package mathloops3;
import java.util.*; import java.util.Random;
public class Program3 {
public static void main(String args[])
{
//======================================================================
//Input
//======================================================================
Scanner kb = new Scanner( System.in );
System.out.println("Please enter a non-negative integer: ");
int num1 = kb.nextInt();
while ( num1 == 0 || num1 <= 0 )
{
System.out.println("Please enter a non-negative integer: ");
num1 = kb.nextInt();
}
//======================================================================
//Menu
//======================================================================
System.out.println("Please make a choice");
System.out.println("0 Print the number");
System.out.println("1 Determine if the number is odd or even");
System.out.println("2 Find half of the number");
System.out.println("3 Find the reciprocal of the number");
System.out.println("4 Raise the number to the power of 5");
System.out.println("5 Raise the number to a power of 5");
System.out.println("6 Generate 20 random numbers between 0 and the number");
System.out.println("7 Find the sum of 0 up to your number");
System.out.println("8 Find the factorial of the number");
System.out.println("9 find the square root of the number");
System.out.println("10 Find the square root of the number");
System.out.println("11 Determine whether the number is prime");
System.out.println("12 Exit the Program");
//======================================================================
//Menu Choice Switch
//======================================================================
System.out.println("Please enter choice: ");
int menuChoice = kb.nextInt();
switch (menuChoice)
{
case 0: System.out.println("Yor number is " + num1 ); break;
case 1:
if ( num1 %2 == 0)
System.out.println( num1 + " is even!");
else
System.out.println( num1 + " is odd!");
break;
case 2: System.out.println("Half of " + num1 + " is " + num1 / 2); break;
case 3: System.out.println("The reciprocal of " + num1 + " is 1/" + num1 ); break;
case 4: System.out.println( num1 + " to the 5th power is "
+ (int)java.lang.Math.pow(num1,5)); break;
case 5:
double t = 1;
double b = num1;
double exponent = 5;
for ( int i = 1; i<=exponent; i++ )
t = t*b;
System.out.println(num1 + " to the 5th power is " + (int)t);
break;
case 6:
List<Integer> numbers = new ArrayList<Integer>();
int numberOfNumbersYouWant = 20; // This has to be less than 11
Random random = new Random();
do
{
int next = random.nextInt(20);
if (!numbers.contains(next))
{
numbers.add(next);
System.out.println(next);
}
} while (numbers.size() < numberOfNumbersYouWant);
break;
case 7:
for(int i = 1; i < num1; i++)
{
System.out.println(i);
}
break;
case 8:
int i,fact=1;
int number=num1;//It is the number to calculate factorial
for(i=1;i<=number;i++)
{
fact=fact*i;
}
System.out.println("Factorial of "+number+" is: "+fact);
break;
case 9:
int sqrt = num1;
System.out.println("The square root of " + num1 + " is " + (int)Math.sqrt(sqrt));
break;
case 10:
int sqrtloop=1;
int iterations=1;
int curSum = 0;
do
{
sqrtloop+=2; iterations++; curSum +=sqrtloop;
} while (curSum + sqrtloop < num1 );
System.out.println("The square root of " + num1 + " is " + iterations);
break;
case 11:
int num = num1;
boolean flag = false;
for(int prime = 2; prime <= num/2; ++prime)
{
// condition for nonprime number
if(num % prime == 0)
{
flag = true;
break;
}
}
if (!flag)
System.out.println(num + " is a prime number.");
else
System.out.println(num + " is not a prime number.");
break;
case 12:
System.out.println("Thank you, Bye-Bye!");
System.exit(0);
break;
}//end switch
do //details: this is where i am trying out different things with the do-while but i just cant seem to get it
right
{
if ( menuChoice != 12)
{
System.out.println("Please make a choice");
System.out.println("0 Print the number");
System.out.println("1 Determine if the number is odd or even");
System.out.println("2 Find half of the number");
System.out.println("3 Find the reciprocal of the number");
System.out.println("4 Raise the number to the power of 5");
System.out.println("5 Raise the number to a power of 5");
System.out.println("6 Generate 20 random numbers between 0 and the number");
System.out.println("7 Find the sum of 0 up to your number");
System.out.println("8 Find the factorial of the number");
System.out.println("9 find the square root of the number");
System.out.println("10 Find the square root of the number");
System.out.println("11 Determine whether the number is prime");
System.out.println("12 Exit the Program");
}
}while (menuChoice != menuChoice);
}//end main }//end class
我似乎无法重新打印菜单，我已经尝试了多种方法，但得出的结论是它必须是do-while循环，但是它将永久运行，或者将打印一次并然后终止程序。
答案 0 :(得分：0)
猜猜这会有所帮助：
do
{
//your switch case should be here
System.out.println("Please make a choice");
System.out.println("0 Print the number");
System.out.println("1 Determine if the number is odd or even");
System.out.println("2 Find half of the number");
System.out.println("3 Find the reciprocal of the number");
System.out.println("4 Raise the number to the power of 5");
System.out.println("5 Raise the number to a power of 5");
System.out.println("6 Generate 20 random numbers between 0 and the number");
System.out.println("7 Find the sum of 0 up to your number");
System.out.println("8 Find the factorial of the number");
System.out.println("9 find the square root of the number");
System.out.println("10 Find the square root of the number");
System.out.println("11 Determine whether the number is prime");
System.out.println("12 Exit the Program");
menuChoice =kb.nextInt();
}while (menuChoice >=0&&menuChoice<12);
答案 1 :(得分：0)
首先，您不能执行此操作（menuChoice！= menuChoice）;。这将永远是错误的。这就是它永远运行的原因。
因此请执行以下操作。
添加变量int，并像这样添加do
Scanner kb = new Scanner（System.in）;
int标志= 1;
做{
//在这里做你的事情
Sysout“输入2退出”；
标志= kb.nextInt（）;
} while（flag！= 2）`