Java - Write code to shrink multiple spaces to one

Requirements

Write code to shrink multiple spaces to one

Demo

//package com.book2s;

public class Main {
    public static void main(String[] argv) {
        String str = "book2s.com";
        System.out.println(space2one(str));
    }//from  w  ww.  j  av a  2  s  .  c o m

    public static String space2one(String str) {
        if (null != str) {
            str = removeInvisible(str).trim();
        }
        if (null != str && !str.trim().isEmpty()) {
            return str.trim().replaceAll("[\\s\\r\\n]{1,1500}", " ");
        } else {
            return str != null ? str.trim() : null;
        }
    }

    public static String removeInvisible(String str) {
        if (null != str) {
            str = str.trim();
            StringBuilder newString = new StringBuilder(str.length());
            for (int offset = 0; offset < str.length();) {
                int codePoint = str.codePointAt(offset);
                offset += Character.charCount(codePoint);
                switch (Character.getType(codePoint)) {
                case Character.CONTROL: // \p{Cc}
                case Character.FORMAT: // \p{Cf}
                case Character.PRIVATE_USE: // \p{Co}
                case Character.SURROGATE: // \p{Cs}
                case Character.UNASSIGNED: // \p{Cn}
                case Character.OTHER_SYMBOL: // \OTHER_SYMBOL
                case Character.SPACE_SEPARATOR: // \SPACE_SEPARATOR
                    newString.append(' ');
                    break;
                default:
                    newString.append(Character.toChars(codePoint));
                    break;
                }
            }
            return newString.toString();
        } else {
            return "";
        }
    }
}