我剛剛遇到了哨兵控制迭代，并且遇到了一些困難。我必須編寫一個程序來獲取用戶使用的里程和加侖數，計算總英里數。我試圖使用 -1 作為哨兵值來在用戶完成時退出循環，但是當我輸入該值時，Java 不會終止程序。相反，它要求加侖的另一個值。如何讓它接受第一個輸入的哨兵值？例子：輸入英里或 -1 退出-1輸入加侖-1終止import java.util.Scanner;public class Activity3_17 { public static void main(String[] args) { Scanner input = new Scanner(System.in); // processing phase int miles = 1; int gallons = 1; int totalMiles = 0; int totalGallons = 0; float mpg = 0; System.out.println("Enter miles or -1 to exit"); miles = input.nextInt(); System.out.println("Enter gallons"); gallons = input.nextInt(); while (miles != -1) { System.out.println("Enter miles or -1 to exit"); miles = input.nextInt(); System.out.println("Enter gallons or -1 to exit"); gallons = input.nextInt(); totalMiles = totalMiles + miles; totalGallons = totalGallons + gallons; } if (miles == -1) { System.out.print("Terminate"); } else{ mpg = (float) totalMiles / totalGallons; System.out.println(mpg); } }}
4 回答
九州編程
TA貢獻1785條經驗 獲得超4個贊
您需要檢查用戶是否在while循環內輸入了-1。如果這樣做，請使用 退出循環break，然后終止程序。
mpg仍在循環內打印，但僅在進行檢查后打印。這確保用戶給出了有效的輸入。
我決定設置循環條件，因為如果ortrue為 -1 ，則循環應該中斷。miles gallons
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
int miles = 1;
int gallons = 1;
int totalMiles = 0;
int totalGallons = 0;
float mpg = 0;
while (true) {
System.out.println("Enter miles or -1 to exit");
miles = input.nextInt();
if (miles == -1) break;
System.out.println("Enter gallons or -1 to exit");
gallons = input.nextInt();
if (gallons == -1) break;
totalMiles = totalMiles + miles;
totalGallons = totalGallons + gallons;
mpg = (float) totalMiles / totalGallons;
System.out.println(mpg);
}
input.close();
System.out.print("Terminate");
}
大話西游666
TA貢獻1817條經驗 獲得超14個贊
只需在 while 循環中添加 2 個附加條件（如果帶有中斷）即可立即退出 while
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
// processing phase
int miles = 1;
int gallons = 1;
int totalMiles = 0;
int totalGallons = 0;
float mpg = 0;
System.out.println("Enter miles or -1 to exit");
miles = input.nextInt();
System.out.println("Enter gallons");
gallons = input.nextInt();
while (miles != -1) {
System.out.println("Enter miles or -1 to exit");
miles = input.nextInt();
if(miles == -1) break;
System.out.println("Enter gallons or -1 to exit");
gallons = input.nextInt();
if(gallons == -1) break;
totalMiles = totalMiles + miles;
totalGallons = totalGallons + gallons;
}
if (miles == -1) {
System.out.print("Terminate");
}
else{
mpg = (float) totalMiles / totalGallons;
System.out.println(mpg);
}
}
}
瀟瀟雨雨
TA貢獻1833條經驗 獲得超4個贊
這是完成的工作代碼：
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
int miles = 0;
int gallons = 0;
int totalMiles = 0;
int totalGallon = 0;
double mpg = 0;
double totalMpg = 0;
while(miles != -1){
System.out.println("Enter mileage or -1 to exit: ");
miles = input.nextInt();
if(miles == -1){
break;
}
System.out.println("Enter gallons or -1 to exit: ");
gallons = input.nextInt();
mpg = (double) miles / gallons;
System.out.printf("MPG: %.4f%n", mpg);
if(gallons == -1){
break;
}
totalMiles = totalMiles + miles;
totalGallon = totalGallon + gallons;
}
if (miles == -1){
totalMpg = (double) totalMiles / totalGallon;
System.out.printf("Total used is %.4f%n", totalMpg);
}
}
肥皂起泡泡
TA貢獻1829條經驗 獲得超6個贊
whileJava 僅在每次完成時評估循環。因此，您需要手動檢查是否為miles-1并打破循環。
while (miles != -1) {
System.out.println("Enter miles or -1 to exit");
miles = input.nextInt();
if (miles == -1) break;
System.out.println("Enter gallons or -1 to exit");
gallons = input.nextInt();
totalMiles = totalMiles + miles;
totalGallons = totalGallons + gallons;
}
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