java - 为什么我的代码会跳过 if 语句？

Question

我正在发布一段较大的代码块，但我遇到了问题。它应该自行运行。为了进行测试，只需在第一个提示时输入一个即可。一旦运行 print 语句，程序就会终止，而不是询问变量。我不明白为什么。有人可以帮助我吗？

import java.util.Scanner;

public class Physics {
  public static void main(String[] args) {
    Scanner input = new Scanner(System.in);

    int switchNumber;
    String variableCaseOne;
    double distance;
    double initialVelocity;
    double time;
    double gravity;

    System.out.println("This section is for projectile motion.");
    System.out.println("Which equation would you like to use?");
    System.out.println("1. Horizontal Equation: D = Vi * t");
    System.out.println("2. Vertical Equation: D = Vi * t - (1/2)g * (t^2)");
    switchNumber = input.nextInt();
    if (switchNumber == 1) {
      System.out.println("Tell me which variable you'd like to solve for.");
      variableCaseOne = input.nextLine();
      if (variableCaseOne.equals("d")) {
        System.out.println("Enter the Initial velocity.");
        initialVelocity = input.nextDouble();
        System.out.println("Enter the time.");
        time = input.nextDouble();
        System.out.println("Distance equals: " + initialVelocity * time);
      }

    }
  }
}

谢谢大家的帮助!

Answer 1

如果我理解正确，请尝试改变

variableCaseOne = input.nextLine();

至

variableCaseOne = input.next();

这对我有用

snpt

public static void main(String[] args)
{
    Scanner input = new Scanner(System.in);

    int switchNumber;
    String variableCaseOne;
    double initialVelocity;
    double time;

    System.out.println("This section is for projectile motion.");
    System.out.println("Which equation would you like to use?");
    System.out.println("1. Horizontal Equation: D = Vi * t");
    System.out.println("2. Vertical Equation: D = Vi * t - (1/2)g * (t^2)");
    switchNumber = input.nextInt();
    if (switchNumber == 1)
    {
        System.out.println("Tell me which variable you'd like to solve for.");
        variableCaseOne = input.next();
        if (variableCaseOne.equals("d"))
        {
            System.out.println("Enter the Initial velocity.");
            initialVelocity = input.nextDouble();
            System.out.println("Enter the time.");
            time = input.nextDouble();
            System.out.println("Distance equals: " + initialVelocity * time);
        }
    }
    input.close();
}