need to create loop to force user to input integer

How do i create a loop to force user to input an integer value?
I'm trying to use a while loop and store via keyboard.nextInt(), however as soon as a non integer is entered the program quits with an error.

Let's see that while loop, in the form of an SSCCE.

db

Code:

---

Scanner s = new Scanner(System.in);
int number = 0;
while(true) {
try {
System.out.println("please enter a valid number");
number=Integer.parseInt(s.next());
} catch(NumberFormatException nfe) {
continue;
}
System.out.println("Valid number entered!");
break;
}

---

Nice spoonfeed.

Quote:

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Originally Posted by Tolls

Nice spoonfeed.

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I don't agree. Smacks of GWBasic. I mean, both continue and break in the same loop where neither is really needed? pah!

db

So, not even an educational spoonfeed then?
I rarely bother reading the code on these things since they're often a bit scrappy...

Quote:

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Originally Posted by Tolls

So, not even an educational spoonfeed then?
I rarely bother reading the code on these things since they're often a bit scrappy...

---

I noticed that quite a lot of people, new themselves to Java or programming (I don't refer to their post count), try to post answers here; the advice is generally quite bad and those threads go berzerk where the OP leaves with some funny, crappy kind of advice.

kind regards,

Jos

I must admit, I've never used (nor seen) a continue-case. And after reading in my Java-bok, I'm still somewhat confused (the description there was extremely fuzzy)... Am I correct in assuming that with the code:

Code:

---

for (int i=0;i<10;i++)
{
  if (i%2==0)
    continue;
  System.out.println(i);
}

---

it would only print the odd numbers between 0 and 9?

Quote:

---

Originally Posted by Toll

I must admit, I've never used (nor seen) a continue-case. And after reading in my Java-bok, I'm still somewhat confused (the description there was extremely fuzzy)... Am I correct in assuming that with the code:

Code:

---

for (int i=0;i<10;i++)
{
  if (i%2==0)
    continue;
  System.out.println(i);
}

---

it would only print the odd numbers between 0 and 9?

---

Yep, the continue statement transfers the flow of control to the next loop iteration; it could've been written as follows:

Code:

---

for (int i= 0; i < 10; i++)
  if (i%2 != 0)
      System.out.println(i);

---

See? No continue statement is necessary here.

kind regards,

Jos

Assuming I've read that code right, yes.

ETA: Damn, too slow.

Yeah; it's about as useless as I thought it was, heh. As I said, never used it, and probably never will.

I wouldn't say useless.

It's often used to avoid unecessarily deep nesting, but that is often in a situation where you are bug fixing, and refactoring a loop is more pain than gain. In other words, you've found a situation where you don't need to process item x so, rather than "if not whatever" and then indenting a score of lines of logic (and potentially cocking that up), you'd just stick "if whatever, continue". Lazy, I know, but sometimes you just need to get a fix in.

Quote:

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Originally Posted by Tolls

I wouldn't say useless.

It's often used to avoid unecessarily deep nesting, but that is often in a situation where you are bug fixing, and refactoring a loop is more pain than gain. In other words, you've found a situation where you don't need to process item x so, rather than "if not whatever" and then indenting a score of lines of logic (and potentially cocking that up), you'd just stick "if whatever, continue". Lazy, I know, but sometimes you just need to get a fix in.

---

Yep, a continue statement may reduce the indentation level; have a look; this:

Code:

---

for (<for-loop-header>)
  if (<condition1>)
      if (<condition2>)
        <large block of statments here>

---

... could've been written as:

Code:

---

for (<for-loop-header>) {
  if (!<condition1> || !<condition2>) continue;
  <large block of statments here>
}

---

... but then again those <conditions> may become to look 'unnatural' ;-)

kind regards,

Jos

My code is completely correct, I added the continue because it makes more sense that way. You guys haven't done shit so shut your negative mouths up.

Oh yes.
I only mention it in terms of bug fixing, largely because I would (when writing from scratch) tend to break the loop down into more method calls. Something I would do in bug fixing if (for whatever reason) I didn't invariably enter lazy-mode. That's usually down to working on someone elses byzantine code, though.

My stuff tends to look like:

Code:

---

for (MyData myData: lotsOfData) {
    if (dealWithThisOne(myData)) {
        processMyData(myData);
    }
}

---

Quote:

---

Originally Posted by Solarsonic

My code is completely correct, I added the continue because it makes more sense that way. You guys haven't done shit so shut your negative mouths up.

---

Crikey.

Still a spoonfeed, though...

Quote:

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Originally Posted by Solarsonic

My code is completely correct, I added the continue because it makes more sense that way. You guys haven't done shit so shut your negative mouths up.

---

Between legally (read: syntactically and semantically) correct code and elegant code lies a world of experience. But indeed I never did much with shit, is it a very smelly job?

kind regards,

Jos

Quote:

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Originally Posted by JosAH

Between legally (read: syntactically and semantically) correct code and elegant code lies a world of experience. But indeed I never did much with shit, is it a very smelly job?

kind regards,

Jos

---

I've got 5 kids...take it from me, it's a smelly job.

If I may rewrite the code to flow more naturally (at least to me):

Code:

---

Scanner s = new Scanner(System.in);
int number = 0;
boolean validNumber=false;
while(!validNumber)
{
  try
  {
    System.out.println("Please enter a valid number:");
    number=Integer.parseInt(s.next());
    validNumber=true;
    System.out.println("Valid number entered!");
  }
  catch(NumberFormatException nfe)
  {
    System.out.println("Not a valid number!");
  }
}

---

No more break, no more continue, and no while(true) loop (I've always despised those myself, even though they do have their place at times)

Quote:

---

Originally Posted by Tolls

I've got 5 kids...take it from me, it's a smelly job.

---

Five kids? Well, consider it your own fault then ;-)

kindest regards,

Jos