Synchronizing Block code

[wong sheena]

  public class BufferThread extends Thread{
 
private StringBuffer buffer;
 
BufferThread(StringBuffer buffer){
 
this.buffer = buffer;
}
 
public void run(){
 
synchronized(buffer){

for(int counter = 1;counter<=10;counter++) 
{
System.out.println(buffer.toString());
}

if(buffer.toString().equals("A")) //line 1
{
buffer.setCharAt(0,'B');
}
else if(buffer.toString().equals("B"))
{
buffer.setCharAt(0,'C');

}

}
}

public static void main(String args[]){

StringBuffer myBuffer = new StringBuffer("A");
BufferThread one = new BufferThread(myBuffer);
BufferThread two = new BufferThread(myBuffer);
BufferThread three = new BufferThread(myBuffer);
 

one.start();
two.start();
three.start();


}
 
}
  

Hi guys, this is the exercise 9 -2 on pg 710 of k & b. I did a comparison at line 1 and change the StringBuffer object. Is there any other way to do the comparison and increment the letter?

[Giovanni Murguia]

Hello!

You could try something like:

  
char letter = buffer.charAt(0);
buffer.setCharAt(0, letter+1);

Giovanni

[Brad Clarke]

This particular exercise baffled me, but for a different reason this time

The verbiage of the question states "You can check Chapter 6 for StringBuffer methods that will help with this." so I took it literally to mean that the only methods that applied to the exercise were the ones discussed in the StringBuffer/StringBuilder section in chapter 6.

The charAt() and setCharAt() methods were never discussed in the context of StringBuffers/StringBuilders in Chapter 6.
[ June 20, 2007: Message edited by: Brad Clarke ]

[Louie Cheung]

Originally posted by Giovanni Murguia:
Hello!

You could try something like:

  
char letter = buffer.charAt(0);
buffer.setCharAt(0, letter+1);

Giovanni

i'm getting compiler error for the above code as follows:

cannot find symbol
symbol : method setCharAt(int, int)
location: class java.lang.StringBuffer
sb.setCharAt(0, letter+1);

i tested if i change it to the following it compiles fine:
sb.setCharAt(0, letter);

so what's wrong with the +1 there?