try块中的代码被忽略，为什么？

我是编程的新手，并且一直在尝试通过编写一个简单的将Caesar转换应用于某些文本的程序来学习Java的基础知识。我已经能够做到这一点，到目前为止，我的代码所做的是：

1. 询问用户他们希望将文本移动多少个单位。
2. 提示用户输入一些文本。
3. 应用多个单位进行凯撒平移并打印结果。

这是工作代码：

import java.util.Scanner;
class Shift{

public static void main(String[] args){

    //This will scan for user input.
    Scanner sc = new Scanner(System.in);
    System.out.print("Shift by this many characters (0-25): ");
    int shift = sc.nextInt();
    sc.nextLine();//Skips over the whitespace after the integer
    System.out.print("Enter Text: ");
    String input = sc.nextLine();
    sc.close();

    //Initialise a character array containing every letter in the alphabet. 
    char[] alphabetArray = {'a','b','c','d','e','f','g','h','i','j','k','l','m',
                            'n','o','p','q','r','s','t','u','v','w','x','y','z'};
    char[] alphabetArrayCaps = {'A','B','C','D','E','F','G','H','I','J','K','L','M',
                                'N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};

    //Initialise the two variables that will be used in the next step.
    char[] constantArray = input.toCharArray();
    char[] output = input.toCharArray();

    //Implement a Caesar shift by the given number of units.
    for (int i=0; i < constantArray.length; i++){ //cycles through the user input character by character
        for (int j=0; j <= 25; j++){ //cycles through the alphabet
            if (constantArray[i] == alphabetArray[j]){
                    output[i] = alphabetArray[(j+shift)%26];
            }
            else if (constantArray[i] == alphabetArrayCaps[j]){
                        output[i] = alphabetArrayCaps[(j+shift)%26];
            }
        }
    }
    System.out.println(output);
    }
    }

此代码的问题在于，当要求用户输入整数时，如果输入了其他任何内容，则会出现异常。我认为这将是学习处理异常的好地方，并且一直在参考本指南中有关如何为此使用try-catch块的信息。

我遇到的问题是代码（如下）似乎完全忽略了我的try块。我认为这是因为我的try块包含声明整数“ shift”的行，并且当我向下滚动到我的代码中实际使用“ shift”的位置时，我得到一条警告，指出“ shift不能解析为变量”，则无法编译。

这是导致问题的代码，唯一的区别是我已经在try块中加上了一行，并在其后添加了catch块，该块应该显示一条错误消息（尽管我还没有得到编译的代码，所以还没有还没有机会玩这个游戏，看看它实际上是做什么的）。

import java.util.Scanner;
class Shift{

public static void main(String[] args){

    //This will scan for user input.
    Scanner sc = new Scanner(System.in);
    System.out.print("Shift by this many characters (0-25): ");

    try {
        int shift = sc.nextInt();
    }
    catch (java.util.InputMismatchException e){
        System.err.println("InputMismatchException: " + e.getMessage());                        
    }

    sc.nextLine();//Skips over the whitespace after the integer
    System.out.print("Enter Text: ");
    String input = sc.nextLine();
    sc.close();

    //Initialise a character array containing every letter in the alphabet. 
    char[] alphabetArray = {'a','b','c','d','e','f','g','h','i','j','k','l','m',
                            'n','o','p','q','r','s','t','u','v','w','x','y','z'};
    char[] alphabetArrayCaps = {'A','B','C','D','E','F','G','H','I','J','K','L','M',
                                'N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};

    //Initialise the two variables that will be used in the next step.
    char[] constantArray = input.toCharArray();
    char[] output = input.toCharArray();

    //Implement a Caesar shift by the given number of units.
    for (int i=0; i < constantArray.length; i++){ //cycles through the user input character by character
        for (int j=0; j <= 25; j++){ //cycles through the alphabet
            if (constantArray[i] == alphabetArray[j]){
                    output[i] = alphabetArray[(j+shift)%26];
            }
            else if (constantArray[i] == alphabetArrayCaps[j]){
                        output[i] = alphabetArrayCaps[(j+shift)%26];
            }
        }
    }
    System.out.println(output);
    }
    }

那么，为什么这一小小的变化突然阻止了“转变”的宣布呢？