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Index › Programming Questions & Help › Syntax Questions › Change one letter in a string
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Change one letter in a string (Read 1134 times)
Chrisir
Change one letter in a string
Mar 3rd, 2010, 1:26pm  


I try something like:
buffer[bufferWritePosition][depth].setCharAt(i, "*");

or

buffer[bufferWritePosition][depth][i] =  "*";

but I don't have a clou...

How can I change one letter in an existing string?

The string is an 2D-Array, buffer[bufferWritePosition][depth], and I want to put the Position i to '*'.

Greetings, Chrisir
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TfGuy44
Re: Change one letter in a string
Reply #1 - Mar 3rd, 2010, 1:46pm  
String petName = "BULJDOG"; // Whoops. BULLDOG will not be happy!
int i = 3;
char a = 'L';
petName = petName.substring(0,i) + a + petName.substring(i+1);
// That's better.
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« Last Edit: Mar 3rd, 2010, 11:04pm by TfGuy44 »  
 
koogy
Re: Change one letter in a string
Reply #2 - Mar 3rd, 2010, 2:08pm  
StringBuffer might be a better bet as it's designed to be modifiable (that String code is creating copies all over the place. actually, it's probably using StringBuffer under the covers anyway)

StringBuffer has a method:
setCharAt(int index, char ch);
which sounds ideal

have been playing with javap -c and the following is TfGuy's code

Code:

    static void BullDog1() {
        String petName = "BULJDOG"; // Whoops. BULLDOG will not be happy!
        int i = 3;
        char a = 'L';
        petName = petName.substring(0,i) + a + petName.substring(i + 1);
    }


which generates:

Code:

static void BullDog1();
  Code:
   0:	ldc	#25; //String BULJDOG
   2:	astore_0
   3:	iconst_3
   4:	istore_1
   5:	bipush	76
   7:	istore_2
   8:	new	#4; //class java/lang/StringBuilder
   11:	dup
   12:	invokespecial	#5; //Method java/lang/StringBuilder."<init>":()V
   15:	aload_0
   16:	iconst_0
   17:	iload_1
   18:	invokevirtual	#26; //Method java/lang/String.substring:(II)Ljava/lang/String;
   21:	invokevirtual	#7; //Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
   24:	iload_2
   25:	invokevirtual	#27; //Method java/lang/StringBuilder.append:(C)Ljava/lang/StringBuilder;
   28:	aload_0
   29:	iload_1
   30:	iconst_1
   31:	iadd
   32:	invokevirtual	#28; //Method java/lang/String.substring:(I)Ljava/lang/String;
   35:	invokevirtual	#7; //Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
   38:	invokevirtual	#9; //Method java/lang/StringBuilder.toString:()Ljava/lang/String;
   41:	astore_0
   42:	return


and the following uses StringBuffer and setCharAt

Code:

    static void BullDog2() {
        StringBuffer petName = new StringBuffer("BULJDOG"); // Whoops. BULLDOG will not be happy!
        int i = 3;
        char a = 'L';
        petName.setCharAt(i, a);
    }


which generates:

Code:

static void BullDog2();
  Code:
   0:	new	#29; //class java/lang/StringBuffer
   3:	dup
   4:	ldc	#25; //String BULJDOG
   6:	invokespecial	#30; //Method java/lang/StringBuffer."<init>":(Ljava/lang/String;)V
   9:	astore_0
   10:	iconst_3
   11:	istore_1
   12:	bipush	76
   14:	istore_2
   15:	aload_0
   16:	iload_1
   17:	iload_2
   18:	invokevirtual	#31; //Method java/lang/StringBuffer.setCharAt:(IC)V
   21:	return


half as long... 8)
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Chrisir
Re: Change one letter in a string
Reply #3 - Mar 4th, 2010, 10:26am  
Hello!

Wonderful! Thank you so much!   Smiley

A function would look like this:


void draw () {
 println(ReplaceCharAt("Buljdog",'l',3));
}

String ReplaceCharAt(String Word, char ReplacingLetter, int AtPos ) {        
 StringBuffer StringBufferName = new StringBuffer(Word); // Word in which we replace        
 StringBufferName.setCharAt( AtPos, ReplacingLetter );    
 return (StringBufferName.toString());
} // func


could also be called via:
     println("before " + buffer[bufferWritePosition][depth] ) ;
     buffer[bufferWritePosition][depth] = ReplaceCharAt ( buffer[bufferWritePosition][depth], '*', i );
     println("after " + buffer[bufferWritePosition][depth] ) ;      

Thanks!   Smiley

Greetings,

Chrisir
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