在包含try-catch块的方法中返回一个对象（Java）

huangapple
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英文:

Returning an object within a method containing try-catch block (Java)

问题

  1. public static ReadCSVExample1 readBook(String filename, String serialNumber) {
  2.     try {
  3.         String line = "";
  4.         BufferedReader br = new BufferedReader(new FileReader(filename));
  5.         String foundName = "";
  6.         while ((line = br.readLine()) != null) {
  7.             String[] values = line.split(",");
  8.             for (int z = 0; z < values.length; z++) {
  9.                 if (values[z].equals(serialNumber)) {
  10.                     System.out.println(values[z] + " found!");
  11.                     foundName = values[z + 1];
  12.                     System.out.println(values[z + 2]);
  13.                     System.out.println(values[z + 3]);
  14.                 }
  15.             }
  16.         }
  17.         ReadCSVExample1 r = new ReadCSVExample1(foundName);
  18.         return r;
  19.     } catch (FileNotFoundException e) {
  20.         System.err.println(e);
  21.     } catch (IOException e) {
  22.         System.err.println(e);
  23.     }
  24.     ReadCSVExample1 r = new ReadCSVExample1(foundName);
  25.     return r;
  26. }
英文:

I wanted to return an object within a method that has a try-catch block. As shown below the method takes in a CSV file, reads the serialNumber and is supposed to return an object of the book with attributes such as name, year, etc., from the CSB file. I want to just return this object but I don't know where in the scope to return it given that foundName is local and thus I won't be able to return the new object r.

  1. public static ReadCSVExample1 readBook(String filename, String serialNumber){
  2.         try{
  3.             String line = &quot;&quot;;
  4.             BufferedReader br = new BufferedReader(new FileReader(filename));
  5.             String foundName = &quot;&quot;;
  6.             while ((line = br.readLine()) != null){
  7.                 String[] values = line.split(&quot;,&quot;);
  8.                 for (int z = 0; z&lt;values.length; z++){
  9.                     if (values[z].equals(serialNumber)){
  10.                         System.out.println(values[z]+ &quot; found!&quot;);
  11.                         foundName = values[z+1];
  12.                         System.out.println(values[z+2]);
  13.                         System.out.println(values[z+3]);
  14.                     }
  15.                 }
  16.             }
  17.         } catch (FileNotFoundException e){
  18.             System.err.println(e);
  19.         } catch (IOException e){
  20.             System.err.println(e);
  21.         }ReadCSVExample1 r = new ReadCSVExample1(foundName);
  22.         return r;
  23.     }

答案1

得分: 0

只需将foundName从try-catch块中移到外面，代码如下所示：

  1. public static ReadCSVExample1 readBook(String filename, String serialNumber){
  2.     String foundName = "";
  3.     try{
  4.         String line = "";
  5.         BufferedReader br = new BufferedReader(new FileReader(filename));
  6.         
  7.         while ((line = br.readLine()) != null){
  8.             String[] values = line.split(",");
  9.             for (int z = 0; z<values.length; z++){
  10.                 if (values[z].equals(serialNumber)){
  11.                     System.out.println(values[z]+ " found!");
  12.                     foundName = values[z+1];
  13.                     System.out.println(values[z+2]);
  14.                     System.out.println(values[z+3]);
  15.                 }
  16.             }
  17.         }
  18.     } catch (FileNotFoundException e){
  19.         System.err.println(e);
  20.         return null;
  21.     } catch (IOException e){
  22.         System.err.println(e);
  23.         return null;
  24.     }
  25.     ReadCSVExample1 r = new ReadCSVExample1(foundName);
  26.     return r;
  27. }
  29. 如果不将其放在try-catch块之外，`foundName`的作用域将限于try-catch块内部。如果将其移到外部，其作用域将是整个方法。
英文:

Just move the foundName outside the try-catch block like so:

  1. public static ReadCSVExample1 readBook(String filename, String serialNumber){
  2.        String foundName = &quot;&quot;;
  3.         try{
  4.             String line = &quot;&quot;;
  5.             BufferedReader br = new BufferedReader(new FileReader(filename));
  6.             
  7.             while ((line = br.readLine()) != null){
  8.                 String[] values = line.split(&quot;,&quot;);
  9.                 for (int z = 0; z&lt;values.length; z++){
  10.                     if (values[z].equals(serialNumber)){
  11.                         System.out.println(values[z]+ &quot; found!&quot;);
  12.                         foundName = values[z+1];
  13.                         System.out.println(values[z+2]);
  14.                         System.out.println(values[z+3]);
  15.                     }
  16.                 }
  17.             }
  18.         } catch (FileNotFoundException e){
  19.             System.err.println(e);
  20.             return null;
  21.         } catch (IOException e){
  22.             System.err.println(e);
  23.             return null;
  24.         }ReadCSVExample1 r = new ReadCSVExample1(foundName);
  25.         return r;
  26.     }

If it's not outside the try-catch block, the scope of foundName is within the try-catch block. If you move it outside, it's scope is the entire method.

huangapple
  • 本文由 发表于 2020年10月6日 05:51:37
  • 转载请务必保留本文链接：https://go.coder-hub.com/64216694.html
  • java
  • methods
  • object
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