Checking that all elements in collection meet a condition

[Ciwan]

Hello Java Friends.

I have an ArrayList of things (Nodes<Adjustment> to be precise). And I want to check that every single one of the elements in the ArrayList, meet a certain condition. If condition is met by all, then I want to return True and do something. If one or two don't meet the condition then I want to return a False and not do the thing.

I am not really sure whether there is a technical name for what I'm trying to achieve. But here's some pseudo-code for what I'm trying to do:

if(nodesUsed.contains(each of the nodes in the ArrayList<Node<Adjustment>>))
{
     //then we do this
} else {
     //we do something else
}

As always, any help would be greatly appreciated.

Thank You.

[KevinWorkman]

You're going to have to loop through the ArrayList (or use an Iterator) and check each element against whatever condition you want.

[Ciwan]

Hello KevinWorkman

You mean like this:

for(Node<Adjustment> n : g.get(x)) // for each neighbours of [x]
{
     if(nodesUsed.contains(n.getName())
     {
          // Do Code00
     }
}

Cause that is what I thought initially, but then I realised that { Code00 } will run even if only one of the elements in the Array met the condition

I only want Code00 to run if ALL the Elements in the Array meet the condition.

Thanks

[Dark]

What about a while loop? While its true it will continue going through your code, if the boolean ever becomes false or if you reach the end of your array list using an iterator you can insert a break statement. Then check outside of the loop if your boolean is true, and if it is then run code00.

I'm a bit tired, and this has a chance of being completely retarded, so I would verify with someone else that this is a good idea. It makes sense in my head, but I have no idea if it is displayed properly. Anyways I'm off, I need sleep. I hope this helped.

[Ciwan]

Hi Dark

I hadn't thought of a while loop to be honest. Do mean like so:

for(Node<Adjustment> n : g.get(x)) // for each neighbours of [x]
{
	while(nodesUsed.contains(n))
	{
		// Do Code00
	}
}

In the above, wouldn't Code00 run even if only one of the elements meets the condition ?

Thanks, Wish you a good night sleep

[KevinWorkman]

How would you do this by hand, or with a piece of paper and a pencil?

You'd look look through the list, and if you saw an element that did NOT meet the condition, you'd stop looking through the list and not do anything else. You'd know that all of the elements met the condition once you reached the end of the list.

[JosAH]

I hadn't thought of a while loop to be honest. Do mean like so:

No, not like so; more like so:

boolean allSatisfied= true;
for (T element : collection) 
   if (!condition(element)) {
      allSatisfied= false;
      break;
   }
if (allSatisfied)
   // Do Code00

kind regards,

Jos

[Ciwan]

Based on what Kevin and JosAH said, my code looks like this now:

for(Node<Adjustment> n : g.get(x)) // for each neighbours of [x]
{
	while(!nodesUsed.contains(n))
	{
		break;
	}

	// Do Code00
}

Have I messed up again ? or it correct this time ? It certainly seems OK when I run it through my head.

[JosAH]

Based on what Kevin and JosAH said, my code looks like this now:

for(Node<Adjustment> n : g.get(x)) // for each neighbours of [x]
{
	while(!nodesUsed.contains(n))
	{
		break;
	}

	// Do Code00
}

Have I messed up again ? or it correct this time ? It certainly seems OK when I run it through my head.

I never said anything like that and I'm sure Kevin did neither. Reread Kevin's and my reply again (carefully) and try again.

kind regards,

Jos

[Junky]

Use a method that returns a boolean. As soon as you find an element that does not meet the requirement return false. If you get to the end of the method all elements must meet the requirement so return true.

[Tolls]

Use a method that returns a boolean. As soon as you find an element that does not meet the requirement return false. If you get to the end of the method all elements must meet the requirement so return true.

This here.
You have a requirement that essentially says "if all elements in node pass this test then do this".
Your method would answer the "do all elements in node pass this test" part.

[Dark]

JosAH said to loop through your code, in the for loop he provided you would then check your conditions. If any condition that must be met was not met then you would set the boolean variable to false, break out of the loop and continue to the following if statement that would only run if your boolean was true. If the loop finished you would simply continue down to the if statement and do code00 would run.