Java 8供应商示例

男娘i 2023-02-15 05:07 84阅读 0赞

在Java 8中， [供应商][Link 1]是一个功能接口； 它不带任何参数并返回结果。

Supplier.java

@FunctionalInterface
    public interface Supplier<T> {
        T get();
    }

## 1.供应商 ##

1.1此示例使用`Supplier`返回当前日期时间。

Java8Supplier1.java

package com.mkyong;
    
    import java.time.LocalDateTime;
    import java.time.format.DateTimeFormatter;
    import java.util.function.Supplier;
    
    public class Java8Supplier1 {
    
        private static final DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
    
        public static void main(String[] args) {
    
            Supplier<LocalDateTime> s = () -> LocalDateTime.now();
            LocalDateTime time = s.get();
    
            System.out.println(time);
    
            Supplier<String> s1 = () -> dtf.format(LocalDateTime.now());
            String time2 = s1.get();
    
            System.out.println(time2);
    
        }
    
    }

输出量

2020-03-02T16:10:49.281223
    2020-03-02 16:10:49

## 2.退还供应商 ##

Java8Supplier2.java

package com.mkyong;
    
    import java.util.ArrayList;
    import java.util.List;
    import java.util.function.Supplier;
    
    public class Java8Supplier2<T> {
    
        public static void main(String[] args) {
    
            Java8Supplier2<String> obj = new Java8Supplier2();
    
            List<String> list = obj.supplier().get();
    
        }
    
        public Supplier<List<T>> supplier() {
    
            // lambda
            // return () -> new ArrayList<>();
    
            // constructor reference
            return ArrayList::new;
    
        }
    
    }

## 3.工厂 ##

3.1一个简单的工厂方法来返回`Developer`对象。

Java8Supplier3.java

package com.mkyong;
    
    import java.math.BigDecimal;
    import java.time.LocalDate;
    import java.util.function.Supplier;
    
    public class Java8Supplier3 {
    
        public static void main(String[] args) {
    
            Developer obj = factory(Developer::new);
            System.out.println(obj);
    
            Developer obj2 = factory(() -> new Developer("mkyong"));
            System.out.println(obj2);
    
        }
    
        public static Developer factory(Supplier<? extends Developer> s) {
    
            Developer developer = s.get();
            if (developer.getName() == null || "".equals(developer.getName())) {
                developer.setName("default");
            }
            developer.setSalary(BigDecimal.ONE);
            developer.setStart(LocalDate.of(2017, 8, 8));
    
            return developer;
    
        }
    
    }

Developer.java

package com.mkyong;
    
    import java.math.BigDecimal;
    import java.time.LocalDate;
    
    public class Developer {
    
        String name;
        BigDecimal salary;
        LocalDate start;
    
        // for factory(Developer::new);
        public Developer() {
        }
    
        // for factory(() -> new Developer("mkyong"));
        public Developer(String name) {
            this.name = name;
        }
    
        // get, set, constructor, toString
        //...
    
    }

输出量

Developer{name='default', salary=1, start=2017-08-08}
    Developer{name='mkyong', salary=1, start=2017-08-08}

## 参考文献 ##

*  [供应商][Link 1]
 *  Java 8 –如何格式化LocalDateTime
 *  [DateTimeFormatter JavaDoc][]
 *  Java 8教程

标签： [工厂][Link 2] [功能接口][Link 3] [Java 8][] [供应商][Link 4]

> 翻译自: [https://mkyong.com/java8/java-8-supplier-examples/][https_mkyong.com_java8_java-8-supplier-examples]

[Link 1]: https://docs.oracle.com/javase/8/docs/api/java/util/function/Supplier.html
[DateTimeFormatter JavaDoc]: https://docs.oracle.com/javase/8/docs/api/java/time/format/DateTimeFormatter.html
[Link 2]: https://mkyong.com/tag/factory/
[Link 3]: https://mkyong.com/tag/functional-interface/
[Java 8]: https://mkyong.com/tag/java-8/
[Link 4]: https://mkyong.com/tag/supplier/
[https_mkyong.com_java8_java-8-supplier-examples]: https://mkyong.com/java8/java-8-supplier-examples/