public interface Consumer<T> {

    /**
     * Performs this operation on the given argument.
     *
     * @param t the input argument
     */
    void accept(T t);

    /**
     * Returns a composed {@code Consumer} that performs, in sequence, this
     * operation followed by the {@code after} operation. If performing either
     * operation throws an exception, it is relayed to the caller of the
     * composed operation.  If performing this operation throws an exception,
     * the {@code after} operation will not be performed.
     *
     * @param after the operation to perform after this operation
     * @return a composed {@code Consumer} that performs in sequence this
     * operation followed by the {@code after} operation
     * @throws NullPointerException if {@code after} is null
     */
    default Consumer<T> andThen(Consumer<? super T> after) {
        Objects.requireNonNull(after);
        return (T t) -> { accept(t); after.accept(t); };
    }
}

public static void main(String[] args) {
    //现在我们想新建一个线程来搞事情
    Thread thread = new Thread(new Runnable() {   
        //创建一个实现Runnable的匿名内部类
        @Override
        public void run() {   //具体的实现逻辑
            System.out.println("Hello World!");
        }
    });
    thread.start();
}

public static void main(String[] args) {
    // String a = "Hello World!";   之前我们定义变量必须指定类型
    var a = "Hello World!";   //现在我们使用var关键字来自动进行类型推断，因为完全可以从后面的值来判断是什么类型
}