需要帮助理解 Java 中的符号“->”

Question

需要帮助理解 Java 中的符号 ->。 Google 和 Stack Overflow 搜索均未返回任何结果。有人可以分享一些链接以了解它是如何工作的或解释下面的代码示例：

@SpringBootApplication
public class Application {

    @Bean
    CommandLineRunner commandLineRunner(PersonRepository personRepository) {
        return args -> {
            Arrays.asList("Phil", "Josh").forEach(name ->
                personRepository.save(new Person(name, (name + "@email.com").toLowerCase()))
            );
            personRepository.findAll().forEach(System.out::println);
        };
    }

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

Answer 1

在 Java 8 中支持 Lambda 表达式。

一个 lambda 表达式具有以下语法特征。

            parameter -> expression body.

考虑以下示例

   //with type declaration
  MathOperation addition = (int a, int b) -> a + b;

  //with out type declaration
  MathOperation subtraction = (a, b) -> a - b;

  //with return statement along with curly braces
  MathOperation multiplication = (int a, int b) -> { return a * b; };
  //without return statement and without curly braces
  MathOperation division = (int a, int b) -> a / b;

  System.out.println("10 + 5 = " + tester.operate(10, 5, addition));       
  System.out.println("10 - 5 = " + tester.operate(10, 5, subtraction));
  System.out.println("10 x 5 = " + tester.operate(10, 5, multiplication));
  System.out.println("10 / 5 = " + tester.operate(10, 5, division));

参考Lamba expressions Java8

Answer 2

这种方法的简单示例

public class Main {

    @FunctionalInterface
    interface NiceInterface {
        void run(String[] args);
    }

    public static void main(String[] args) {

        NiceInterface myNice = myArgs -> {
            for (String myArg : myArgs) {
                System.out.println(myArg);
            }
        };

        myNice.run(new String[]{"aaa", "bbb"});
        //aaa
        //bbb

        myNice = getOtherNice();

        myNice.run(new String[]{"111", "222", "333"});
        //111222333
    }

    private static NiceInterface getOtherNice() {
        return args -> {
            StringBuilder sb = new StringBuilder();
            for (String myArg : args) {
                sb.append(myArg);
            }

            System.out.println(sb.toString());
        };
    }
}