Java代码：有自动售货机若投入1.5元硬币，按“可乐”“雪碧”或“红茶”按钮，送出相应的饮料；若投入的是2元硬币，在送出饮料的同时退出5角硬币。如果没有零钱则退还2元钱，且给出红灯警示。

下面是Java代码实现：

import java.util.Scanner;

public class VendingMachine {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        int selection;
        double money = 0;
        boolean hasChange = true;
        while (hasChange) {
            System.out.println("Please insert a coin (1.5 or 2):");
            double coin = input.nextDouble();
            if (coin == 1.5) {
                System.out.println("Please select a drink (1 - coke, 2 - sprite, 3 - tea):");
                selection = input.nextInt();
                if (selection == 1) {
                    System.out.println("Here is your coke.");
                } else if (selection == 2) {
                    System.out.println("Here is your sprite.");
                } else if (selection == 3) {
                    System.out.println("Here is your tea.");
                } else {
                    System.out.println("Invalid selection.");
                }
            } else if (coin == 2.0) {
                System.out.println("Please select a drink (1 - coke, 2 - sprite, 3 - tea):");
                selection = input.nextInt();
                if (selection == 1) {
                    System.out.println("Here is your coke.");
                } else if (selection == 2) {
                    System.out.println("Here is your sprite.");
                } else if (selection == 3) {
                    System.out.println("Here is your tea.");
                } else {
                    System.out.println("Invalid selection.");
                }
                System.out.println("Here is your change (0.5).");
                money += 0.5;
            } else {
                System.out.println("Invalid coin.");
            }
            if (money >= 2.0) {
                System.out.println("Sorry, no change available. Please take your money (2.0).");
                hasChange = false;
            }
        }
        System.out.println("Red light warning!");
    }
}

使用Scanner类实现用户输入硬币和饮料选择，使用if-else语句判断硬币种类和饮料选择，并输出相应的信息。使用while循环判断是否还有零钱可找，如果没有则退出循环并输出红灯警示。