Supplier JAVA_Java 8 Supplier 使用
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}
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}