Lambda expression
1. Implement functional interfaces and create objects (simplified writing of anonymous inner classes)
2. Syntax: interface name reference (formal parameter list)-> {//method implementation};
3.-> Left: Specify the parameters required by the Lambda expression, that is, the parameters of the method in the interface.
4.-> Right: Specify the execution function part of the lambda expression, that is, the implementation part of the method corresponding to the method in the interface.
5. For the interface implemented by the Iambda expression, only one abstract method must be defined in the interface, that is, it must be a functional interface.
