IlllegalArgumentException

[suhaas.mohandos@gmail.com]

I thought I started a thread which talked about the IllegalArgumentException(other than NullPointerException thread) but I don't seem to find that thread now. So posting it again.

From the complete reference book:

An IllegalArgumentException is thrown if an invalid argument is used.

An invalid argument will not pass through the compiler itself then how will an IllegalArgumentException be thrown?

[superhaNds]

"Thrown to indicate that a method has been passed an illegal or inappropriate argument." From the java doc

For example you rank, let's say, the priority of a task from 1 to 5 and passing anything else is an illegal argument to the set method for example

[suhaas.mohandos@gmail.com]

Show me a program which throws this exception

[PhHein]

String in = "1234";
doIt(in);

// snip


public void doIt(String param) throws IllegalArgumentException{
    if(param.length() > 3){
         throw new IllegalArgumentException("Parameter must not be longer than three characters! - " + param);
    }
    // rest of method
}

[superhaNds]

You can use this to validate method arguments. It is one of the most common thrown.

[suhaas.mohandos@gmail.com]

User defined exception anyone can throw. Show me one program which throws IlllegalArgumentException on its own. An illegal argument will not pass through compiler itself then how will the exception be thrown?

[DarrylBurke]

User defined exception anyone can throw. Show me one program which throws IlllegalArgumentException on its own. An illegal argument will not pass through compiler itself then how will the exception be thrown?

Did you read #2?

db

[superhaNds]

User defined exception anyone can throw. Show me one program which throws IlllegalArgumentException on its own. An illegal argument will not pass through compiler itself then how will the exception be thrown?

What do you mean "on its own" ? It's not a user defined exception, it's a run time exception. Maybe you misunderstood the word illegal.

[gimbal2]

Did you read #2?

db

or better yet, #4. But what it boils down to is - read the other replies before adding your own.

[suhaas.mohandos@gmail.com]

I read all the replies. #2 does not have a program example. #4 gives a program in which the IllegalArgumentException is thrown by the user(developer). I want to see a program in which IllegalArgumentException is generated by the system. Better still I want to see code in which the compiler allows the illlegal argument to be passed but at runtime the exception is thrown.

[gimbal2]

I want to see a program in which IllegalArgumentException is generated by the system.

That makes no sense at all. Of course it is triggered by the developer, 'the system' does not have a mind of its own, it does only what it is instructed to do.

[suhaas.mohandos@gmail.com]

Ok, lets take this example. Just run the below code and it throws a NoSuchElementException. Similary I want to see an IllegalArgumentException being thrown. Hope you will understand what I am looking for thru the example code pasted below.

import java.util.*;

public class QueueDemo
{
	public static void main(String arg[])
	{
		Queue q=new LinkedList();
		System.out.println(q.remove());
	}
}

Output:
Exception in thread "main" java.util.NoSuchElementException
at java.util.LinkedList.remove(Unknown Source)
at java.util.LinkedList.removeFirst(Unknown Source)
at java.util.LinkedList.remove(Unknown Source)
at QueueDemo.main(QueueDemo.java:8)

[gimbal2]

It is still a programmer 'doing it' - the programmer who wrote LinkedList.remove().

So what you are perhaps REALLY asking for is a standard JDK class that throws an IllegalArgumentException.

[suhaas.mohandos@gmail.com]

So what you are perhaps REALLY asking for is a standard JDK class that throws an IllegalArgumentException.
Ya, so you have an example?

[gimbal2]

Nope. But that doesn't mean there isn't a case. I suggest you yourself download the JDK source and do a code search if you really must know. I really don't care to know to be honest and it is not knowledge I ever needed in the ~10 years I have been professionally programming Java.

[DarrylBurke]

So what you are perhaps REALLY asking for is a standard JDK class that throws an IllegalArgumentException.
Ya, so you have an example?

Read the API for IllegalArgumentException
Click 'Use' at the top of the page
Read

db

[JosAH]

Better still I want to see code in which the compiler allows the illlegal argument to be passed but at runtime the exception is thrown.

Syntactically there's nothing wrong with the argument so the compiler would be happy; it's the semantics of the argument that don' make sense and an IAE will be thrown.

kind regards,

Jos

[jim829]

I am curious though. Why do you care if an example exists in the JDK? Throwing that exception from a method in the JDK is the same as using someone elses class whose method also throws the exception.

Regards,
Jim