String .contains()

[brendanmcdonagh]

Hi all,

I was rather suprised to find that the String java api doesn't contain String.contains(char aChar) method. It has a similar method for a charsequence but not one for what i need.

So unless someone tells me im wrong I ve come up with a another way.

If i have a char aChar = 'x'

then a String aString = "test"

if i do this aString.indexOf(aChar);

will I either get the index number of aChar or -1 if it isn't in there??

So then i can return false if -1 is returned???

Regards

Brendan

[JosAH]

Yep, you can also use a String as an argument for the indexOf() method, e.g.
"foobar".indexOf("oba") == 2

kind regards,

Jos

[brendanmcdonagh]

cheers Jos,

I'm starting to think for myself!!

[brendanmcdonagh]

I'm not so smart after all....

aString = "three"
aChar = 'e'

What would be the return of aString.indexOf(aChar) because of multiple occurences?

[brendanmcdonagh]

    private void setStringBuffer()
    {
        int test = aString.indexOf(aChar);
        while(test != -1)
        {
            aStringBuffer.setCharAt(test, aChar);
            test = aString.indexOf(test + 1, aChar);
        }
 
 
    }
 

I think this is the way to check for multiple occurences and them to a stringbuffer. If it is do i need the +1 after test to start looking for more??

[JosAH]

    private void setStringBuffer()
    {
        int test = aString.indexOf(aChar);
        while(test != -1)
        {
            aStringBuffer.setCharAt(test, aChar);
            test = aString.indexOf(test + 1, aChar);
        }
 
 
    }
 

I think this is the way to check for multiple occurences and them to a stringbuffer. If it is do i need the +1 after test to start looking for more??

Yep, otherwise the last found char is found again and again. A bit of for-loop
crafting helps you out:

int nofCharInString(char aChar, String aString) { // assume String non-null
   int count= 0;
   for (int i= -1; (i= aString.indexOf(aChar, i+1)) >= 0; count++);
   return count;
}
 

kind regards,

Jos

[r035198x]

    private void setStringBuffer()
    {
        int test = aString.indexOf(aChar);
        while(test != -1)
        {
            aStringBuffer.setCharAt(test, aChar);
            test = aString.indexOf(test + 1, aChar);
        }
 
 
    }
 

I think this is the way to check for multiple occurences and them to a stringbuffer. If it is do i need the +1 after test to start looking for more??

The API specs for the String class will tell you exactly what happens with that String.indexOf method.

P.S Also google StringBuilder vs StringBuffer.

[brendanmcdonagh]

Hi again,

I have to use StringBuffer on this course but also know about StringBuilder from last course.

Please do not think i am just wanting someone to do my work for me as I don't, I get a buzz out of writing methods that have not required me consulting api or this website, it's just sometimes i can look forever and get no where without someones input, which I learn massively from.

I have a error

Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 1
at java.lang.StringBuffer.setCharAt(StringBuffer.java :211)
at tma01q3.Coder.setFeedback(Coder.java:64)
at tma01q3.Coder.updateState(Coder.java:79)
at tma01q3.Coder.turn(Coder.java:104)
at tma01q3.TestGame.main(TestGame.java:38)

which i think has something to do with this method

 
    private void setFeedback()
    {
        int test = codeWord.indexOf(currentGuess);
        System.out.println(test);
        while(test != -1)
        {
            feedback.setCharAt(test, currentGuess);
            test = codeWord.indexOf(test + 1, currentGuess);
 
        }
 
 
    }
 
 

Anybody see whats wrong, I am inputting a letter which is assigned to currentGuess, then I have a look at codeWord to see if it contains the letter(currentGuess) and if so setChar() of StringBuffer(feedback)

[r035198x]

From the API specs, setCharAt

Throws:
IndexOutOfBoundsException - if index is negative or greater than or equal to length().

[JosAH]

Hi again,

I have to use StringBuffer on this course but also know about StringBuilder from last course.

Please do not think i am just wanting someone to do my work for me as I don't, I get a buzz out of writing methods that have not required me consulting api or this website, it's just sometimes i can look forever and get no where without someones input, which I learn massively from.

