Functional Interfaces & Lambda Expressions - Simple Application Notes

The following is an understanding based on data and experiments:
1、LambdaThe use of expressions is related to functional interfaces
2、函数式接口有且仅有一个抽象方法

函数式接口、LambdaIf you don't understand the expression, you can refer to other articles
The following code can be copied and pasted by yourself to see the execution effect

//函数式接口 There is only one method in the interface
@FunctionalInterface
public interface MyFunctionalInterface {
    
    int test(int a,int b);
}

import java.util.ArrayList;
import java.util.List;

public class testLambda {
    
    private static int sum(MyFunctionalInterface myFunctionalInterface,int a,int b){
    
        return myFunctionalInterface.test(a,b);
    }

    public static void main(String[] args) {
    
        //LambdaClassic example of expression
        List<String> list = new ArrayList<>();
        list.add("abc");
        list.add("def");
        list.add("ghi");
        list.forEach(item -> System.out.println(item));

        //Basic use of functional interfaces 基本语法: (parameters) -> expression 或 (parameters) ->{ statements; }
        MyFunctionalInterface myFunctionalInterface = (int a,int b)-> {
    
            return a+b;
        };

        //简写
        MyFunctionalInterface myFunctionalInterface1 = (int a,int b)-> a+b;
        int result = myFunctionalInterface1.test(3,2);
        System.out.println(result);

        //A typical use case for a functional interface is as a parameter to a method
        int result1 = sum((int a,int b) -> a+b,20,36);
        System.out.println(result1);
    }
}