Getting Started with Java Lambda Expressions: Implementing Simple Functional Interfaces in One Line of Code

Java 8 introduced Lambda expressions to address the problem of code redundancy in anonymous inner classes when dealing with single abstract method interfaces such as `Runnable` and `Comparator`. A functional interface is an interface that contains exactly one abstract method, which is a prerequisite for using Lambda expressions. The core syntax of a Lambda expression is "parameter list -> expression body": empty parameters use `()`, a single parameter can omit the parentheses, multiple parameters are enclosed in `()`, and the types are automatically inferred by the compiler; single-line expressions can omit `{}`, while multi-line expressions require `{}` and an explicit `return`. Through examples: Starting a thread can be simplified to `new Thread(() -> System.out.println("Thread started"))`; sorting a collection uses `Collections.sort(list, (a, b) -> a.length() - b.length())`; a custom interface `Calculator` can be implemented as `(a, b) -> a + b`. Lambda expressions make code more concise, reduce template code, and improve readability. When combined with subsequent features like the `Stream API`, further optimizations in efficiency can be achieved.