I have a error

Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 1
at java.lang.StringBuffer.setCharAt(StringBuffer.java :211)
at tma01q3.Coder.setFeedback(Coder.java:64)
at tma01q3.Coder.updateState(Coder.java:79)
at tma01q3.Coder.turn(Coder.java:104)
at tma01q3.TestGame.main(TestGame.java:38)

which i think has something to do with this method

 
    private void setFeedback()
    {
        int test = codeWord.indexOf(currentGuess);
        System.out.println(test);
        while(test != -1)
        {
            feedback.setCharAt(test, currentGuess);
            test = codeWord.indexOf(test + 1, currentGuess);
 
        }
 
 
    }
 
 

Anybody see whats wrong, I am inputting a letter which is assigned to currentGuess, then I have a look at codeWord to see if it contains the letter(currentGuess) and if so setChar() of StringBuffer(feedback)

Suppose you have an empty StringBuffer and you find a character at position three
(test == 3). You can't set a character at position three in an empty StringBuffer.

kind regards,

Jos

[brendanmcdonagh]

So are stringbuffer and string different in that first letter in one is index 0 and first letter in another is 1??

As I set the capacity of stringbuffer to same as String

feedback = new StringBuffer(code.length());

thanks for keeping paience

[r035198x]

So are stringbuffer and string different in that first letter in one is index 0 and first letter in another is 1??

As I set the capacity of stringbuffer to same as String

feedback = new StringBuffer(code.length());

thanks for keeping paience

The capacity is of no consequence. It's the length which matters. See quote from the specs that I posted above again.

[brendanmcdonagh]

Ok, checked it again and there is no setLength() for stringBuffer, so unless someone can show me different I need to instantinate the StringBuffer with _ (underscore) as many times as there are characters in the String?? so then when i come to setChar() there won't be any out of bounds because of lack of lentgh??

Any ideas how, please:(

[brendanmcdonagh]

There is a setLength() you guys are the best!

[r035198x]

Ok, checked it again and there is no setLength() for stringBuffer, so unless someone can show me different I need to instantinate the StringBuffer with _ (underscore) as many times as there are characters in the String?? so then when i come to setChar() there won't be any out of bounds because of lack of lentgh??

Any ideas how, please:(

You need to initialize it with the String value itself not with just the String's length.
Check the constructors for it in the .... API specs.

[r035198x]

After initializing with the String itself, you can then use replaceAll to change every character to underscore.

[brendanmcdonagh]

There isn't a replaceAll method for StringBuffer??

[JosAH]

... or use an ordinary regular expression for that purpose:

String replaceNonChar(String s, char aChar) {
   return s.replaceAll("[^"+aChar+"]", "_");
}
 

kind regards,

Jos

[brendanmcdonagh]

ok im back to the reason i started this thread as my method isn't doing the job,

private void setFeedback()
    {
 
        int test = codeWord.indexOf(currentGuess);
 
        while(test != -1)
        {
            feedback.setCharAt(test, currentGuess);
            test = codeWord.indexOf(test, currentGuess);
 
        }
 
 
    }
 

It is only entering into the stringbuffer the first occurence of currentGuess, so if three was codeword, stringbuffer is only having _ _ _ e _ added to it when e is current guess.

I have tried with test and test + 1 which api says is where to start check from.

I thought ii'd sorted this one!

[r035198x]

Why not just use the replaceAll method on the toString of that StringBuffer?

[JosAH]

Why not just use the replaceAll method on the toString of that StringBuffer?

Didn't come my reply #18 through? ;-)

kind regards,

Jos

[r035198x]

Didn't come my reply #18 through? ;-)

kind regards,

Jos

I can see it here fine. The thread is becoming one of those. All the required ingredients have been posted here (more than once) so I'm out now.

[brendanmcdonagh]

sorry jos i know you are trying to help and have lost patience but #18 refers to replacing all charaters in stringbuffer with _. which i ve put on backburner for now.
My last question was more or less the same as the first in thios thread.

I know how to indexOf() for one character but the method i ve just pasted was a while loop to continue checking for multiple occurences b ut it's not doing it's job which as far as the api goes, it should.

private void setFeedback()
    {
 
        int test = codeWord.indexOf(currentGuess);
 
        while(test != -1)
        {
            feedback.setCharAt(test, currentGuess);
            test = codeWord.indexOf(test, currentGuess);
 
        }
 
 
    }
 

[JosAH]

Did you also overlook my reply #6?

kind regards,

Jos

[brendanmcdonagh]

I'm sorry for trying your patience today jos!

I got to the bottom of it in the end, it was just a case of having test and aChar the wrong way around.

Thank you so much for sticking in there!!

Brendan