java - 如何在 Java 中重复 if 条件？

Question

基本上，我希望能够输入一个不是选项的数字，然后再次提供选择的选项，并重复该语句。

Scanner keyboard = new Scanner(System.in);
    double weight;
    int Choice;

    System.out.println("What is your weight in pounds?");
    weight = keyboard.nextDouble();

    System.out.println("Which planet would you like to see your weight on?\n 1. Venus   2. Mars 3. Jupiter\n 4. Saturn  5. Uranus   6. Neptune");
    Choice =keyboard.nextInt();

    if (Choice == 1){
        System.out.println("Your weight on Venus would be " + (weight * 0.78));
    }
    else if (Choice == 2){
        System.out.println("Your weight on Mars would be " + (weight * .39));
    }
    else if (Choice == 3){
        System.out.println("Your weight on Jupiter would be " + (weight * 2.65));
    }
    else if (Choice == 4){
        System.out.println("Your weight on Saturn would be " + (weight * 1.17));
    }

    else if (Choice == 5){
        System.out.println("Your weight on Uranus would be" +(weight * 1.05));
    }
    else if (Choice == 6) {
        System.out.println("Your weight on Neptune would be " + (weight * 1.23));
    }
    else
        System.out.println("This was not a choice, try again!");
        Choice = keyboard.nextInt();
}

Answer 1

这是一种更简单的方法，使用 do-while 循环和 switch。

也固定选择

Scanner keyboard = new Scanner(System.in);
double weight;
int choice;

System.out.println("What is your weight in pounds?");
weight = keyboard.nextDouble();

do {
    System.out.println("Which planet would you like to see your weight on?\n 1. Venus   2. Mars 3. Jupiter\n 4. Saturn  5. Uranus   6. Neptune\n 7. Exit");
    choice = keyboard.nextInt();
    switch(choice) {
        case 1:
            System.out.println("Your weight on Venus would be " + (weight * 0.78));
            break;
        case 2:
            System.out.println("Your weight on Mars would be " + (weight * .39));
            break;
        case 3:
            System.out.println("Your weight on Jupiter would be " + (weight * 2.65));
            break;
        case 4:
            System.out.println("Your weight on Saturn would be " + (weight * 1.17));
            break;
        case 5:
            System.out.println("Your weight on Uranus would be" +(weight * 1.05));
            break;
        case 6:
            System.out.println("Your weight on Neptune would be " + (weight * 1.23));
            break;
        case 7:
            System.out.println("Bye");
            break;
        default:
            System.out.println("This was not a choice, try again!");
            break;
    }
} while (choice != 7);