(JAVA) Is there a more efficient way to do this?

This part of my program asks the user to enter the number of drinks they want and it must return "Invalid amount" if the number of drinks is negative.

System.out.print("Please enter the number of each drink that you like to purchase:");
System.out.println();
        
System.out.print("Small Coffee: ");
int smallCoffee = scnr.nextInt();
if (smallCoffee < 0) {
    System.out.println("Invalid amount")
    System.exit(1);
}
System.out.print("Medium Coffee: ");
int mediumCoffee = scnr.nextInt();
        
System.out.print("Large Coffee: ");
int largeCoffee = scnr.nextInt();
        
System.out.print("Banana Berry Smoothie: ");
int berrySmoothie = scnr.nextInt();
        
System.out.print("Mocha Shake: ");
int mochaShake = scnr.nextInt();
        
System.out.print("Raspberry Green Tea: ");
int greenTea = scnr.nextInt();

Instead of putting an if-statement under each option, is there any other way I can output "invalid amount" under each option?

Methods, of course. You have a task:

Ask the user for a non-negative number.

So, write a method that encapsulates the job:

public int getAmount(Scanner scanner, String prompt) {
    while (true) {
        System.out.println(prompt);
        int v = scanner.nextInt();
        if (v >= 0) return v;
        System.out.println("Please enter positive numbers only.");
    }
}

note how you can now write 'if they mess up, ask again instead of outright quitting' exactly once, and reuse this as many times as you like.

@rzwitserloot's suggestion of writing a method to encapsulate the task of input, is the most straightforward, and probably most 'correct' method of doing this.

However, if you really don't want to write another function for whatever reason, you can make your variable names dynamic! Write them as a list of strings, iterate through those strings, and store them in a data structure (Map is probably the most straightforward).

Map<String, Integer> variables = new HashMap<>();
String[] variableNames = {
    "Small Coffee",
    "Medium Coffee",
    "Large Coffee",
    "Banana Berry Smoothie",
    "Mocha Shake", 
    "Raspberry Green Tea"
};
System.out.println("Please enter the number of each drink that you like to purchase:");
for (String drinkName : variableNames) {
    // ask for the amount of drink
    System.out.print(drinkName + ": ");
    int amount = scnr.nextInt();
    // error check
    if (amount < 0) {
        System.out.println("Invalid amount");
        System.exit(1);
    }
    // add to map
    variables.put(drinkName, amount);
}
    


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