Question

说我在某处有以下代码块：

while(condition){
    try {
        String twoStr= JOptionPane.showInputDialog("Enter two words sep by a space.");
        \\do stuff like splitting and taking an index which may cause out of bound exception
    catch (IOException e) {
        System.out.println("Sorry your words are terrible.");
     }

\\do stuff with twoStr

我无法访问try / catch语句之外的字符串，但我不想提示用户输入另外两个单词，以防他搞砸并输入单个单词。如何访问在try块中初始化的值？

Answer 1

字符串应该在try / catch语句之外定义：

while(condition){
    String twoStr = null;

    try {
        twoStr= JOptionPane.showInputDialog("Enter two words sep by a space.");
     } catch (IOException e) {
        System.out.println("Sorry your words are terrible.");
     }

     //do stuff with twoStr

通过这种方式，try / catch语句及其外部的代码都将看到变量。您应该阅读scopes以更好地了解这一点。

Answer 2

当您在string块中定义try catch时，它只对该块是本地的，并且无法在外部访问。在try catch块之外定义String变量，如下所示 -

while(condition){
String twoStr;
try {
    twoStr= JOptionPane.showInputDialog("Enter two words sep by a space.");
    //do stuff 
 }catch (IOException e) {
    System.out.println("Sorry your name is bad.");
 }
.....

Answer 3

更改twoStr

的范围

while(condition){
String twoStr= null;
    try {
         twoStr= JOptionPane.showInputDialog("Enter two words sep by a space.");
        \\do stuff like splitting and taking an index which may cause out of bound exception
    catch (IOException e) {
        System.out.println("Sorry your name is bad.");
     }

\\do stuff with twoStr

Answer 4

在try catch之外声明String。如果在try catch中声明一个变量，那么变量的范围仅适用于try catch内部。所以你不能在外面使用它。

 while(condition){
     String twoStr =null;
    try {
        twoStr= JOptionPane.showInputDialog("Enter two words sep by a space.");
       //do stuff like splitting and taking an index which may cause out of bound exception
       }
    catch (IOException e) {
        System.out.println("Sorry your words are terrible.");
     }

Answer 5

String twoStr = null;
while(condition){
     try {
        twoStr = JOptionPane.showInputDialog("Enter two words sep by a space.");
        \\do stuff like splitting and taking an index which may cause out of bound exception
    catch (IOException e) {
        System.out.println("Sorry your name is bad.");
     }

\\do stuff with twoStr

Answer 6

twoString是在try-catch块的上下文中定义的，因此无法访问它，而是需要在try-catch块之前定义变量...

while(condition){
    String twoStr = null;
    try {
        twoStr = JOptionPane.showInputDialog("Enter two words sep by a space.");
        //do stuff like splitting and taking an index which may cause out of bound exception
    } catch (IOException e) {
        System.out.println("Sorry your name is bad.");
    }

    // You now have access to twoStr

Answer 7

只需在try-block之外声明：

String twoStr = null;
while(condition){
    try {
        twoStr= JOptionPane.showInputDialog("Enter two words sep by a space.");
        \\do stuff like splitting and taking an index which may cause out of bound exception
    catch (IOException e) {
        System.out.println("Sorry your words are terrible.");
     }

\\do stuff with twoStr

Answer 8

您无法访问try catch块之外的字符串变量String twoStr，因为在try / catch块中声明的变量范围不在包含块的范围内，原因与所有其他变量声明的原因相同它们发生的范围是本地的。您需要从try catch块中声明该变量。

Java - Try / Catch - 如果成功，则访问try块中的变量

8 个答案: