嵌套开关语句打印错误答案

Question

import java.io.*;
import java.util.*;
public class Planets 
{
public static void main(String[] args) throws IOException
{
Scanner in;
in = new Scanner(System.in);
boolean runAgain = true;
System.out.println("Starting program...nn");

double weight = getWeight();

while(runAgain)
{
String planet = getPlanet();
calculateWeight(weight, planet);

System.out.println("nWould you like to see your weight on a different planet? (Yes or No)");
String input = in.nextLine();
if(input.charAt(0)=='N' || input.charAt(0)=='n')
{
runAgain = false;
}
}

} //end main

public static double getWeight() throws IOException
{ //Prompts user to enter their weight
Scanner in;
in = new Scanner(System.in);
System.out.println("Greetings! This program calculates how much you would weigh on other planets.nnPlease enter your weight (lbs.): ");
double weight = in.nextDouble();
return weight;
}

public static String getPlanet() throws IOException
{ //Prompts user to enter their planet
Scanner in;
in = new Scanner(System.in);
System.out.println("nChoose your planet:nSunnMoonnSaturnnMercurynMarsnUranusnVenusnJupiternNeptune");
String planet = in.nextLine();
return planet;
}

public static void calculateWeight(double weight, String planet) throws IOException
{ //Outputs the weight of the given planet ; takes two parameters weight and planet
switch(planet.charAt(0))
{
case 's':
case 'S':
switch(planet.charAt(1))
{
case 'u':
case 'U':
System.out.println("Your weight on the Earth is " + weight + " lbs.nYour weight on the Sun is " + 27.94*weight);
break;
case 'a':
case 'A':
System.out.println("Your weight on the Earth is " + weight + " lbs.nYour weight on Saturn is " + .91*weight);
break;
}
case 'm':
case 'M':
switch(planet.charAt(1))
{
case 'o':
case 'O':
System.out.println("Your weight on the Earth is " + weight + " lbs.nYour weight on the Moon is " + .17*weight);
break;
case 'e':
case 'E':
System.out.println("Your weight on the Earth is " + weight + " lbs.nYour weight on Mercury is " + .37*weight);
break;
case 'a':
case 'A':
System.out.println("Your weight on the Earth is " + weight + " lbs.nYour weight on Mars is " + .38*weight);
break;
} 
case 'u':
case 'U':
System.out.println("Your weight on Earth is " + weight + " lbs.nYour weight on Uranus is " + .88*weight);
break;
case 'v':
case 'V':
System.out.println("Your weight on Earth is " + weight + " lbs.nYour weight on Venus is " + .90*weight);
break;
case 'j':
case 'J':
System.out.println("Your weight on Earth is " + weight + " lbs.nYour weight on Jupiter is " + 2.64*weight);
break;
case 'n':
case 'N':
System.out.println("Your weight on Earth is " + weight + " lbs.nYour weight on Neptune is " + 1.12*weight);
break;
} 
} 

} //end class

正在做CS101课的作业。我们的教授希望我们使用嵌套的switch语句和charAt来打印我们在特定星球上的体重，以确定用户正在谈论的是哪个星球。嵌套的switch语句没有按预期执行。

错误:当我选择Sun时，它输出Sun和Uranus的结果

当我选择月亮时，它输出月亮和天王星的结果

当我选择土星时，它输出土星，火星和天王星的结果。

当我选择水星时，它输出水星和天王星的结果

当我选择Mars时，它输出Mars和Mercury的结果。

我不明白为什么要打印多个行星的结果，即使索引处的字母不匹配。天王星、金星、木星和海王星工作得很好，和预期的一样。

Answer 1

您需要在嵌套的switch之后添加break语句，以便您将break从外部的switch中取出:

switch(planet.charAt(0))
{
case 's':
case 'S':
switch(planet.charAt(1))
{
case 'u':
case 'U':
...
break;
}
break; // this one is needed.
case 'm':
...

或者你可以标记switch语句，然后标记break outer;。

Answer 2

在每个case块的内容之后，您要将break取出。你的内的switch的case块可以做到这一点，但你的外部没有。在内部的switch的右括号之后和下一个case之前添加一个break;。

由于缺少break;，您直接滚动到下一个case块。