扫描器要求输入两次并且只将第二个输入存储到数组中

Question

我正在 java 中使用条件创建一个 switch case 语句。如果一个人在 2 到 12 个月之间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，我的系统提示他们输入两次数字，并且只将第二个条目存储到数组中：Image of terminal prompting twice & Image of second entry only being stored to the array.

我认为这是因为我已经 'myMonths[index] = sc.nextInt();' 声明了两次，但我不知道如何在它不存在两次的情况下绕过它。谁能弄清楚为什么会这样，我该如何纠正？任何帮助将不胜感激。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

你可以在你的代码中尝试这样的事情

    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
}

关于如何使用 while 循环提示 ip 直到它有效的示例

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
}

扫描器要求输入两次并且只将第二个输入存储到数组中

Scanner asking for input twice and only storing second input to an array

java

arrays

loops

switch-statement

java.util.scanner