循环处理异常答案

【问题标题】：Looping for the handling exception循环处理异常
【发布时间】：2015-10-28 09:23:44
【问题描述】：

我可以问一个关于我的标题的问题吗？由于我是 java 新手，我对程序中的异常处理有点困惑。我需要做的是，当用户输入错误的输入时，异常需要循环。对于下面的编码，它只执行 ArrayOutOfBounds 异常。为什么当我输入字符串/符号/十进制值时不执行 FormatNumberException。它仅显示在输出部分，但不在 showMessageDialog 输出中。我尝试使用多个异常处理Catch Multiple Java Exception 并且仍然相同。你能帮我解决这个问题吗？任何答案将不胜感激。对不起我的英语不好。

public class TestRandomArray {

    public static void main(String[] args) {
        Random ran = new Random(); // create instant object from class Random.
        int array[] =new int[100]; //set an array variable with array size of 100
        int maxNumber = 150; //set the limit of the random number to generate

        for (int i = 0; i < array.length; i++) { 
            array[i] = ran.nextInt(maxNumber) + 1; //+1 means that the array number should not contain with 0 value. 1-150.
            //System.out.println(array[i]);                
        }
        //for(int i : array){
            //System.out.println(i + ",");  //this for method is other technique to print the list of array.
        //}        
            do {   
                    String input = JOptionPane.showInputDialog(null, "Enter index"); //Get input from user
                    int choosenIndex = Integer.parseInt(input); //change the string to int type.
                try {  
                    if(choosenIndex >= 0 || choosenIndex <= array.length)  
                        JOptionPane.showMessageDialog(null, "The value of choosen index in the array is : "
                        + array[choosenIndex]); //display the choosen index value.
                        System.exit(0);
                }catch (ArrayIndexOutOfBoundsException e){
                    if (choosenIndex < 0 || choosenIndex > array.length) {
                        JOptionPane.showMessageDialog(null,
                        "Index is out of bound. Enter from 0-99"); //display error for indexoutbound.
                    }
                }catch(NumberFormatException e){
                        JOptionPane.showMessageDialog(null, "Only integer allowed.");//display other error occured.
                }
            } while (true);
    }
}

【问题讨论】：

标签： java loops exception-handling

【解决方案1】：

Integer.parseInt(input);

此语句在您的 try 块之外。它必须在里面才能让您的程序跳转到catch(NumberFormatException e) 块。

【讨论】：

如果变量 'choosenIndex' 包裹在 try 块中，那么它将引发编译时异常，因为变量也用于 catch 块。
@Mr.VishalJGajera 然后你应该在 try/catch 块之外声明它。

【解决方案2】：

公共类 TestRandomArray {

public static void main(String[] args) {
    Random ran = new Random(); // create instant object from class Random.
    int array[] =new int[100]; //set an array variable with array size of 100
    int maxNumber = 150; //set the limit of the random number to generate

    for (int i = 0; i < array.length; i++) { 
        array[i] = ran.nextInt(maxNumber) + 1; //+1 means that the array number should not contain with 0 value. 1-150.

    }

        do {   
             int choosenIndex = 0;
                String input = JOptionPane.showInputDialog(null, "Enter index"); //Get input from user

            try {  

                  Integer.parseInt(input); //change the string to int type.
                if(choosenIndex >= 0 || choosenIndex <= array.length)  
                    JOptionPane.showMessageDialog(null, "The value of choosen index in the array is : "
                    + array[choosenIndex]); //display the choosen index value.
                    System.exit(0);
            }catch (ArrayIndexOutOfBoundsException e){
                if (choosenIndex < 0 || choosenIndex > array.length) {
                    JOptionPane.showMessageDialog(null,
                    "Index is out of bound. Enter from 0-99"); //display error for indexoutbound.
                }
            }catch(NumberFormatException e){
                    JOptionPane.showMessageDialog(null, "Only integer allowed.");//display other error occured.
            }
        } while (true);
}

}

【讨论】：

【解决方案3】：

请仅进行以下更改，它可以工作，

  int choosenIndex = 0;
            do {   
                    String input = JOptionPane.showInputDialog(null, "Enter index"); //Get input from user
                try {  
                     choosenIndex = Integer.parseInt(input); //change the string to int type.
                    if(choosenIndex >= 0 || choosenIndex <= array.length)  
                        JOptionPane.showMessageDialog(null, "The value of choosen index in the array is : "
                        + array[choosenIndex]); //display the choosen index value.
                        System.exit(0);
                }catch(NumberFormatException e){
                    JOptionPane.showMessageDialog(null, "Only integer allowed.");//display other error occured.
                }catch (ArrayIndexOutOfBoundsException e){
                    if (choosenIndex < 0 || choosenIndex > array.length) {
                        JOptionPane.showMessageDialog(null,
                        "Index is out of bound. Enter from 0-99"); //display error for indexoutbound.
                    }
                }
            } while (true);

【讨论】：