我是编程新手。 我甚至使用帮助制作了这段代码。 我想知道它为什么没有成功执行.. 当我尝试执行它时，我必须输入两次数字才能使它运行。 是或否退出也不起作用！
import java.util.*;
public class Cal{
public static void main (String[] args)
{
String i;
char in;
int sol;
int x;
int y;
System.out.println("Hello! \nWelcome to The Calculator");
System.out.println("Use the following Commands to use The Calulator, \nType the following letters: \na for Addition \ns for Subtraction \nm for for Multipication \nd for Division" );
Scanner keyIn = new Scanner(System.in);
do
{
System.out.println("Now enter the letter for you operation: ");
keyIn.nextLine();
i = keyIn.nextLine();
in = i.charAt(0);
if (in == 'a')
{
System.out.println("Type in the first number ");
keyIn.nextInt();
x = keyIn.nextInt();
System.out.println("Type in the second number ");
keyIn.nextInt();
y = keyIn.nextInt();
sol = x + y;
System.out.println("You chose + operation. \nAnswer = " + sol);
}
if (in == 's')
{
System.out.println("Type in your first number");
keyIn.nextInt();
x = keyIn.nextInt();
System.out.println("Type in the second number");
keyIn.nextInt();
y = keyIn.nextInt();
sol = x - y;
System.out.println("You chose + operation. \nAnswer = " + sol);
}
if (in == 'm')
{
System.out.println("Type in your first number");
keyIn.nextInt();
x = keyIn.nextInt();
System.out.println("Type in the second number");
keyIn.nextInt();
y = keyIn.nextInt();
sol = x * y;
System.out.println("You chose + operation. \nAnswer = " + sol);
}
if (in == 's')
{
System.out.println("Type in your first number");
keyIn.nextInt();
x = keyIn.nextInt();
System.out.println("Type in the second number");
keyIn.nextInt();
y = keyIn.nextInt();
sol = x / y;
System.out.println("You chose + operation. \nAnswer = " + sol);
}
System.out.println("Do you want to do another calculation? No:n Yes:y");
keyIn.nextLine();
}
while(keyIn.equals("y"));
if (keyIn.equals("n"));
System.exit(0);
}
}
答案 0 :(得分：1)
你一直在做：
`keyIn.nextLine（）;
i = keyIn.nextLine（）;`
这就是你必须输入两个输入的原因。第一个输入被浪费，然后第二个输入存储输入。
删除第一个keyIn.nextLine（）;然后离开：
＆＃39; i = keyIn.nextLine（）;`
你在哪里使用它。
因为它存储了单位，让你的程序对它进行评估。
答案 1 :(得分：0)
在您的代码中
System.out.println("Type in your first number");
keyIn.nextInt();
x = keyIn.nextInt();
你两次调用keyIn.nextInt（）。由于您不会将第一个结果存储在变量中，因此它会丢失。
您可以使用调试器轻松找到它。
答案 2 :(得分：0)
使用此功能，并查看评论：
import java.util.*;
public class Cal
{
public static void main (String[] args)
{
String i;
char in;
int sol;
int x;
int y;
System.out.println("Hello! \nWelcome to The Calculator");
System.out.println("Use the following Commands to use The Calulator, \nType the following letters: \na for Addition \ns for Subtraction \nm for for Multipication \nd for Division" );
Scanner keyIn = new Scanner(System.in);
do
{
System.out.println("Now enter the letter for you operation: ");
//keyIn.nextLine();
i = keyIn.nextLine(); // key input saved in variable!
in = i.charAt(0);
if (in == 'a')
{
System.out.println("Type in the first number ");
//keyIn.nextInt(); // key input would be lost here..
x = keyIn.nextInt(); // key input saved in variable
System.out.println("Type in the second number ");
//keyIn.nextInt();
y = keyIn.nextInt();
sol = x + y;
System.out.println("You chose + operation. \nAnswer = " + sol);
}
if (in == 's')
{
System.out.println("Type in your first number");
//keyIn.nextInt();
x = keyIn.nextInt();
System.out.println("Type in the second number");
//keyIn.nextInt();
y = keyIn.nextInt();
sol = x - y;
System.out.println("You chose + operation. \nAnswer = " + sol);
}
if (in == 'm')
{
System.out.println("Type in your first number");
//keyIn.nextInt();
x = keyIn.nextInt();
System.out.println("Type in the second number");
//keyIn.nextInt();
y = keyIn.nextInt();
sol = x * y;
System.out.println("You chose + operation. \nAnswer = " + sol);
}
if (in == 's')
{
System.out.println("Type in your first number");
//keyIn.nextInt();
x = keyIn.nextInt();
System.out.println("Type in the second number");
//keyIn.nextInt();
y = keyIn.nextInt();
sol = x / y;
System.out.println("You chose + operation. \nAnswer = " + sol);
}
System.out.println("Do you want to do another calculation? No:n Yes:y");
keyIn.nextLine();
}
while(keyIn.equals("y"));
if (keyIn.equals("n"));
System.exit(0);
答案 3 :(得分：0)
我修改了你的代码。请尝试以下方法：
public static void main (String[] args)
{
String i;
char in;
int sol;
int x;
int y;
System.out.println("Hello! \nWelcome to The Calculator");
System.out.println("Use the following Commands to use The Calulator, \nType the following letters: \na for Addition \ns for Subtraction \nm for for Multipication \nd for Division" );
Scanner keyIn = new Scanner(System.in);
do
{
System.out.println("Now enter the letter for you operation: ");
keyIn.nextLine();
i = keyIn.nextLine();
in = i.charAt(0);
if (in == 'a')
{
System.out.println("Type in the first number ");
keyIn.nextInt();
x = keyIn.nextInt();
System.out.println("Type in the second number ");
keyIn.nextInt();
y = keyIn.nextInt();
sol = x + y;
System.out.println("You chose + operation. \nAnswer = " + sol);
}
if (in == 's')
{
System.out.println("Type in your first number");
keyIn.nextInt();
x = keyIn.nextInt();
System.out.println("Type in the second number");
keyIn.nextInt();
y = keyIn.nextInt();
sol = x - y;
System.out.println("You chose + operation. \nAnswer = " + sol);
}
if (in == 'm')
{
System.out.println("Type in your first number");
keyIn.nextInt();
x = keyIn.nextInt();
System.out.println("Type in the second number");
keyIn.nextInt();
y = keyIn.nextInt();
sol = x * y;
System.out.println("You chose + operation. \nAnswer = " + sol);
}
if (in == 's')
{
System.out.println("Type in your first number");
keyIn.nextInt();
x = keyIn.nextInt();
System.out.println("Type in the second number");
keyIn.nextInt();
y = keyIn.nextInt();
sol = x / y;
System.out.println("You chose + operation. \nAnswer = " + sol);
}
System.out.println("Do you want to do another calculation? No:n Yes:y");
keyIn.nextLine();
}while(keyIn.equals("y"));
}