扫描器请求输入两次，只将第二次输入存储到阵列中

Question

我用java编写了一个带条件的switch case语句。如果一个人在2到12个月的时间内将一个项目添加到系统中，它将被添加到一个数组中。如果项目持续时间小于2或大于12，系统应要求他们重新输入有效数字。出于某种原因，我的系统会提示他们输入两次数字，并且只存储数组中的第二个条目：终端提示两次的图像

我在想这是因为我有“myMonths[index]=sc.nextInt（）；”声明了两次，但是我不知道如果它不在那里两次，我该如何绕过它。有人能弄清楚为什么会发生这种情况，我该如何纠正它吗？非常感谢任何帮助。这是我的代码：

           //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

您可以在代码中尝试类似的内容

    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
}

一个示例，说明如何使用while循环来提示ip直到它有效为止

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
}