Java 压缩 try/catch 代码异常

Question

Is there any way to compress the try/catch block codes? Right now, my code has a try/catch code inside a try/catch code.

if(petType.equals("DOG")) {

  try {
    String name = input.next();
    String owner = input.next();
    double weight = input.nextDouble();
    SimpleDateFormat stdDate = new SimpleDateFormat("MM/dd/yy");

    try {
      Date vaccineDate = stdDate.parse(input.next());
      boolean fixed = input.nextBoolean();
      Dog x = new Dog(name,owner,weight,vaccineDate,fixed);
      object.addPet(x);
    } 
    catch (ParseException ex) {
      System.out.println("ERROR - Vaccine date " + input.next() + " is not in mm/dd/yy format!");
      input.nextLine();
    }

  }
  catch(NoSuchElementException ex) {
    System.out.println("ERROR - Missing fields. Skipping line " + lineNumber + "...");
    input.nextLine();
  }

}

Answer 1

You could do this

if(petType.equals("DOG")) {

  try {
    String name = input.next();
    String owner = input.next();
    double weight = input.nextDouble();
    SimpleDateFormat stdDate = new SimpleDateFormat("MM/dd/yy");
    Date vaccineDate = stdDate.parse(input.next());
    boolean fixed = input.nextBoolean();
    Dog x = new Dog(name,owner,weight,vaccineDate,fixed);
    object.addPet(x);
  }
  catch(NoSuchElementException ex) {
    System.out.println("ERROR - Missing fields. Skipping line " + lineNumber + "...");
    input.nextLine();
  }
  catch (ParseException ex) {
    System.out.println("ERROR - Vaccine date " + input.next() + " is not in mm/dd/yy format!");
    input.nextLine();
  }
}

Or with Java 7

try {
...
} catch(ParseException | NoSuchElementException ex) {
...
}   

If that's what you meant by compression.

Answer 2

1st of all, a single try block can be followed by a series of catch blocks:

try {
    throw IOException("msg");
    ...
    throw InterruptedException("msg");
}
catch (IOException ioe){
    ...
 } catch (InterruptedException ie) {
    ...
 }

This is not the best practice, because you might want to narrow your try/catch blocks to handle smaller content of code regarding the Exceptions

Answer 3

You can only use one try block, and then use catch(Exception ex) to catch all those exceptions. If you want to react to the specific kind of exception, you have to test for it.

Answer 4

You can do it (see below). But you might want to think about the structure of your code, for example, maybe you can restructure so that you don't have to call input.nextLine in each catch block.

if(petType.equals("DOG")) {

  try {
    String name = input.next();
    String owner = input.next();
    double weight = input.nextDouble();
    SimpleDateFormat stdDate = new SimpleDateFormat("MM/dd/yy");

    Date vaccineDate = stdDate.parse(input.next());
    boolean fixed = input.nextBoolean();
    Dog x = new Dog(name,owner,weight,vaccineDate,fixed);
    object.addPet(x);    
  }
  catch (ParseException ex) {
    System.out.println("ERROR - Vaccine date " + input.next() + " is not in mm/dd/yy format!");
    input.nextLine();
  }
  catch(NoSuchElementException ex) {
    System.out.println("ERROR - Missing fields. Skipping line " + lineNumber + "...");
    input.nextLine();
  }    
}

Answer 5

Personally, I don't like nesting try/catch blocks. I wouldn't write it this way; I'd prefer it more like this:

if(petType.equals("DOG")) {

  String vaccineDateString;
  try {
      String name = input.next();
      String owner = input.next();
      double weight = input.nextDouble();
      DateFormat stdDate = new SimpleDateFormat("MM/dd/yy");
      stdDate.setLenient(false);
      vaccineDateString = input.next();
      Date vaccineDate = stdDate.parse(vaccineDateString);
      boolean fixed = input.nextBoolean();
      Dog x = new Dog(name,owner,weight,vaccineDate,fixed);
      object.addPet(x);
    } catch (ParseException ex) {
        System.out.println("ERROR - Vaccine date " + vaccineDateString + " is not in MM/dd/yy format!");
        input.nextLine();
    } catch(NoSuchElementException ex) {
        System.out.println("ERROR - Missing fields. Skipping line " + lineNumber + "...");
        input.nextLine();
    }
}

I would also look askance at your mingling input with all this other stuff. I'd find another way.