Java 替换空格

实现1

 /**
     * 替换空格
     * @param s
     * @param re
     * @return
     */
    public String replaceSpace(String s,String re ) {
        // write code here

        StringBuilder builder = new StringBuilder();
        for (char c : s.toCharArray()) {
            builder.append(c == ' ' ? re : c);
        }
        return builder.toString();

    }

实现2

 public String replaceSpace(String s,String relacement) {
        // write code here
        return s.replaceAll(" ", relacement);
    }

实现3

 public String replaceSpace(String s) {
        // 字符串的实际长度
        int length = s.length();
        // 字符串转换为字符数组
        char[] chars = s.toCharArray();
        // 统计字符串空格的数量
        int  numberOfBlank = 0;
        for (char c : chars) {
            if (c == ' '){
                numberOfBlank++;
            }
        }
        // 新数组的长度
        int newLength = length +2*numberOfBlank;
        char[] ch = new char[newLength];
        // 数组中的空格替换为指定字符 本例为%20
        for (int i = 0,j = 0; i < length; i++) {
            if (chars[i] != ' '){
                ch[j++] = chars[i];
            }else{
                ch[j++] = '%';
                ch[j++] = '2';
                ch[j++] = '0';
            }
        }
        return new String(ch);
    }