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其工作原理或解释以下代码示例：

@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 Java8 中支持 Lambda 表达式。

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

此方法的简单示例

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());
        };
    }
}

需要帮助理解 Java 中的符号“->”

Need help understanding symbol "->" in Java

java

symbols