程序从java开关中断
由于某种原因，当我在switch（切换）菜单上输入'1'时，不会发生任何事情，但程序不会终止。选项2-5也一样。默认选项工作正常。有人能帮我吗？谢谢 代码：程序从java开关中断,java,Java,由于某种原因，当我在switch（切换）菜单上输入'1'时，不会发生任何事情，但程序不会终止。选项2-5也一样。默认选项工作正常。有人能帮我吗？谢谢 代码： import java.util.Scanner; public class ConversionTrial { public static void main(String[] args) { double pound; double euro; double dollars; double yen;
import java.util.Scanner;
public class ConversionTrial {
public static void main(String[] args) {
double pound;
double euro;
double dollars;
double yen;
double rupees;
double poundEuro;
double poundDollars;
double poundYen;
double poundRupees;
int choice;
Scanner input = new Scanner(System.in);
Scanner exchange = new Scanner(System.in);
menu: while(true) {
System.out.println("Please choose an option:");
System.out.println("1. Enter values");
System.out.println("2. Euros (1GBP = 1.28EUR)");
System.out.println("3. Dollars (1GBP = 1.51USD)");
System.out.println("4. Yen (1GBP = 179.80JPY)");
System.out.println("5. Rupees (1GBP = 95.60INR)");
System.out.println("6. Exit");
choice = input.nextInt();
switch(choice){
case -1:
case 6:
break menu;
case 1:
pound = exchange.nextDouble();
System.out.print("Please enter your values you would like to exchange:");
break;
case 2:
pound = exchange.nextDouble();
euro = 1.28;
poundEuro = pound * euro;
System.out.println("Your amounts in Euros are" + poundEuro);
case 3:
pound = exchange.nextDouble();
dollars = 1.51;
poundDollars = pound * dollars;
System.out.println("Your amounts in Dollars are" + poundDollars);
case 4:
pound = exchange.nextDouble();
yen = 1.28;
poundYen = pound * yen;
System.out.println("Your amounts in Yen are" + poundYen);
case 5:
pound = exchange.nextDouble();
rupees = 1.28;
poundRupees = pound * rupees;
System.out.println("Your amounts in Rupees are" + poundRupees);
default:
System.out.println("You must enter an option between 1 and 6!");
}
}
input.close();
exchange.close();
}
}
菜单此外，您还错过了
中断在所有其他情况下。实际上不需要菜单标签。摆脱它，这是糟糕的代码气味
此外，您还错过了中断在所有其他情况下。为每种情况添加中断以退出switch语句。不确定这是否是您想要的答案，因此如果您正在寻找其他答案，请告诉我。为每个案例添加中断以退出switch语句。不确定这是否是您想要的答案，因此如果您正在寻找其他内容，请告诉我。首先，不要创建两个扫描仪对象。只要创建一个，并使用它
其次，在选项1-5中，在向用户输出任何内容之前，您正在等待输入，因此这可能就是它似乎不起作用的原因。您应该为预期值添加提示
第三，您缺少break在案例2-5的末尾
第四，使用标签通常不是做事情的最佳方式。最终可能会产生一些难以阅读的代码。更好的方法是使用标志变量，boolean exit=false。然后，while循环将基于它不为true而循环，while（！exit）
。在您的案例6:
，exit=true
第五，当用户不能选择-1退出时，为什么要选择-1退出？我会删除它
import java.util.Scanner;
public class ConversionTrial{
public static void main(String[] args) {
double pound;
double euro;
double dollars;
double yen;
double rupees;
double poundEuro;
double poundDollars;
double poundYen;
double poundRupees;
int choice;
Scanner input = new Scanner(System.in);
boolean exit = false;
while(!exit) {
System.out.println("Please choose an option:");
System.out.println("1. Enter values");
System.out.println("2. Euros (1GBP = 1.28EUR)");
System.out.println("3. Dollars (1GBP = 1.51USD)");
System.out.println("4. Yen (1GBP = 179.80JPY)");
System.out.println("5. Rupees (1GBP = 95.60INR)");
System.out.println("6. Exit");
choice = input.nextInt();
switch(choice){
case 6:
exit = true;
break;
case 1:
System.out.print("Please enter your values you would like to exchange: ");
pound = input.nextDouble();
break;
case 2:
System.out.print("Please enter your values you would like to exchange: ");
pound = input.nextDouble();
euro = 1.28;
poundEuro = pound * euro;
System.out.println("Your amounts in Euros are " + poundEuro);
break;
case 3:
System.out.print("Please enter your values you would like to exchange: ");
pound = input.nextDouble();
dollars = 1.51;
poundDollars = pound * dollars;
System.out.println("Your amounts in Dollars are " + poundDollars);
break;
