Java：使用供应商在运行时传递值

Question

OO: dependent class needs information from grandparent class

中描述了我要解决的问题

 import java.util.function.Supplier;

 public class SupplyMe {

     private Supplier<String> supplied;

     public SupplyMe(Supplier<String> supplied) {
         this.supplied = supplied;
     }

     public void printSupplied() {
         System.out.println(supplied.get());
     }

     public static void main(String[] args) {

         String changingStr = "hi";
         Supplier<String> helloStrSupplier = () -> changingStr;

         SupplyMe mySupplyMe = new SupplyMe(helloStrSupplier);

         mySupplyMe.printSupplied();

         changingStr = "hi2";
         mySupplyMe.printSupplied();

     }
 }

以下代码抛出

SupplyMe.java:18: error: local variables referenced from a lambda expression must be final or effectively final
        Supplier<String> helloStrSupplier = () -> changingStr;

我该怎么做才能使供应商能够在运行时补充价值？

Answer 1

我能够做到这一点

import java.util.function.Supplier;

 public class SupplyMe {

     public static String changingStr = "";
     private Supplier<String> supplied;

     public SupplyMe(Supplier<String> supplied) {
         this.supplied = supplied;
     }

     public void printSupplied() {
         System.out.println(supplied.get());
     }

     public static void main(String[] args) {

         changingStr = "hi";
         //Supplier<String> helloStrSupplier = changingStr;
         Supplier<String> helloStrSupplier = new DynamicSupplier();

         SupplyMe mySupplyMe = new SupplyMe(helloStrSupplier);


         mySupplyMe.printSupplied();


         changingStr = "hi2";
         mySupplyMe.printSupplied();

     }

     static class DynamicSupplier implements Supplier<String> {
         @Override
         public String get() {
             return changingStr;
         }
     }
 }