A nascent collection of String utilities.

Strings.java

package com.n1nja.utils;
/**
 * Useful classes for manipulating {@link java.lang.String String}s.
 * @author Colin Haber
 * @version 0.0.0
 */
public class Strings {
	/**
	 * The default {@code char} used for padding 
	 * {@link java.lang.String String}s.
	 * @since 0.0.0
	 * @see #pad(String, int, String, boolean)
	 */
	private static char DEFAULT_PAD_CHAR = ' ';
	/**
	 * The default side to pad from.
	 * @since 0.0.0
	 * @see #pad(String, int, String, boolean)
	 */
	private static boolean DEFAULT_PAD_SIDE = Strings.PAD_START;
	/**
	 * Indicates padding should be done from the left.
	 * @since 0.0.0
	 * @see #pad(String, int, String, boolean)
	 */
	public static final boolean PAD_START = true;
	/**
	 * Indicates padding should be done from the right.
	 * @since 0.0.0
	 * @see #pad(String, int, String, boolean)
	 */
	public static final boolean PAD_END = false;
	/**
	 * Pads a {@link java.lang.String String} from the left with spaces.
	 * @since 0.0.0
	 * @param s the {@link java.lang.String String} to pad
	 * @param len the amount of spaces to pad with
	 * @return the padded {@link java.lang.String String}
	 */
	public static String pad(String s, int len) {
		return Strings.pad(s, len, Strings.DEFAULT_PAD_CHAR);
	}
	/**
	 * Pads a {@link java.lang.String String} from the left with the provided 
	 * {@code char}.
	 * @since 0.0.0
	 * @param s the {@link java.lang.String String} to pad
	 * @param len the amount of {@code char}s to pad with
	 * @param pad the {@code char} to pad with
	 * @return the padded {@link java.lang.String String}
	 */
	public static String pad(String s, int len, char pad) {
		return Strings.pad(s, len, Character.toString(pad));
	}
	/**
	 * Pads a {@link java.lang.String String} from the left with the provided 
	 * {@code char}.
	 * @since 0.0.0
	 * @param s the {@link java.lang.String String} to pad
	 * @param len the amount of {@code char}s to pad with
	 * @param pad the {@link java.lang.String String} to pad with
	 * @return the padded {@link java.lang.String String}
	 */
	public static String pad(String s, int len, String pad) {
		return Strings.pad(s, len, pad, Strings.DEFAULT_PAD_SIDE);
	}
	/**
	 * Pads a {@link java.lang.String String} from the left with the provided 
	 * {@code char}.
	 * @since 0.0.0
	 * @param s the {@link java.lang.String String} to pad
	 * @param len the amount of {@code char}s to pad with
	 * @param side the side to pad from
	 * @return the padded {@link java.lang.String String}
	 */
	public static String pad(String s, int len, boolean side) {
		return Strings.pad(s, len, Strings.DEFAULT_PAD_CHAR, side);
	}
	/**
	 * Pads a {@link java.lang.String String} from the left with the provided 
	 * {@code char}.
	 * @since 0.0.0
	 * @param s the {@link java.lang.String String} to pad
	 * @param len the amount of {@code char}s to pad with
	 * @param pad the {@code char} to pad with
	 * @param side the side to pad from
	 * @return the padded {@link java.lang.String String}
	 */
	public static String pad(String s, int len, char pad, boolean side) {
		return Strings.pad(s, len, Character.toString(pad), side);
	}
	/**
	 * Pads a {@link java.lang.String String} from the left with the provided 
	 * {@code char}.
	 * @since 0.0.0
	 * @param s the {@link java.lang.String String} to pad
	 * @param len the amount of {@code char}s to pad with
	 * @param pad the {@link java.lang.String String} to pad with
	 * @param side the side to pad from
	 * @return the padded {@link java.lang.String String}
	 */
	public static String pad(String s, int len, String pad, boolean side) {
		if (len < 0) {
			throw new IllegalArgumentException("Cannot pad negative lengths.");
		} else if (s.length() <= 0 || pad.length() <= 0) {
			throw new IllegalArgumentException("Cannot have zero-length Strings.");
		}
		StringBuilder padder = new StringBuilder(Math.max(s.length(), len));
		int padlen = len - s.length();
		if (side == Strings.PAD_START) {
			padder.append(s);
			padlen = len;
		}
		char[] padChars = pad.toCharArray();
		int i = 0;
		while (padder.length() < padlen) {
			padder.append(padChars[i]);
			i++;
			if (i >= padChars.length) {
				i = 0;
			}
		}
		if (side == Strings.PAD_END) {
			padder.append(s);
		}
		return padder.toString();
	}
	/**
	 * Repeats a {@link java.lang.String String} until it reaches length 
	 * {@code len}. For example, {@code repeat("tittysprinkles", 20)} would 
	 * return {@code "tittysprinklestittys"}.
	 * @param s the {@link java.lang.String String} to be repeated
	 * @param len the target length
	 * @return a {@link java.lang.String String} length {@code len}, containing 
	 * {@code s} repeated until the target length.
	 */
	public static String repeat(String s, int len) {
		if (len < 0) {
			throw new IllegalArgumentException("Cannot repeat negative lengths.");
		} else  if (s.length() <= 0) {
			throw new IllegalArgumentException("Cannot have zero-length Strings.");
		}
		StringBuilder repeater = new StringBuilder(len);
		do {
			repeater.append(len - repeater.length() > s.length() ? s : s.substring(0, len - repeater.length()));
		} while (repeater.length() < len);
		return repeater.toString();
	}
}