Truncating/ Padding a string

[marcus conway]

Hey,

I'm having some trouble creating a method (in the form.....

public static String padString ( String s, int width, char alignment )

)

that positions string s in a field of a desired width. If the string is longer than the desired field width, it will need to be truncated. If it is shorter than the desired field width it will need to be padded with blank characters. The alignment parameter determines whether the string will be left aligned ('L' or 'l') in the field (padding added to the right) or right aligned ('R' or 'r') in the field (padding added to the left). And if there are not enough spaces to display the string, at least one space must be provided on the appropriate side.

I've been playing around with it:

public static String padString ( String s, int width, char alignment ){
if (alignment == 'L' || alignment == 'l'){
System.out.println("pad to the left " + width + " units.");
int space = width;
int spNeeded = s.length();
int truncate = (width - spNeeded);
System.out.println("width: "+width+" spaces: "+space);
for (int i = 0; i < width; i++ ){
System.out.print(s );
}
System.out.println(s);
truncate +=1;
System.out.println("truncate: " + truncate);
 
int sLeng = s.length();
System.out.println("string length: "+ sLeng);
s = s.substring(0, (sLeng-1));
System.out.println(s);
}
else if (alignment == 'R' || alignment == 'r'){
boolean right = true;
boolean left = false;
System.out.println("pad to the right " + width + " units.");
for (int i = 0; i < width; i++ ){
System.out.print(" ");
}
}
return s;
}

And I've been testing it in various ways. But ultimately the I/O should look similar to this:

s = "Hello", width = 5, leftRight='L' ⇒ return string is "Hell "
s = "Hello", width = 10, leftRight='R' ⇒ return string is "     Hello"

I've been struggling with this for quite some time now, so any help would be greatly appreciated.

Thanks,

n

[marc weber]

I think it might be helpful for you to describe the steps you want to follow (your algorithm) in English before trying to code it in Java. Once you have the logical steps clear, it will be much easier to code.

For example, you might say something like this:
1) Determine whether the String will fit in the given space.
2) If it will fit, then...
3) If it will not fit, then...
etc.

[Christophe Verré]

Of course, you are not allowed to use String.format ?

[Campbell Ritchie]

Originally posted by Christophe Verre:
Of course, you are not allowed to use String.format ?

Or, it might be better still to use a StringBuilder.