Exception

[sujesh Katri]

some one please tell me

1	package com.result.exam.a;
2	
3	public abstract class Concept
4	{
5	  private String id;
6	
7	  protected Concept( String anId )
8	  {
9	    if ( anId == null ) 
10	    {
11	      throw new NullPointerException( "id must not be null" );
12	    }
13	
14	    id = anId;
15	  }

my brother wrote throw new NullPointerException("...");....is it correct or not....i think he must be write System.out.println("...")throws NullPointerException;thanks

[Ulf Dittmer]

"Correct" in what sense?

[sujesh Katri]

....
 if ( anId == null ) 
10	    {
11	      throw new NullPointerException( "id must not be null" );------->is it correct or not.
12	    }
13	
14	    id = anId;
15	  }

my lecturer said we always write throw inside the method only and when we write throw in the method body then we must be write throws in the context of method heading..please tell me.

[Paweł Baczyński]

sujesh Katri wrote:my brother wrote throw new NullPointerException("...");....is it correct or not....i think he must be write System.out.println("...")throws NullPointerException;thanks

He can do this because NullPointerException is an unchecked exception.
The syntax you proposed is illegal. Keyword throws belongs to a signature of a method (a method definition), not the method call.

sujesh Katri wrote:my lecturer said we always write throw inside the method only and when we write throw in the method body then we must be write throws in the context of method heading..please tell me.

That is correct except for unchecked exceptions. See this.

[Ulf Dittmer]

That is not entirely correct. Unchecked exceptions do not need to be declared via "throws". Read http://docs.oracle.com/javase/tutorial/essential/exceptions/index.html to learn what the differences between checked and unchecked exceptions are.

Also, if a checked exception is thrown and subsequently caught in the same method body, it does not need to be declared either (because it does not leave the method).