case 4:
System.out.print("Please enter your values you would like to exchange: ");
pound = input.nextDouble();
yen = 1.28;
poundYen = pound * yen;
System.out.println("Your amounts in Yen are " + poundYen);
break;
case 5:
System.out.print("Please enter your values you would like to exchange: ");
pound = input.nextDouble();
rupees = 1.28;
poundRupees = pound * rupees;
System.out.println("Your amounts in Rupees are " + poundRupees);
break;
default:
System.out.println("You must enter an option between 1 and 6!");
break;
}
}
input.close();
}
}
编辑：作为奖励，我还注意到选项1实际上什么都不做。这是故意的吗？对于更干净的代码，我会在定义变量时初始化转换变量的值，而不是每次使用它们。您也可以在菜单中使用这些值，因此，如果值发生更改，只需更改一次即可。首先，不要创建两个扫描仪对象。只要创建一个，并使用它
其次，在选项1-5中，在向用户输出任何内容之前，您正在等待输入，因此这可能就是它似乎不起作用的原因。您应该为预期值添加提示
第三，您缺少break在案例2-5的末尾
第四，使用标签通常不是做事情的最佳方式。最终可能会产生一些难以阅读的代码。更好的方法是使用标志变量，boolean exit=false。然后，while循环将基于它不为true而循环，while（！exit）
。在您的案例6:
，exit=true
第五，当用户不能选择-1退出时，为什么要选择-1退出？我会删除它
import java.util.Scanner;
public class ConversionTrial{
public static void main(String[] args) {
double pound;
double euro;
double dollars;
double yen;
double rupees;
double poundEuro;
double poundDollars;
double poundYen;
double poundRupees;
int choice;
Scanner input = new Scanner(System.in);
boolean exit = false;
while(!exit) {
System.out.println("Please choose an option:");
System.out.println("1. Enter values");
System.out.println("2. Euros (1GBP = 1.28EUR)");
System.out.println("3. Dollars (1GBP = 1.51USD)");
System.out.println("4. Yen (1GBP = 179.80JPY)");
System.out.println("5. Rupees (1GBP = 95.60INR)");
System.out.println("6. Exit");
choice = input.nextInt();
switch(choice){
case 6:
exit = true;
break;
case 1:
System.out.print("Please enter your values you would like to exchange: ");
pound = input.nextDouble();
break;
case 2:
System.out.print("Please enter your values you would like to exchange: ");
pound = input.nextDouble();
euro = 1.28;
poundEuro = pound * euro;
System.out.println("Your amounts in Euros are " + poundEuro);
break;
case 3:
System.out.print("Please enter your values you would like to exchange: ");
pound = input.nextDouble();
dollars = 1.51;
poundDollars = pound * dollars;
System.out.println("Your amounts in Dollars are " + poundDollars);
break;
case 4:
System.out.print("Please enter your values you would like to exchange: ");
pound = input.nextDouble();
yen = 1.28;
poundYen = pound * yen;
System.out.println("Your amounts in Yen are " + poundYen);
break;
case 5:
System.out.print("Please enter your values you would like to exchange: ");
pound = input.nextDouble();
rupees = 1.28;
poundRupees = pound * rupees;
System.out.println("Your amounts in Rupees are " + poundRupees);
break;
default:
System.out.println("You must enter an option between 1 and 6!");
break;
}
}
input.close();
}
}
编辑：作为奖励，我还注意到选项1实际上什么都不做。这是故意的吗？对于更干净的代码，我会在定义变量时初始化转换变量的值，而不是每次使用它们。您也可以在菜单中使用这些值，因此，如果值发生变化，它们只需更改一次。就像Petermm所说的那样。你忘记了中断在您的案例中。
你的代码正在工作，但我认为它不是你想要它做的。
如果我按1，我可以输入一个double，然后它告诉我可以输入一个值。
但是开关1的这个值不会发生任何变化。
其他选项我可以输入一个double，然后用外币兑换
你打算做什么？就像彼得姆说的那样。你忘记了中断在您的案例中。
你的代码正在工作，但我认为它不是你想要它做的。
如果我按1，我可以输入一个double，然后它告诉我可以输入一个值。
但是开关1的这个值不会发生任何变化。
其他选项我可以输入一个double，然后用外币兑换
你打算做什么？刚刚运行了你的代码，我已经知道你想做什么了。我得到以下信息：
> Please enter your values you would like to exchange:Please choose an
> option:
> 1. Enter values
> 2. Euros (1GBP = 1.28EUR)
> 3. Dollars (1GBP = 1.51USD)
> 4. Yen (1GBP = 179.80JPY)
> 5. Rupees (1GBP = 95.60INR)
> 6. Exit 2
> 1.2 Your amounts in Euros are1.536
但请注意，必须输入双值。
此外，我坚持使用break退出交换机中存在的每种情况
“问候”刚刚运行了你的代码，我已经知道你想做什么了。我得到以下信息：
> Please enter your values you would like to exchange:Please choose an
> option:
> 1. Enter values
> 2. Euros (1GBP = 1.28EUR)
