com.darwinsys.lang.StringFormat Maven / Gradle / Ivy
package com.darwinsys.lang;
import java.text.FieldPosition;
import java.text.Format;
import java.text.ParsePosition;
/** Bare-minimum "String formatter": format a string to a given
* maximum length with left, centre, or right justification.
*/
public class StringFormat extends Format {
private static final long serialVersionUID = 3257571702421402417L;
/* Constant for left justification. */
public static final int JUST_LEFT = 'l';
/* Constant for centering. */
public static final int JUST_CENTRE = 'c';
/* Constant for centering, for those who spell "centre" the American way. */
public static final int JUST_CENTER = JUST_CENTRE;
/** Constant for right-justified Strings. */
public static final int JUST_RIGHT = 'r';
/** Current justification */
private int just;
/** Current max length */
private int maxChars;
public StringFormat(int maxCh, int justn) {
switch(justn) {
case JUST_LEFT:
case JUST_CENTRE:
case JUST_RIGHT:
this.just = justn;
break;
default:
throw new IllegalArgumentException("invalid justification arg.");
}
if (maxCh < 1) {
throw new IllegalArgumentException("maxChars must be positive.");
}
this.maxChars = maxCh;
}
/** Format a String */
public StringBuffer format(
Object obj, StringBuffer where, FieldPosition ignore) {
String s = (String)obj;
String wanted = s.substring(0, Math.min(s.length(), maxChars));
// If no space left for justification, return maxChars' worth */
if (wanted.length() > maxChars) {
where.append(wanted);
}
// Else get the spaces in the right place.
else switch (just) {
case JUST_RIGHT:
pad(where, maxChars - wanted.length());
where.append(wanted);
break;
case JUST_CENTRE:
int startPos = where.length();
pad(where, (maxChars - wanted.length())/2);
where.append(wanted);
pad(where, (maxChars - wanted.length())/2);
// Adjust for "rounding error"
pad(where, maxChars - (where.length() - startPos));
break;
case JUST_LEFT:
where.append(wanted);
pad(where, maxChars - wanted.length());
break;
}
return where;
}
protected final void pad(StringBuffer to, int howMany) {
for (int i=0; i