Outputting a leading zero an int variable

Question

I'm trying to output a series binary digits and next series of binary digits depend on the previous series's of binary digits. Some of these series lead with one or more zeroes. I can only use int variables.

So if the program starts with 0, the next output will be 01 and then 0110 and so on. Will I have to hard code a leading a zero if the int starts with a zero or is there another way I can do this?

Also, is Integer.toBinaryString() the only way to output a number to binary?

http://stackoverflow.com/questions/473282/left-padding-integers-with-zeros-in-java — zbrunson, Nov 27 '12 at 17:59
Nope. An integer is an integer is an integer; leading zeroes don't make a number special (except that they make a literal octal). — Louis Wasserman, Nov 27 '12 at 18:01
Your edit makes the question much worse. `01` is actually `1`, but `01101001` is `295425`, and printing it with a leading 0 is definitely not what you want to do. — Wooble, Nov 28 '12 at 15:15

Jack · Answer 1 · 2012-11-27T18:07:21.040

3

Just format the output, you syntax is meaningless because the value of 01 is 1, the compiler just store the value as a number, not as a sequence of digits. Try with:

int x = 1;
System.out.printf("%02d", x);

To be more precise when you place a leading 0 the number literal is interpreted as octal (base 8). So for 01 it's ok but 08 would be illegal (since 8 is not a valid octal digit). This is true for many programming languages.

In any case don't confuse a number literal with a numeric value. The compiler turns a literal into a value and just the value is what is effectively used at runtime.

edited Nov 27 '12 at 18:07

answered Nov 27 '12 at 18:02

Jack

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Louis Wasserman said it best above: "An integer is an integer is an integer; leading zeroes don't make a number special". IMPORTANT POINT: a leading "0" is a "literal octal". The literal "07" is "7". The literal "010" is "8". The literal "08" is illegal. – paulsm4 Nov 27 '12 at 18:04

ppeterka · Answer 2 · 2012-11-27T18:07:24.743

If your problem is really just this simple, then you should try this:

System.out.print("0"+x);

As you may be aware of, integer stores values. And what gets output to the screen is converted to be Strings. An integer is going to be converted to a tring without the leading zeroes.

By the way, if you start a numeric constant with a 0, in Java that means that you are specifying an octal number.

Recommended reading: Java literals

If however your problem is deeper, like you should output numbers in given formats, you should definitely read up on DecimalFormat

System.out.println(new DecimalFormat("00").format(x));

Mark Byers · Answer 3 · 2012-11-27T18:05:48.410

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The type int just stores an numeric integer value and nothing more. An int variable does not store the leading zeros, nor the base in which the number was entered. In your case the leading zero means an octal literal, which is probably not what you meant anyway.

If you want to store the leading zeros you have to do using a different approach, for example using a string as you suggest.

edited Nov 27 '12 at 18:05

answered Nov 27 '12 at 18:00

Mark Byers

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Newmangamers · Answer 4 · 2012-11-27T18:23:54.550

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As far as i know, no because java trys to save ram usage by removing un-needed 0's. The best way would be to create it into a string and create a method that can times, add, take away, devide a string integer by a string integer(times no's and then readd the 0's to the start).

EDIT

public String addStringInteger(String x1, Integer i){
    String leading0 = "";
    String nol = "";
    boolean onLeading = true;
    for(char c : x1.toCharArray()){
        String l = Character.toString(c);
        if(onLeading && l.equals("0")){
            leading0 += "0";
        }else{
            onLeading = false;
            nol += l;
        }
    }
    int intO = Integer.parseInt(nol) + i; //you can change + to x, -, / etc
    return leading0 + ""+ intO;
}

this example would allow you to do addStringInteger("001", 20) and you would get 0021 back, the method could be edited so you get 021 back, but i made that as a quick example, this sort of method should be able to perform anything.

edited Nov 27 '12 at 18:23

answered Nov 27 '12 at 18:03

Newmangamers

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RAM usage? RAM usage is irrelevant in this context. The problem is that a number literal is parsed into a numeric value, they are not the same thing. 01 or 1 are both parsed to 1 (excluding the fact that 0 usually specifies an octal number) – Jack Nov 27 '12 at 18:04
EDIT: Oops, the snark just leaped forth into the textbox. De-snarked. – chucksmash Nov 27 '12 at 18:11
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Excuse me, but it still does not make any more sense than it did before... Why do something manually, when you have the tools to do it nice? – ppeterka Nov 27 '12 at 18:42

Outputting a leading zero an int variable

4 Answers4