Java 8 Supplier 使用

在Java 8, Supplier是一个函数接口,它没有参数,返回了一个T.查了下字典,supplier被翻译成"供应商",那么它到底供应了啥呢,从代码上看,就是供应了一个任意对象T呗，下面我们去看看几个DEMO吧.

思考: 写JDK代码的大神们,为什么取名叫Supplier?为啥不叫Vendor或者Provider呢...我想了很久.

package java.util.function;

@FunctionalInterface

public interface Supplier {

T get();

}

1、使用Supplier打印字符串

package com.cattles.function;

import java.time.LocalDateTime;

import java.time.format.DateTimeFormatter;

import java.util.function.Supplier;

/**

* @author cattle - 稻草鸟人

* @date 2020/3/22 下午12:56

*/

public class Java8Supplier1 {

private static final DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");

public static void main(String[] args) {

// print simple string

Supplier supplier = () -> "cattle";

System.out.println(supplier.get());

// print date time

Supplier time = () -> LocalDateTime.now();

System.out.println(time.get());

Supplier s = () -> dtf.format(time.get());

System.out.println(s.get());

}

}

输出:

cattle

2020-03-22T13:45:53.926364

2020-03-22 13:45:53

2、返回一个Supplier

下面我们创建一个简单的工厂方法返回一个Developer 对象

package com.cattles.function;

import java.math.BigDecimal;

import java.util.ArrayList;

import java.util.List;

import java.util.Optional;

import java.util.function.Supplier;

/**

* @author cattle - 稻草鸟人

* @date 2020/3/22 下午12:56

*/

public class Java8Supplier3 {

public static void main(String[] args) {

Developer developer = factory(Developer::new);

System.out.println(developer);

Developer developer1 = factory(()-> new Developer("tony"));

System.out.println(developer1);

}

public static Developer factory(Supplier extends Developer> supplier) {

Developer developer = supplier.get();

if(Optional.ofNullable(developer.getName()).isEmpty()) {

developer.setName("cattle");

}

//可怜的人啊,薪水是zero

developer.setSalary(BigDecimal.ZERO);

//没日没夜干活的码农啊

developer.setTitle("Coder");

return developer;

}

static class Developer {

/**

* 姓名

*/

private String name;

/**

* 职位

*/

private String title;

/**

* 薪水

*/

private BigDecimal salary;

public Developer(String name) {

this.name = name;

}

// 省略 gettter setter toString 方法

}

}

看看结果:

Developer{name='cattle', title='Coder', salary=0}

Developer{name='tony', title='Coder', salary=0}