How to use boolean?

[Ls chin]

Hi all,

I came across this code but I don't understand it. Especially the boolean part. What does it mean when CR is set to true? Why must we check (CR == false) in the else statement, isn't it redundant?

Can we avoid using 'nested if' in this code? How to re-write it?

import java.util.*;
 
public class DisplayWords {
    static Scanner myScanner = new Scanner(System.in);
    
    public static void main(String[] args) {     
        String text;    
        int i; 
        char c;         
        boolean CR;  
           
        System.out.println("Enter your text here: ");
        text = myScanner.nextLine();
          
        CR = true;   
        
        for (i = 0; i < text.length(); i++) {
           c = text.charAt(i);              
           if (Character.isLetter(c)) {
              System.out.print(c);      
              CR = false;
           }
           else {
              if (CR == false) {
                 System.out.println();
                 CR = true;
              }
           }
        }                          
    }  
 }  

Thank you in advance.

[Gamini Sirisena]

Looks like if (CR == false) makes a new line print only if a letter is printed. Otherwise a new line will be printed for all letters and non letters.

[Campbell Ritchie]

Never use == false or == true. You write if (CR) . . .

And don't use all capital letters for that CR variable, for two reasons.

Java conventions use mixed case for identifiers (exception "constants").

I thought you were talking about me

If you make a mistake and write = false instead of == false, you can get all sorts of nasty errors later on in the program.

[Campbell Ritchie]

You are right that the CR variable is redundant; you can simply write

   if(Character.isLetter(c))
   {
       System.out.print(c);
   }
   else
   {
       System.out.println();
   }

and you don't need to declare any boolean variables.

[Joanne Neal]

Originally posted by Campbell Ritchie:
You are right that the CR variable is redundant; you can simply write

   if(Character.isLetter(c))
   {
       System.out.print(c);
   }
   else
   {
       System.out.println();
   }

and you don't need to declare any boolean variables.

If you have more than one consecutive non-letter character, this code will print a newline for each one. The OP's code would only print one

[Campbell Ritchie]

Yes, you're right, Joanne. Thank you. I missed that.

[Ilja Preuss]

You can avoid the nested if by using the continue statement. Whether that's better is open to personal preference.

for (i = 0; i < text.length(); i++) {
  c = text.charAt(i);
  if (Character.isLetter(c)) {
    System.out.print(c);
    CR = false;
    continue;
  }
  if (CR == false) {
    System.out.println();
    CR = true;
  }
}            

[Seetharaman Venkatasamy]

Originally posted by Ilja Preuss:
if (CR == false)

Again you repeated the same thing which is redundant

[Joanne Neal]

Originally posted by seetharaman venkatasamy:


Again you repeated the same thing which is redundant

See my first reply.

[Ilja Preuss]

Originally posted by seetharaman venkatasamy:


Again you repeated the same thing which is redundant

It's not redundant.

I apologize for using "CR == false" instead of "!CR", though. Copy'n'paste... :roll:

[Ls chin]

Thanks to everyone who replied, it' much appreciated.

Originally posted by Campbell Ritchie:
Never use == false or == true. You write if (CR) . . .
[/code]
Understood.

[code]
And don't use all capital letters for that CR variable, for two reasons.

Java conventions use mixed case for identifiers (exception "constants").

I thought you were talking about me

If you make a mistake and write = false instead of == false, you can get all sorts of nasty errors later on in the program.

Ok, got it.

[Ls chin]

Originally posted by Ilja Preuss:

for (i = 0; i < text.length(); i++) {
  c = text.charAt(i);
  if (Character.isLetter(c)) {
    System.out.print(c);
    CR = false;
    continue;
  }
  if (!CR) {
    System.out.println();
    CR = true;
  }
}            

This code looks neater than the 'nested if' one. Thanks.

[ October 28, 2008: Message edited by: LS chin ]

[Campbell Ritchie]

Can't you get rid of the "continue" (I am one of those people who don't like it) by using else if (!CR) . . .?

[Ilja Preuss]

Originally posted by Campbell Ritchie:
Can't you get rid of the "continue" (I am one of those people who don't like it) by using else if (!CR) . . .?

Yes.

Another possibility is to move the if/else into a Method Object and the use return instead of continue.