Bitwise & Operator and This Boolean Method

[applejuice]

Hi: Could someone tell me whats going on in this method? what is that bitwise '&' operator doing in a if conditional statement? does this method always return 'False'/'True'? Where is the 'Else' Statement? What Happens when the if statemet becomes False, would the rest of the code be processed? Wouldn't return be the last line of the code? Sorry I'm a java newbie.

  private boolean hasWLMData(){
	String curLine;  //current line to read

	while (!in.eofIsAvailable()){                           //while not at the end of the file
	  curLine = in.readLine();                              //read the first word of the current line
	  if(curLine !="" && curLine != null & curLine.substring(0,3).equals("WLM")){             //first 3 chars of the word are "WLM"?
		  in.close();                                       //close input file
		  in = new TextInput(filePath);                     //reset the in so our read head is at the start of file.
		  return true;                                      //yes, we have found WLM information in the nmon report
	  }
	}
	in.close();                                            //close the input file
	in = new TextInput(filePath);                          //open the input file again (restarts read head after scanning through)
	return false;
  }

[destin]

The way you are using it, it is not a bitwise operator. It is a conditional one. It means AND. There are two ways to say AND in Java, either && or &. && does something called short-circuit evaluation. This means that if the first one is false, it will break imidiately. eg:

String s;
int len;
if (s != null && s.length() > 0) {
    len = s.length();
}

What happens here, is if s is null, it imediately knows this condition is false. This code will always work. This, however, will not:

String s;
int len;
if (s != null & s.length() > 0) {
    len = s.length();
}

Here, if s is null, it will still evaluate the second part of the condition and a NullPointerException will be thrown.

The bitwise operator & is used for computation with ints.

  if(curLine !="" && curLine != null & curLine.substring(0,3).equals("WLM")){             //first 3 chars are WLM?

This should be simplified to:

if (curLine != null && curLine.startsWith("WLM")) {

Note that I used && rather than &, and I got rid of curLine != "". That's a silly comparison; it will never be true. It will check if the memory of the String "" that was just created has the same as curLine.

Hope this helps.

[applejuice]

wow. you are awesome man. thanks a bunch

[Kinda Electroni]

This should be simplified to:

if (curLine != null && curLine.startsWith("WLM")) {

Note that I used && rather than &, and I got rid of curLine != "". That's a silly comparison; it will never be true. It will check if the memory of the String "" that was just created has the same as curLine.

Hope this helps.

I am sorry to interfere, but if it is useless; why it is there?
Just I would like to learn.

[destin]

I am sorry to interfere, but if it is useless; why it is there?
Just I would like to learn.

If what is useless?