What's wrong with this For loop?

Question

I can't get this program to count the spaces, I have a feeling there is a logic error in the loop, but I am too inexperienced to figure it out myself. Any tips?

System.out.print("Enter a string: ");
String myString = keyboard.next();
int numBlanks = 0;

//find string length
int length = myString.length() - 1;
System.out.println("length " + length);

for(int sequence = 0; sequence >= length; ++sequence);
{

    if(myString.charAt(length)==' ')
    {
        numBlanks += 1;
        length -= length;
    }
    else 
        length -= length;

}

( With standard coding conventions, you wouldn't get the problem of the spurious semicolon on the for loop. ) — Tom Hawtin - tackline
– Tom Hawtin - tackline, Commented Sep 26, 2010 at 15:49

codaddict · Accepted Answer · 2010-09-26 15:11:09Z

9

There are few bugs I can see:

Semicolon at the end of for loop. Remove it.

sequence >= length

should be

sequence <= length

and

if(myString.charAt(length)==' ')

should be

if(myString.charAt(sequence)==' ')

and you need to change length at all as you are already changing sequence.

So we get:

for(int sequence = 0; sequence <= length; ++sequence) {

    if(myString.charAt(sequence)==' ') {
        numBlanks += 1;
    }
}

edited Sep 26, 2010 at 15:11

answered Sep 26, 2010 at 15:05

codaddict

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1 Comment

barrowc Over a year ago

+1 but think there should be a "don't" in: and you need to change length at all

Jonathan Grynspan · Accepted Answer · 2010-09-26 15:05:44Z

3

sequence >= length is spoken aloud as "sequence is greater than or equal to length." It is initialized to zero. When will it be greater than or equal to length?

answered Sep 26, 2010 at 15:05

Jonathan Grynspan

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Comments

Carl Manaster · Accepted Answer · 2010-09-26 15:12:59Z

1

In addition to the errors others have pointed out, there are violations of convention here; you're calculating the length as n - 1, and then comparing <= (well, >=, but should be <=). Typically, unless there is very good reason, our for loops look like this:

for (int i = 0; i < n; i++) {
    ...
}

In your case, this would be expressed as:

for (int i = 0; i < myString.length(); i++) {
    ...
}

It is also conventional to stick with "i" as the loop variable, unless there's good reason to use another; in your case, "sequence" is just confusing.

answered Sep 26, 2010 at 15:12

Carl Manaster

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Comments

Gordon Gustafson · Accepted Answer · 2010-09-26 15:06:35Z

0

First issue:

change

for(int sequence = 0; sequence >= length; ++sequence);

to

for(int sequence = 0; sequence <= length; ++sequence);  //flipped >= to <=

Second issue:

change

I am too inexperienced to figure it out myself.

to

This will be some good practice for debugging.  //int confidence should never be negative

:D

answered Sep 26, 2010 at 15:06

Gordon Gustafson

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1 Comment

Grodriguez Over a year ago

While you're fixing the 'first issue', remember to also remove the extra semicolon at the end of the for sentence :-)

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