out.println("===========JDK 8 forEach 遍历=============");
//JDK8 forEach
userModels.forEach(userModel -> {
System.out.println(userModel);
} );
return userModels;
}
}
@Getter
@NoArgsConstructor
@AllArgsConstructor
enum StateEnum{
A(1,"A"),
B(2,"B"),
C(3,"C");
private Integer code;
private String value;
public String toString(){
return ReflectionToStringBuilder.toString(this);
}
public static StateEnum getEnum(Integer code) {
return Stream.of(StateEnum.values()).filter(e ->e.getCode().equals(code)).findFirst().orElse(null);
}
}
熟悉JDK的同学就很嗨了,是不是减少了很多代码量。。:)