掃描器要求輸入兩次並且只將第二個輸入存儲到數組中

Question

我正在使用條件在 java 中制作一個 switch case 語句。 如果一個人在 2 到 12 個月之間將一個項目添加到系統中，它將被添加到一個數組中。 如果項目持續時間小於 2 或大於 12，系統應要求他們重新輸入有效數字。 出於某種原因，我的系統提示他們輸入數字兩次，並且只將第二個條目存儲到數組中： Image of terminal prompting twice & Image of second entry only being stored to the array 。

我想這是因為我有 'myMonths[index] = sc.nextInt();' 聲明了兩次，但我不知道如何在不出現兩次的情況下繞過它。 誰能弄清楚為什么會這樣，我該如何糾正？ 任何幫助將不勝感激。 這是我的代碼：

           //Menu loop
            int myMonths[] = new int[5];
            int index = 0;
            while(choice !=6){


                switch (choice){
                case 1:
                //int n = number of projects
                int n = 1;
                Scanner sc = new Scanner(System.in);
                System.out.println("How many months was your project?");

                for(int i=0; i<1; i++){
                    myMonths[index] = sc.nextInt();
                    //if months is lesser than 2/greater than 12
                    if((myMonths[index] < 2) || (myMonths[index] > 12)){
                        System.out.println("Enter a number between 2 and 12 months");}

                   //if months is between 2 and 12 add it to the array
                    for(int x=0; x<1; x++){
                    //read the elements of the array
                    myMonths[index++]=sc.nextInt();}

Answer 1

    for(int i=0; i<1; i++){
                myMonths[index] = sc.nextInt();// put this in a variable int a = sc.nextInt();
                //if months is lesser than 2/greater than 12
                if((myMonths[index] < 2) || (myMonths[index] > 12)){
                    System.out.println("Enter a number between 2 and 12 months");}//here your are just checking if provided value is between 2 or 12 but there is no logical branching i.e. an else

               //if months is between 2 and 12 add it to the array
                for(int x=0; x<1; x++){
                //read the elements of the array
                myMonths[index++]=sc.nextInt();}//since there is no else this block will always execute

你可以在你的代碼中嘗試這樣的事情

    for(int i=0; i<1; i++){
                int ip = sc.nextInt();
                //if months is lesser than 2/greater than 12
                if((ip < 2) || ip > 12){
                    System.out.println("Enter a number between 2 and 12 months");
    //here ask for ip again
ip = sc.nextInt();//if you wanna continue doing this until you get a valid ip use an infinite while loop with a flag for break --- see below
}else{
//code for saving ip to array whatever logic you might need
}

一個關於如何使用 while 循環提示 ip 直到它有效的例子

int ip;
boolean valid = false;

while(!valid){
 ip = sc.nextInt();
if(condition){
//if codition is satisfied 
valid = true;
}

//else sysout("invalid ip"); loop will continue  until you get a valid ip
}