JAva文字列反転

Stringはi love youに反転してyou love iになる

    public void test(){
        String str = "i love you";
        StringBuilder sb = new StringBuilder(str);
        str = sb.reverse().toString();
        char[] ch = str.toCharArray();
        int begin = 0,end=0;
        for(;endend++){
            if(ch[end]==' '){
                reverse(ch,begin,end-1);
                begin = end+1;
            }

        }
        reverse(ch,begin,end-1);
        System.out.println(ch);

    }
    public void reverse(char[] str,int begin,int end){
        while(begin<end){
            char tmp = str[begin];
            str[begin] = str[end];
            str[end] = tmp;
            begin++;
            end--;

        }
    }