Initializing variable inside a while-loop

Question

I have a program in which I need to read a file word by word and save this in a String variable. This works fine (I use a while loop), but the problem is that my string variable doesn't have the same value outside the loop. If I check what the variable contains inside the while loop, I get over 30000 words, but when I try the same thing outside the while-loop, only 1 word comes up.

String ord = null;
while (fil.hasNext()) {
    ord = leser.next();
    System.out.println(ord); //If I print it here I get the whole file
}
System.out.println(ord); // If i try to print out the content here, I only get 1 word

I don't understand why the variable "ord" doesn't contain the same inside and outside the loop, and how can I fix this? I of course need this variable in other places in my program, but since there is only 1 word stored, the rest of my program doesn't work as intended.

You are just getting the last word read outside the loop. Inside loop, words are printed on different iteration. You should add them to a list, or create a StringBuilder by concatenating them. — Rohit Jain
– Rohit Jain, Commented Oct 4, 2013 at 9:32

Duncan Jones · Accepted Answer · 2013-10-04 09:31:56Z

4

The value of ord is constantly changing. Because you choose to print it each time during the loop, you believe it contains the entire file.

You could instead use a StringBuilder and append strings to that.

StringBuilder builder = new StringBuilder();
while (fil.hasNext()) {
    String tmp = leser.next();
    System.out.println(tmp); // If still needed
    builder.append(tmp);
}

String completeString = builder.toString();

answered Oct 4, 2013 at 9:31

Duncan Jones

69.7k32 gold badges204 silver badges262 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Prasad · Accepted Answer · 2013-10-04 09:46:12Z

1

ord is re-initializing inside while loop.So in final iteration of while loop, ord contains the last word present in leser.next().

do one thing

String ord = null;

StringBuffer str = new StringBuffer();

while (fil.hasNext()) {

    ord = leser.next();
    System.out.println(ord);
    str.append(ord); //To retain the value of ord for future use.

}

System.out.println(str.toString);

edited Oct 4, 2013 at 9:46

Prasad

1,1883 gold badges11 silver badges29 bronze badges

answered Oct 4, 2013 at 9:38

AJ.

4,5355 gold badges32 silver badges43 bronze badges

Comments

Suresh Atta · Accepted Answer · 2013-10-04 10:06:59Z

1

You variable keep reassigning and you are getting the last one.

Starting from here,

String ord = null;

// Started executing 
    while (fil.hasNext()) {
        ord = leser.next();
        System.out.println(ord); 
    }
//Ended executing

Now in the   ord  last assigned value is there 

System.out.println(ord);

Where as inside

 // Started executing 
        while (fil.hasNext()) {
            ord = leser.next();      //new  value  assigned
            System.out.println(ord); // new value printed
        }
    //Ended executing

What you can do is store the previous value also.

   StringBuilder builder = new StringBuilder ();     
    // Started executing 
        while (fil.hasNext()) {

            builder.append(leser.next()); //append to previous val
            builder.append(System.getProperty("line.separator"));
        }
    //Ended executing
    System.out.println(builder.toString());

edited Oct 4, 2013 at 10:06

answered Oct 4, 2013 at 9:31

Suresh Atta

122k38 gold badges206 silver badges315 bronze badges

3 Comments

user2795095 Over a year ago

Thanks, this worked well :) Only one question, now all the words are written out all in one chunk, whereas before they were written out one on each line. Is there any way to do this with StringBuilder?

Suresh Atta Over a year ago

@user2795095 yes. you can append a new line after each append. I'l update my post. Please look at my update

user2795095 Over a year ago

Great, now I got it word for word. Thank you :)

Juned Ahsan · Accepted Answer · 2013-10-04 09:33:00Z

0

variable ord contains only one value both inside and outside the loop. Inside the loop its value keep getting reassigned and printed. But outside the loop it will have the last value set in loop.

answered Oct 4, 2013 at 9:33

Juned Ahsan

68.9k12 gold badges101 silver badges138 bronze badges

Comments

Gurminder Singh · Accepted Answer · 2013-10-04 09:33:38Z

0

You can use StringBuffer instead like

StringBuffer ord = new StringBuffer;
while (fil.hasNext()) {
   ord.append(leser.next());
}
System.out.println(ord.toString());

answered Oct 4, 2013 at 9:33

Gurminder Singh

1,75516 silver badges19 bronze badges

1 Comment

Duncan Jones Over a year ago

StringBuilder is usually preferred, unless one has a need for thread safety (and the overheads that causes).

Boris the Spider · Accepted Answer · 2013-10-04 09:34:25Z

0

You reassign the variable ord every iteration.

It's clearest seen without the while loop, what you are doing is:

String ord = "test";
ord = "another string";

So the value of ord is simply changed. You need to store the values in a List:

List<String> ord = new LinkedList<>();
while (fil.hasNext()) {
    ord.add(leser.next());
}
System.out.println(ord);

answered Oct 4, 2013 at 9:34

Boris the Spider

61.4k6 gold badges111 silver badges177 bronze badges

Comments

Masudul · Accepted Answer · 2013-10-04 09:35:32Z

0

why the variabel "ord" don't contain the same inside and outside the loop?

Because, String is immutable. Every step of while loop it generate new reference and previous reference of ord is lost.

and how can I fix this?

If you use StringBuilder instead of String and append the content inside while loop than you will see the whole file output outside of while loop.

answered Oct 4, 2013 at 9:35

Masudul

22k5 gold badges45 silver badges60 bronze badges

Comments

Orel Bitton · Accepted Answer · 2013-10-04 09:37:26Z

As you can see, your are reading the file word by word, and each time your are set the ord variable to the current word:

String ord = null;
while (fil.hasNext()) {
     /*if the next word exist - lets set ord to the next word, means 
     each time the ord variable changes to the next word. */
    ord = leser.next();
    System.out.println(ord);
}
System.out.println(ord); //will print the last word in the file

If you want to save the whole file inside the ord variable, you could do something like this:

String ord = null;
while (fil.hasNext()) {
     /*if the next word exist - lets set ord to the ord variable 
     content + the next word, means we are just adding the next word*/
    ord = ord + leser.next();
    System.out.println(ord); //print current word
}
System.out.println(ord); //will print the whole file

Collectives™ on Stack Overflow

Initializing variable inside a while-loop

8 Answers 8

Comments

Comments

3 Comments

Comments

1 Comment

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

8 Answers 8

Comments

Comments

3 Comments

Comments

1 Comment

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related