Exceptions

Exceptions are subject to the "Catch or Declare Rule". This means you must do one of the following:

Catch the exception in the method that would generate the exception.

public Item getItemFromList(int index){
   try{
      if(index >= array.length)
         throw new Exception("Out of Bounds" + index);
      else{
         return array[index];
      }
   }
   catch(Exception e){
      // handle the exception generated in the try block
   }
}

Declare the exceptions that could occur from within a method.
```
public Item getItemFromList(int index) throws Exception{
   if(index >= array.length){
      throw new Exception("Out of Bounds" + index);
   }
   return array[index];
}
```
When using the Declare method Java will enforce the user of the getItemFromList() method to catch the exceptions that could be generated by the function (i.e. Exception). When a user does not catch that exception, Java produce a syntax error until the user properly handles that exception.
```
public void main(String[] args){
   Item i = getItemFromList(5); // this violates the Catch or Declare Rule
                                // causing a syntax error
}
```
To fix the syntax error that is produced in the previous example, Java requires use to place any statements that throw exceptions in a try/catch block.
```
public void main(String[] args){
   try{
      Item i = getItemFromList(5);
   }
   catch(Exception e){
      // Do something with the exception
   }
}
```

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CMSC 202 — Spring 2011

Exceptions