JAVA基础-枚举类型和Lamda表达式

public class Test {
public static void main(String args[]){
Test tester = new Test();

  // 类型声明
  MathOperation addition = (int a, int b) -> a + b;
    
  // 不用类型声明
  MathOperation subtraction = (a, b) -> a - b;
    
  // 大括号中的返回语句
  MathOperation multiplication = (int a, int b) -> { return a * b; };
    
  // 没有大括号及返回语句
  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));
  
  // 不用括号
  GreetingService greetService1 = message ->
  System.out.println("Hello " + message);
    
  // 用括号
  GreetingService greetService2 = (message) ->
  System.out.println("Hello " + message);
    
  greetService1.sayMessage("Baidu");
  greetService2.sayMessage("Google");

}

interface MathOperation {
int operation(int a, int b);
}

interface GreetingService {
void sayMessage(String message);
}

private int operate(int a, int b, MathOperation mathOperation){
return mathOperation.operation(a, b);
}
}

// 输出：
// 10 + 5 = 15
// 10 - 5 = 5
// 10 x 5 = 50
// 10 / 5 = 2
// Hello Baidu
// Hello Google