翻转字符串里的单词

class Solution {
    public String reverseWords(String s) {
       StringBuilder sb=removeSpace(s);
       reverse(sb,0,sb.length()-1);
       reverseEach(sb);
       return sb.toString();
    }
    public StringBuilder removeSpace(String s)
    {
        int start=0;
        int end=s.length()-1;
        while(s.charAt(start)==' ') start++;
        while(s.charAt(end)==' ') end--;
        StringBuilder sb=new StringBuilder();
        while(start<=end)
        {
            char c=s.charAt(start);
            if(c!=' '||sb.charAt(sb.length()-1)!=' ')
            {
                sb.append(c);
            }
            start++;
        }
        return sb;
    }
    public void reverse(StringBuilder sb,int start,int end)
    {
        while(start<end)
        {
            char temp=sb.charAt(start);
            sb.setCharAt(start,sb.charAt(end));
            sb.setCharAt(end,temp);
            start++;
            end--;
        }
    }
    public void reverseEach(StringBuilder sb)
    {
        int start=0;
        int end=1;
        while(start<sb.length())
        {
            while(end<sb.length()&&sb.charAt(end)!=' ')
            {
                end++;
            }
            reverse(sb,start,end-1);
            start=end+1;
            end=start+1;
        }
    }
}