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package com.battcn.boot.request.utils;

/**
 * @author Levin
 * @since 2018/12/20 0020
 */
public class StringUtils {

    /**
     * The empty String {@code ""}.
     *
     * @since 2.0
     */
    public static final String EMPTY = "";

    public static final String DEFAULT_CHARSET = "UTF-8";

    /**
     * Returns either the passed in String, or if the String is
     * {@code null}, the value of {@code defaultStr}.
     * 
     * 
     * StringUtils.defaultString(null, "NULL")  = "NULL"
     * StringUtils.defaultString("", "NULL")    = ""
     * StringUtils.defaultString("bat", "NULL") = "bat"
     * 
     *
     * @param str        the String to check, may be null
     * @param defaultStr the default String to return
     *                   if the input is {@code null}, may be null
     * @return the passed in String, or the default if it was {@code null}
     * @see String#valueOf(Object)
     */
    public static String defaultString(final String str, final String defaultStr) {
        return str == null ? defaultStr : str;
    }


    /**
     * Joins the elements of the provided array into a single String
     * containing the provided list of elements.
     * 
     * 
No separator is added to the joined String.
     * Null objects or empty strings within the array are represented by
     * empty strings.
     * 
     * 
     * StringUtils.join(null)            = null
     * StringUtils.join([])              = ""
     * StringUtils.join([null])          = ""
     * StringUtils.join(["a", "b", "c"]) = "abc"
     * StringUtils.join([null, "", "a"]) = "a"
     * 
     *
     * @param       the specific type of values to join together
     * @param elements the values to join together, may be null
     * @return the joined String, {@code null} if null array input
     * @since 3.0 Changed signature to use varargs
     */
    public static  String join(final T... elements) {
        return join(elements, null);
    }

    /**
     * Joins the elements of the provided array into a single String
     * containing the provided list of elements.
     * 
     * 
No delimiter is added before or after the list.
     * Null objects or empty strings within the array are represented by
     * empty strings.
     * 
     * 
     * StringUtils.join(null, *)               = null
     * StringUtils.join([], *)                 = ""
     * StringUtils.join([null], *)             = ""
     * StringUtils.join(["a", "b", "c"], ';')  = "a;b;c"
     * StringUtils.join(["a", "b", "c"], null) = "abc"
     * StringUtils.join([null, "", "a"], ';')  = ";;a"
     * 
     *
     * @param array      the array of values to join together, may be null
     * @param separator  the separator character to use
     * @param startIndex the first index to start joining from.  It is
     *                   an error to pass in an end index past the end of the array
     * @param endIndex   the index to stop joining from (exclusive). It is
     *                   an error to pass in an end index past the end of the array
     * @return the joined String, {@code null} if null array input
     * @since 2.0
     */
    public static String join(final Object[] array, final char separator, final int startIndex, final int endIndex) {
        if (array == null) {
            return null;
        }
        final int noOfItems = endIndex - startIndex;
        if (noOfItems <= 0) {
            return EMPTY;
        }
        final StringBuilder buf = new StringBuilder(noOfItems * 16);
        for (int i = startIndex; i < endIndex; i++) {
            if (i > startIndex) {
                buf.append(separator);
            }
            if (array[i] != null) {
                buf.append(array[i]);
            }
        }
        return buf.toString();
    }

}