oglimmer/utils

package de.oglimmer.utils.random;

import java.util.Random;

/**
 * Creates various random strings while the user can define length and characters.
 * 
 * @author Oli Zimpasser
 */
final public class RandomString {

    private RandomString() {
        // no code here
    }

    private static final Random RAN = new Random(System.currentTimeMillis());

    /**
     * Creates a size byte long unicode string. All codes are >= start and < start+length
     *
     * @param size number of characters in the return string
     * @param start start code
     * @param length all generated codes are within this range
     * @return
     */
    public static String getRandomString(final int size, final int start, final int length) {
        final StringBuilder buff = new StringBuilder(size);

        for (int i = 0; i < size; i++) {
            buff.append((char) (RAN.nextInt(length) + start));
        }
        return buff.toString();
    }
    
    /**
     * Creates a size byte long unicode string. All codes are &gt;= 32.
     * 
     * @param size
     *            number of characters in the return string
     * @return a random string build from unicode characters
     */
    public static String getRandomStringUnicode(final int size) {
        return getRandomString(size, 32, 65503);
    }

    /**
     * Creates a size byte long unicode string. All codes are between 32 and 255
     * 
     * @param size
     *            number of characters in the return string
     * @return a random string build from ASCII 32 ... 255
     */
    public static String getRandomString8Bit(final int size) {
        return getRandomString(size, 32, 223);
    }

    /**
     * Creates a size byte long unicode string. All codes are between a..z and A..Z and 0..9
     * 
     * @param size
     *            number of characters in the return string
     * @return a random string build from a..z and A..Z and 0..9
     */
    public static String getRandomStringASCII(final int size) {
        return getRandomString(size, "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz");
    }

    /**
     * Creates a size byte long unicode string. All codes are from the set "stringSet"
     * 
     * @param size
     *            number of characters in the return string
     * @param stringSet
     *            set of characters used for string creation
     * @return a random string build from "stringSet"
     */
    public static String getRandomString(final int size, final String stringSet) {

        final StringBuilder buff = new StringBuilder(size);

        for (int i = 0; i < size; i++) {
            final char nextChar = stringSet.charAt(RAN.nextInt(stringSet.length()));
            buff.append(nextChar);
        }
        return buff.toString();
    }

    /**
     * Creates a size byte long unicode string. All codes are 0..9 and a..f.
     * 
     * @param size
     *            number of characters in the return string
     * @return a random string build from 0..9 and a..f (a valid hex)
     */
    public static String getRandomStringHex(final int size) {
        return getRandomString(size, "0123456789ABCDEF");
    }

}