> 3. Dollars (1GBP = 1.51USD)
> 4. Yen (1GBP = 179.80JPY)
> 5. Rupees (1GBP = 95.60INR)
> 6. Exit 2
> 1.2 Your amounts in Euros are1.536
但请注意，必须输入双值。
此外，我坚持使用break退出交换机中存在的每种情况
关于当您选择选项1-5时，程序将等待另一个翻倍（您要转换的金额），然后才会响应。因此，选择一个选项，然后再给它一个双倍值，它会告诉你转换金额
import java.util.Scanner;
public class ConversionTrial {
public static void main(String[] args) {
double pound;
double euro;
double dollars;
double yen;
double rupees;
double poundEuro;
double poundDollars;
double poundYen;
double poundRupees;
int choice;
Scanner input = new Scanner(System.in);
Scanner exchange = new Scanner(System.in);
menu: while(true) {
System.out.println("Please choose an option:");
System.out.println("1. Enter values");
System.out.println("2. Euros (1GBP = 1.28EUR)");
System.out.println("3. Dollars (1GBP = 1.51USD)");
System.out.println("4. Yen (1GBP = 179.80JPY)");
System.out.println("5. Rupees (1GBP = 95.60INR)");
System.out.println("6. Exit");
choice = input.nextInt();
switch(choice){
case 1:
pound = exchange.nextDouble();
System.out.print("Please enter your values you would like to exchange:");
break;
case 2:
pound = exchange.nextDouble();
euro = 1.28;
poundEuro = pound * euro;
System.out.println("Your amounts in Euros are" + poundEuro);
break;
case 3:
pound = exchange.nextDouble();
dollars = 1.51;
poundDollars = pound * dollars;
System.out.println("Your amounts in Dollars are" + poundDollars);
break;
case 4:
pound = exchange.nextDouble();
yen = 1.28;
poundYen = pound * yen;
System.out.println("Your amounts in Yen are" + poundYen);
break;
case 5:
pound = exchange.nextDouble();
rupees = 1.28;
poundRupees = pound * rupees;
System.out.println("Your amounts in Rupees are" + poundRupees);
break;
case -1:
case 6:
break menu;
default:
System.out.println("You must enter an option between 1 and 6!");
}
}
input.close();
exchange.close();
}
}
当您选择选项1-5时，程序将等待另一个翻倍（您要转换的金额），然后才会响应。因此，选择一个选项，然后再给它一个双倍值，它会告诉你转换金额
import java.util.Scanner;
public class ConversionTrial {
public static void main(String[] args) {
double pound;
double euro;
double dollars;
double yen;
double rupees;
double poundEuro;
double poundDollars;
double poundYen;
double poundRupees;
int choice;
Scanner input = new Scanner(System.in);
Scanner exchange = new Scanner(System.in);
menu: while(true) {
System.out.println("Please choose an option:");
System.out.println("1. Enter values");
System.out.println("2. Euros (1GBP = 1.28EUR)");
System.out.println("3. Dollars (1GBP = 1.51USD)");
System.out.println("4. Yen (1GBP = 179.80JPY)");
System.out.println("5. Rupees (1GBP = 95.60INR)");
System.out.println("6. Exit");
choice = input.nextInt();
switch(choice){
case 1:
pound = exchange.nextDouble();
System.out.print("Please enter your values you would like to exchange:");
break;
case 2:
pound = exchange.nextDouble();
euro = 1.28;
poundEuro = pound * euro;
System.out.println("Your amounts in Euros are" + poundEuro);
break;
case 3:
pound = exchange.nextDouble();
dollars = 1.51;
poundDollars = pound * dollars;
System.out.println("Your amounts in Dollars are" + poundDollars);
break;
case 4:
pound = exchange.nextDouble();
yen = 1.28;
poundYen = pound * yen;
System.out.println("Your amounts in Yen are" + poundYen);
break;
case 5:
pound = exchange.nextDouble();
rupees = 1.28;
poundRupees = pound * rupees;
System.out.println("Your amounts in Rupees are" + poundRupees);
break;
case -1:
case 6:
break menu;
default:
System.out.println("You must enter an option between 1 and 6!");
}
}
input.close();
exchange.close();
}
}
可能是因为您调用了nextDouble
，所以它在等待一个双精度扫描仪？不要在System.in上创建两个扫描仪-只需创建一个并在任何地方使用它。可能是因为您调用了nextDouble
，所以它在等待一个双精度扫描仪？不要在System.in上创建两个扫描仪-只需创建一个并在任何地方使用它。